Patent Application
20140246227
1. Field of the Invention
The present invention relates to a method of making a cavity substrate and a cavity substrate manufactured thereby, and more particularly to a method of making a cavity substrate with a via opening exposed from a cavity defined by a bump/flange sacrificial carrier and a cavity substrate manufactured thereby.
2. Description of Related Art
Latest trends of electronic devices such as mobile internet devices (MIDs), multimedia devices and computer notebooks demand for faster and slimmer designs. In the frequency band of a general signal, the shorter paths of circuitry, the better the signal integrity. Thus, the size of inter-layer connection, i.e., the diameter of the micro-via and plated through hole in the substrate must be reduced in order to improve the signal delivery characteristic of the electronic component. As plated-through-hole in the copper-clad laminate core is typically formed by mechanical CNC drill, reducing its diameter in order to increase wiring density may encounter seriously technical limitations and often very costly. As such, coreless substrates are proposed for packaging substrate to enable a thinner, lighter and faster design of the components. However, as coreless boards do not have a core layer to provide a necessary flexural rigidity, they are more susceptible to warpage problem when under thermal stress compared to that of conventional boards with core layers.
U.S. Pat. No. 7,164,198 to Nakamura et al., U.S. Pat. No. 7,400,035 to Abe et al., U.S. Pat. No. 7,582,961 to Chia et al., U.S. Pat. No. 7,934,313 to Lin et al. disclose a coreless packaging substrate with built-in stiffener by etching a portion of a metal sheet on which the build-up circuitry is formed. The built-in stiffener defines a cavity which serves as the region for semiconductor device attachment. In this approach, although a supporting platform can be created and warping issues may be improved, etching a thick metal block is prohibitively cumbersome, low throughput, and prone to create many yield-loss issues such as an uncontrollable boundary line due to etching under-cut.
U.S. Pat. No. 8,108,993 to Higashi et al. discloses a method to form built-in stiffener by using a supporting substrate on which the build-up circuitry is formed. In this approach, a peeling promotion layer is applied on the supporting substrate so that the build-up layers can be separated from the supporting substrate after the coreless wiring board is finished. Since the peeling promotion layer, either a thermal setting resin or an oxide film, has the peeling off property when under a heat or light treatment, there exists a high risk of early delamination during dielectric layer coating and curing, this may result in serious yield and reliability concerns.
In view of the various development stages and limitations in currently available coreless substrate for high I/O and high performance semiconductor devices, there is a need for a packaging board that can provide optimize signal integrity, maintain low warping during assembly and operation, and low cost manufacturing.
The present invention provides a method for making a cavity substrate that includes a build-in stiffener and an interconnect substrate with a selected portion of the interconnect substrate exposed from the cavity. The method for making the cavity substrate can include: providing a supporting board that includes a sacrificial carrier, a stiffener and an adhesive, wherein (i) the sacrificial carrier includes a bump and a flange, (ii) the bump is adjacent to and integral with the flange and extends from the flange in a first vertical direction, (iii) the flange extends laterally from the bump in lateral directions orthogonal to the first vertical direction, and (iv) the stiffener is attached to the sacrificial carrier via the adhesive between the stiffener and the flange and between the stiffener and the bump; attaching an interconnect substrate to the supporting board from the first vertical direction using a dielectric layer between the interconnect substrate and the supporting board; removing the bump and a portion of the flange adjacent to the bump to form a cavity and expose the dielectric layer from a closed end of the cavity, wherein the cavity is laterally covered and surrounded by the adhesive and faces in the second vertical direction; and forming one or more via openings in the dielectric layer to expose a selected portion of the interconnect substrate.
The interconnect substrate can include one or more circuitry layers. The circuitry layer can laterally extend on an insulating layer, and two neighboring circuitry layers spaced from one another by an insulating layer can be electrically connected to one another by one or more conductive vias. The insulating layer can extend to peripheral edges of the interconnect substrate, and the conductive vias can extend through the insulating layer to provide electrical connections between the circuitry layers. For instance, the interconnect substrate can include a first circuitry layer, a first insulating layer, one or more first conductive vias and a second circuitry layer. The first insulating layer is disposed between the first circuitry layer and the second circuitry layer and extends to peripheral edges of the interconnect substrate. The first conductive vias extend through the first insulating layer and are adjacent to the first circuitry layer and the second circuitry layer to provide electrical connections between the first circuitry layer and the second circuitry layer. Alternatively, the interconnect substrate can further include additional insulating layer, additional conductive vias, and additional circuitry layers if needed for further signal routing. For instance, the interconnect substrate can further include a second insulating layer, one or more second via openings and a third circuitry layer. The second insulating layer is disposed between the second circuitry layer and the third circuitry layer and extends to peripheral edges of the interconnect substrate. The second conductive vias extend through the second insulating layer and are adjacent to the second circuitry layer and the third circuitry layer to provide electrical connections between the second circuitry layer and the third circuitry layer. The first conductive vias and the second conductive vias can have the same size, and the first circuitry layer, the first insulating layer, the second circuitry layer, the second insulating layer and the third circuitry layer can have flat elongated surfaces that face in the first vertical direction.
The method of making a cavity substrate according to the present invention can further include forming one or more conductive vias in the via openings of the dielectric layer. The conductive vias can extend from the interconnect substrate in the second vertical direction and include an exposed contact surface that faces in the second vertical direction. For instance, the conductive vias can contact and extend from the first circuitry layer of the interconnect substrate in the second vertical and be coplanar with or lower than the dielectric layer in the second vertical direction.
The method of making a cavity substrate according to the present invention can further include providing a plated through-hole that extends through the adhesive and the stiffener to provide an electrical connection between both sides of the cavity substrate. Specifically, the method of making a cavity substrate according to the present invention can further include providing a terminal and a plated through-hole that extends through the adhesive and the stiffener to provide an electrical connection between the terminal and the interconnect substrate.
Providing the plated through-hole can include: forming a through-hole that extends through the adhesive and the stiffener in the vertical directions; and then providing a connecting layer on an inner sidewall of the through-hole.
The plated through-hole in an electrically conductive path between the flange and the interconnect substrate can be provided after attaching the interconnect substrate. For instance, after attaching the interconnect substrate that includes a first circuitry layer, a metal layer, a first insulating layer between the first circuitry layer and the metal layer, and one or more first conductive vias that extend through the first insulating layer, the plated through-hole can be provided by forming a through-hole that extends vertically through the supporting board, the dielectric layer and the interconnect substrate in the vertical directions and then providing a connecting layer on an inner sidewall of the through-hole. The plated through-hole can extend through the flange, the adhesive, the stiffener, the dielectric layer, the first insulating layer and the metal layer, and electrically connect the flange to the metal layer. After providing the plated through-hole, the metal layer can be patterned to form an outer circuitry layer that can be electrically connected to the first circuitry layer through the first conductive vias and electrically connected to the terminal through the plated through-hole. Accordingly, the plated though-hole at a first end can extend to and be electrically connected to the outer circuitry of the interconnect substrate and at a second end can extend to and be electrically connected to the flange. In consideration of process efficiency, the metal layer can be simultaneously patterned during removal of the bump and the portion of the flange adjacent to the bump. Alternatively, the metal layer is patterned after all metal deposition steps are accomplished. For instance, the metal layer can be patterned after the conductive vias are deposited in the via openings of the dielectric layer.
Providing the supporting board can include: providing the sacrificial carrier that includes the bump and the flange; and attaching the stiffener to the sacrificial carrier via the adhesive between the stiffener and the flange and between the stiffener and the bump, including aligning the bump with an aperture of the stiffener.
In accordance with one aspect of the present invention, providing the supporting board and attaching the interconnect substrate can include: providing the sacrificial carrier that includes the bump and the flange; then attaching the stiffener to the sacrificial carrier via the adhesive between the stiffener and the flange and between the stiffener and the bump, including aligning the bump with the aperture of the stiffener; and then laminating the interconnect substrate onto sacrificial carrier at the bump and the stiffener using the dielectric layer from the first vertical direction.
In accordance with another aspect of the present invention, providing the supporting board and attaching the interconnect substrate can include: providing the sacrificial carrier that includes the bump and the flange; then attaching the stiffener to the sacrificial carrier via the adhesive between the stiffener and the flange and between the stiffener and the bump and simultaneously laminating the interconnect substrate onto the sacrificial carrier at the bump and the stiffener using the dielectric layer from the first vertical direction, including aligning the bump with an aperture of the stiffener.
Attaching the stiffener to the sacrificial carrier via the adhesive can include: providing the adhesive that is non-solidified (such as a prepreg with uncured epoxy) between the flange of the sacrificial carrier and the stiffener, including aligning the bump of the sacrificial carrier with an opening of the adhesive and the aperture of the stiffener; then flowing the adhesive into a gap located in the aperture between the bump and the stiffener; and then solidifying the adhesive (such as curing the uncured epoxy).
Attaching the stiffener and simultaneously laminating the interconnect substrate can include: providing the adhesive that is non-solidified and between the stiffener and the flange of the sacrificial carrier and simultaneously providing the dielectric layer between the interconnect substrate and the stiffener and between the interconnect substrate and the bump of the sacrificial carrier, including aligning the bump with an opening of the adhesive and the aperture of the stiffener; then flowing the adhesive into a gap located in the aperture between the bump and the stiffener and compressing the dielectric layer onto the sacrificial carrier at the bump and the stiffener and simultaneously compressing the interconnect substrate onto the dielectric layer; then solidifying the adhesive and the dielectric layer.
Flowing the adhesive into the gap can include: applying heat to melt the adhesive; and moving the sacrificial carrier and the stiffener towards one another, thereby moving the bump in the first vertical direction in the aperture and applying pressure to the molten adhesive between the flange and the stiffener, wherein the pressure forces the molten adhesive to flow in the first vertical direction into the gap located in the aperture between the bump and the stiffener.
Solidifying the adhesive can include applying heat to solidify the molten adhesive, thereby mechanically attaching the stiffener to the bump and the flange.
Removing the bump and the portion of the flange adjacent to the bump can include chemical etching process and can be performed in any step after the dielectric layer covers the bump and the stiffener of the supporting board in the first vertical direction. In the case of making a cavity substrate with a plated through-hole, it is preferable to remove the bump and the portion of the flange adjacent to the bump after providing the plated through-hole.
Providing the terminal can include removing a selected portion of the flange. That is, the terminal can be a remaining portion of the flange and adjacent to the plated through-hole and extend from the adhesive in the second vertical direction. In consideration of process efficiency, the terminal can be simultaneously defined during removal of the bump and the portion of the flange adjacent to the bump. That is, removing the bump and the portion of the flange adjacent to the bump can include simultaneously removing another selected portion of the flange to define the terminal.
Forming the via opening in the dielectric layer can be performed after removing the bump and the portion of the flange adjacent to the bump. The via opening can extend through the dielectric layer and be aligned with and adjacent to a selected portion of the first circuitry layer.
The dielectric layer can be deposited and extend to peripheral edges of the cavity substrate by numerous techniques including film lamination, roll coating, spin coating and spray-on deposition. The via openings can be formed through the dielectric layer by numerous techniques including laser drilling, plasma etching and photolithography. The through-hole can be formed by numerous techniques including mechanical drilling, laser drilling and plasma etching with or without wet etching. The conductive vias and the connecting layer can be deposited by numerous techniques including electroplating, electroless plating, evaporating, sputtering, and their combinations as a single layer or multiple layers. The metal layer can be patterned by numerous techniques including wet etching, electro-chemical etching, laser-assist etching, and their combinations with an etch mask thereon that defines circuitry.
The bump and the flange of the sacrificial carrier can be integral with each other and can be made of any material with good processability and good removability. For instance, the bump and the flange can be a single-piece metal or include a single-piece metal at their interface, and the single-piece metal can be copper, aluminum, nickel, iron, tin or their alloys. Moreover, the bump and the flange can be formed by a mechanical stamping process. For instance, providing the sacrificial carrier with the bump and the flange can include mechanically stamping a metal plate. The sacrificial carrier can further include a stamped cavity in the bump and the stamped cavity in the bump faces in the second vertical direction and is covered by the bump in the first vertical direction. The bump and the cavity in the bump can be a stamped portion of the metal plate and the flange can be an unstamped portion of the metal plate.
The bump can have a larger diameter or dimension in the second vertical direction than in the first vertical direction. For instance, the bump can have a cut-off conical or pyramidal shape in which its diameter or dimension decreases as it extends in the first vertical direction from the flange. Accordingly, as the adhesive extends into the gap between the bump and the stiffener in the first vertical direction, the adhesive can have an increasing thickness where it is adjacent to the bump. The bump can also have a cylindrical shape with a constant diameter. Accordingly, the adhesive can have a constant thickness in the gap between the bump and the stiffener.
The cavity in the bump can have a larger diameter or dimension at its entrance than at its floor. For instance, the stamped cavity can have a cut-off conical or pyramidal shape in which its diameter or dimension increases as it extends in the second vertical direction from its floor to its entrance. Alternatively, the stamped cavity can have a cylindrical shape with a constant diameter. The stamped cavity can also have a circular, square or rectangular periphery at its entrance and its floor. The stamped cavity can also conform to the shape of the bump, extend into the opening and the aperture and extend across most of the bump in the vertical and lateral directions.
The adhesive between the flange and the stiffener can flow into a gap located in the aperture between the bump and the stiffener, as above mentioned. Accordingly, the adhesive can contact the bump, the flange and the stiffener, extend laterally from the bump to peripheral edges of the cavity substrate and have a first thickness (in the vertical directions) where it is adjacent to the flange and a second thickness (in the lateral directions) where it is adjacent to the bump that is different from the first thickness.
The sacrificial carrier may be entirely removed. However, it is preferable to reserve selected portions of the flange as a supporting platform for a heat sink attached thereon. Furthermore, the flange also can be processed into a terminal that is electrically connected to the interconnect substrate through the plated through-hole and can be used for grounding or serve as an electrical contact for the next level assembly or another electronic device.
By the above-mentioned method, the present invention can provide a cavity substrate that includes a cavity, an adhesive, a stiffener, a dielectric layer and an interconnect substrate, wherein (i) the cavity has a closed end in the first vertical direction and an open end in the second vertical direction; (ii) the stiffener includes an aperture, wherein the cavity extends into the aperture; (iii) the adhesive laterally covers and surrounds and conformally coats a sidewall of the cavity, extends laterally from the cavity to peripheral edges of the substrate and covers and contacts the stiffener in the second vertical direction; (iv) the dielectric layer covers the closed end of the cavity and adhesive in the first vertical direction and includes one or more via openings that are aligned with the cavity; and (iv) the interconnect substrate covers the dielectric layer in the first vertical direction and includes a circuitry layer that is adjacent to the via openings.
The stiffener can extend to peripheral edges of the cavity substrate to provide mechanical support for the interconnect substrate and can be made of organic materials such as copper-clad laminate. The stiffener can also be made of inorganic materials such as aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (SiN), silicon (Si), copper (Cu), aluminum (Al), stainless steel, etc. Alternatively, the stiffener can be a single layer structure or a multi-layer structure such as a circuit board or a multi-layer ceramic board or a laminate of a substrate and a conductive layer.
The adhesive can extend to peripheral edges of the cavity substrate and the mechanical rigidity of the cured adhesive also can provide mechanical support for the interconnect substrate. Additionally, the adhesive can cover the stiffener in the second vertical direction and extend into the aperture of the stiffener and conformally coat the sidewall of the cavity. Accordingly, the adhesive can have a first thickness where it is adjacent to the sidewall of the cavity and a second thickness where it covers the stiffener in the second vertical direction that is different from the first thickness. The adhesive can be made of the materials that are at least one selected from the group consisting of epoxy resin, bismaleimide triazine (BT), benzocyclobutene (BCB), Ajinomoto build-up film (ABF), liquid crystal polymer, polyimide, poly(phenylene ether), poly(tetrafluorothylene), aramide and glass fiber.
The cavity substrate provided by the present invention can further include: a terminal that extends beyond the adhesive in the second vertical direction and is spaced from the interconnect substrate by the adhesive, the stiffener and the dielectric layer; and a plated through-hole that extends through the adhesive and the stiffener to provide an electrical connection between the interconnect substrate and the terminal.
The cavity substrate provided by the present invention can further include one or more conductive vias in the via openings of the dielectric layer. The conductive via can contact and extend from the circuitry layer of the interconnect substrate into the via opening in the second vertical direction.
The interconnect substrate can extend from, contact and cover the dielectric layer in the first vertical direction. Furthermore, the interconnect substrate can include one or more interconnect pads that are defined from selected portions of outer circuitry and electrically connected to inner circuitry through conductive vias and extend from an insulating layer in the first vertical direction and include an exposed contact surface that faces in the first vertical direction to provide an electrical contact for the next level assembly or another electronic device such as a semiconductor chip, a plastic package or another semiconductor assembly. Likewise, the terminal can include an exposed contact surface that faces in the second vertical direction as another electrical contact for the next level assembly or another electronic device. As a result, the cavity substrate includes electrical contacts that are electrically connected to one another and located on opposite surfaces that face in opposite vertical directions so that the cavity substrate is stackable.
The present invention also provides a semiconductor assembly in which a semiconductor device can extend into the cavity defined in the adhesive and be electrically connected to the conductive via or the circuitry layer exposed from the cavity using a wide variety of connection media including gold or solder bumps or bonding wires. Optionally, an under-fill can be dispensed within the cavity and a heat sink may be attached on the semiconductor device to enhance thermal performance.
Moreover, the present invention further provides a three-dimensional stacking structure where plural stackable semiconductor assemblies each with a semiconductor device embedded in the cavity are stacked using a wide variety of connection media. For instance, the assemblies can be face-to-back vertically stacked using solder balls between the terminal of the bottom assembly and the interconnect pad of the top assembly.
The semiconductor device can be a packaged or unpackaged semiconductor chip. For instance, the semiconductor device can be a land grid array (LGA) package or wafer level package (WLP) that includes a semiconductor chip or an assembly with chips on an interposer. Alternatively, the semiconductor device can be a semiconductor chip.
The assembly can be a first-level or second-level single-chip or multi-chip device. For instance, the assembly can be a first-level package that contains a single chip or multiple chips. Alternatively, the assembly can be a second-level module that contains a single package or multiple packages, and each package can contain a single chip or multiple chips.
Unless specific descriptions or using the term “then” between steps or steps necessarily occurring in a certain order, the sequence of the above-mentioned steps is not limited to that set forth above and may be changed or reordered according to desired design.
The present invention has numerous advantages. The supporting board which contains a stiffener provides a flat and stable platform for attaching the interconnect substrate and thus make the manufacturing process easy to handle. The bump of the sacrificial carrier which defines a cavity area for device placement can only be separated from the dielectric layer by etching thus ensure a high manufacturing yield without un-predictable peeling or delamination concern. Furthermore, vast options of the built-in stiffener ranging from low coefficient of thermal expansion (CTE) materials like ceramics, to high thermal conductive materials like metal plate, to low cost materials like glass-fiber epoxy provide diversified solutions for various packaging designs. As a result, a semiconductor device can be mounted into the cavity without special alignment tool to achieve low profile and small form-factor requirements. The electrical connection between the semiconductor device and the interconnect substrate can be successfully established through the well-defined conductive vias or the exposed portion of the circuitry layer at the cavity without the troublesome matter that the lamination-induced displacement and warping which often cause the failure of semiconductoor package. The plated through-hole can provide vertical signal routing between the interconnect substrate and the terminal, thereby providing the cavity substrate with stacking capability.
These and other features and advantages of the present invention will be further described and more readily apparent from a review of the detailed description of the preferred embodiments which follows.
The following detailed description of the preferred embodiments of the present invention can best be understood when read in conjunction with the following drawings, in which:
Hereafter, examples will be provided to illustrate the embodiments of the present invention. Other advantages and effects of the invention will become more apparent from the disclosure of the present invention. It should be noted that these accompanying figures are simplified. The quantity, shape and size of components shown in the figures may be modified according to practically conditions, and the arrangement of components may be more complex. Other various aspects also may be practiced or applied in the invention, and various modifications and variations can be made without departing from the spirit of the invention based on various concepts and applications.
Bump 16 is adjacent to and integral with flange 18 and extends from flange 18 in the downward direction. Bump 16 includes bent corners 22 and 24, tapered sidewall 26 and floor 28. Bent corners 22 and 24 are bent by the stamping operation. Bent corner 22 is adjacent to flange 18 and tapered sidewall 26 and bent corner 24 is adjacent to tapered sidewall 26 and floor 28. Tapered sidewall 26 extends outwardly as it extends in the upward direction and floor 28 extends laterally in lateral directions (such as left and right) orthogonal to the upward and downward directions. Thus, bump 16 has a cut-off pyramidal shape (resembling a frustum) in which its diameter decreases as it extends downwardly from flange 18 to floor 28 and increases as it extends upwardly from floor 28 to flange 18. Bump 16 has a height of 300 microns relative to flange 18, a dimension of 10.5 mm by 8.5 mm at flange 18 and a dimension of 10.25 mm by 8.25 mm at floor 28. Furthermore, bump 16 has an irregular thickness due to the stamping operation. For instance, tapered sidewall 26 is thinner than floor 28 since it is elongated by the stamping operation. Bump 16 is shown with a uniform thickness for convenience of illustration.
Flange 18 extends laterally from bump 16 in the lateral directions, is flat and has a thickness of 200 microns.
Stamped cavity 20 faces in the upward direction, extends into bump 16, is covered by bump 16 in the downward direction and has an entrance at flange 18. Stamped cavity 20 also conforms to the shape of bump 16. Thus, stamped cavity 20 has a cut-off pyramidal shape (resembling a frustum) in which its diameter decreases as it extends downwardly from its entrance at flange 18 to floor 28 and increases as it extends upwardly from floor 28 to its entrance at flange 18. Furthermore, stamped cavity 20 extends across most of bump 16 in the vertical and lateral directions and has a depth of 300 microns.
Adhesive 30 can be various dielectric films or prepregs formed from numerous organic or inorganic electrical insulators. For instance, adhesive 30 can initially be a prepreg in which thermosetting epoxy in resin form impregnates a reinforcement and is partially cured to an intermediate stage. The epoxy can be FR-4 although other epoxies such as polyfunctional and bismaleimide triazine (BT) are suitable. For specific applications, cyanate esters, polyimide and PTFE are also suitable. The reinforcement can be E-glass although other reinforcements such as S-glass, D-glass, quartz, kevlar aramid and paper are suitable. The reinforcement can also be woven, non-woven or random microfiber. A filler such as silica (powdered fused quartz) can be added to the prepreg to improve thermal conductivity, thermal shock resistance and thermal expansion matching. Commercially available prepregs such as SPEEDBOARD C prepreg by W.L. Gore & Associates of Eau Claire, Wis. are suitable.
Substrate 34 is illustrated as a single layer dielectric structure. Stiffener 33 can also be an electrical interconnect such as a multi-layer printed circuit board or a multi-layer ceramic board. Accordingly, stiffener 33 can include embedded circuitry.
In
Bump 16 is inserted into but not through aperture 40 without contacting stiffener 33 and is aligned with and centrally located within aperture 40. As a result, gap 42 is located in aperture 40 between bump 16 and stiffener 33. Gap 42 laterally surrounds bump 16 and is laterally surrounded by stiffener 33. In addition, opening 32 and aperture 40 are precisely aligned with one another and have the same dimension.
At this stage, stiffener 33 is mounted on and contacts and extends above adhesive 30. Bump 16 extends through opening 32 into aperture 40, is 30 microns below the top surface of conductive layer 36 and is exposed through aperture 40 in the upward direction. Adhesive 30 contacts and is sandwiched between flange 18 and substrate 34, contacts substrate 34 but is spaced from conductive layer 36 and remains a non-solidified prepreg with B-stage uncured epoxy, and gap 42 is filled with air.
For instance, flange 18 and conductive layer 36 can be disposed between top and bottom platens (not shown) of a press. In addition, a top cull plate and top buffer paper (not shown) can be sandwiched between conductive layer 36 and the top platen, and a bottom cull plate and bottom buffer paper (not shown) can be sandwiched between flange 18 and the bottom platen. The stack includes the top platen, top cull plate, top buffer paper, substrate 34 and conductive layer 36, adhesive 30, flange 18, bottom buffer paper, bottom cull plate and bottom platen in descending order. Furthermore, the stack may be positioned on the bottom platen by tooling pins (not shown) that extend upward from the bottom platen through registration holes (not shown) in flange 18.
The platens are heated and move towards one another, thereby applying heat and pressure to adhesive 30. The cull plates disperse the heat from the platens so that it is more uniformly applied to flange 18 and stiffener 33 and thus adhesive 30, and the buffer papers disperse the pressure from the platens so that it is more uniformly applied to flange 18 and stiffener 33 and thus adhesive 30. Initially, stiffener 33 contacts and presses down on adhesive 30. As the platen motion and heat continue, adhesive 30 between flange 18 and stiffener 33 is compressed, melted and flows into and upward in gap 42 and across substrate 34 to conductive layer 36. For instance, the uncured epoxy is melted by the heat and the molten uncured epoxy is squeezed by the pressure into gap 42, however the reinforcement and the filler remain between flange 18 and stiffener 33. Adhesive 30 elevates more rapidly than bump 16 in aperture 40 and fills gap 42. Adhesive 30 also rises slightly above aperture 40 and overflows onto the top surfaces of bump 16 and conductive layer 36 before the platen motion stops. This may occur due to the prepreg being slightly thicker than necessary. As a result, adhesive 30 creates a thin coating on the top surfaces of bump 16 and conductive layer 36. The platen motion is eventually blocked by bump 16 and the platens become stationary but continue to apply heat to adhesive 30.
The upward flow of adhesive 30 in gap 42 is shown by the thick upward arrows, the upward motion of bump 16 and flange 18 relative to stiffener 33 is shown by the thin upward arrows, and the downward motion of stiffener 33 relative to bump 16 and flange 18 is shown by the thin downward arrows.
For instance, the platens continue to clamp bump 16 and flange 18 and apply heat after the platen motion stops, thereby converting the B-stage molten uncured epoxy into C-stage cured or hardened epoxy. Thus, the epoxy is cured in a manner similar to conventional multi-layer lamination. After the epoxy is cured, the platens move away from one another and the structure is released from the press.
Adhesive 30 as solidified provides a secure robust mechanical bond between bump 16 and stiffener 33 and between flange 18 and stiffener 33. Adhesive 30 can withstand normal operating pressure without distortion or damage and is only temporarily distorted under unusually high pressure. Furthermore, adhesive 30 can absorb thermal expansion mismatch between bump 16 and stiffener 33 and between flange 18 and stiffener 33.
At this stage, bump 16 and conductive layer 36 are essentially coplanar with one another and adhesive 30 and conductive layer 36 extend to a top surface that faces in the upward direction. For instance, adhesive 30 between flange 18 and stiffener 33 has a thickness of 120 microns which is 30 microns less than its initial thickness of 150 microns, bump 16 ascends 30 microns in aperture 40 and stiffener 33 descends 30 microns relative to bump 16. The 300 micron height of bump 16 is essentially the same as the combined height of conductive layer 36 (30 microns), substrate 34 (150 microns) and the underlying adhesive 30 (120 microns). Furthermore, bump 16 continues to be centrally located in opening 32 and aperture 40 and spaced from stiffener 33 and adhesive 30 fills the space between flange 18 and stiffener 33 and fills gap 42. Adhesive 30 extends across stiffener 33 in gap 42. That is, adhesive 30 in gap 42 extends in the upward and downward directions across the thickness of stiffener 33 at the outer sidewall of gap 42. Adhesive 30 also includes a thin top portion above gap 42 that contacts the top surfaces of bump 16 and conductive layer 36 and extends above bump 16 by 10 microns.
The grinding removes a 20 micron thick upper portion of adhesive 30, a 10 micron thick upper portion of bump 16 and a 10 micron thick upper portion of conductive layer 36. The decreased thickness does not appreciably affect bump 16 or adhesive 30. However, it substantially reduces the thickness of conductive layer 36 from 30 microns to 20 microns. After the grinding, bump 16, adhesive 30 and conductive layer 36 are coplanar with one another at a smoothed lapped lateral top surface that is above substrate 34 and faces in the upward direction.
At this stage, as shown in
Stamped cavity 20 faces in the downward direction, extends into remains centrally located within bump 16, opening 32 and aperture 40 and is covered by bump 16 in the upward direction. Stamped cavity 20 conforms to the shape of bump 16, extends across most of bump 16 in the vertical and lateral directions and retains its cut-off pyramidal shape in which its dimension decreases as it extends upwardly from its entrance at flange 18.
Flange 18 extends laterally from bump 16, extends below adhesive 30, stiffener 33, opening 32 and aperture 40, contacts adhesive 30 and is spaced from stiffener 33.
Adhesive 30 contacts and is sandwiched between and fills the space between bump 16 and stiffener 33 in gap 42 and contacts stiffener 33 and flange 18 outside gap 42. Adhesive 30 covers and surrounds tapered sidewall 26 of bump 16 in the lateral directions, extends laterally from bump 16 to peripheral edges of the assembly and is solidified. Accordingly, adhesive 30 has first thickness T1 where it is adjacent to flange 18 and second thickness T2 where it is adjacent to bump 16 that is different from first thickness T1. That is, distance D1 in the vertical directions between flange 18 and stiffener 33 is different from distance D2 in the lateral directions between bump 16 and stiffener 33. Furthermore, as adhesive 30 extends away from flange 18 into gap 42 between bump 16 and stiffener 33, adhesive 30 can have an increasing thickness where it is adjacent to bump 16 owing to that bump 16 has an increasing dimension as it extends towards flange 18.
Supporting board 101 with multiple bumps can be accomplished by stamping sacrificial carrier 10 to include additional bumps 16, adjusting adhesive 30 to include additional openings 32 and adjusting stiffener 33 to include additional apertures 40.
Subsequently, as shown in
As shown in
Referring now to
For instance, connecting layer 62 is deposited by first dipping the structure in an activator solution to render through-hole 401 catalytic to electroless copper, then a thin copper layer is electrolessly plated to serve as the seeding layer before a second copper layer is electroplated on the seeding layer to a desirable thickness.
Also shown in
Bump 16, flange 18, metal layer 261, plated layer 60 and connecting layer 62 are shown as a single layer for convenience of illustration. The boundary (shown in phantom) between the metal layers may be difficult or impossible to detect since copper is plated on copper. However, the boundaries between the metal layers and adhesive 30, substrate 34, dielectric layer 211 and first insulating layer 251 are clear.
At this stage, as shown in
In this illustration, cavity substrate 100 includes adhesive 30, stiffener 33, terminal 182, dielectric layer 211, interconnect substrate 201 and plated through-hole 402. However, in some embodiments, terminal 182 and plated through-hole 402 may be omitted according to desired design. Furthermore, supporting board 101 may include multiple cavities 31 by applying sacrificial carrier 10 with multiple bumps 16 and thus defining multiple cavities 31 in adhesive 30.
Interconnect substrate 201 includes first circuitry layer 231, first insulating layer 251, first conductive vias 263 and second circuitry layer 271. First circuitry layer 231 and second circuitry layer 271 can provide horizontal signal routing in both the X and Y directions, and first conductive vias 263 can provide vertical (top to bottom) routing. First circuitry layer 231 extends from first insulating layer 251 in the upward direction, extends laterally on first insulating layer 251 and is covered by dielectric layer 211 in the upward direction. Selected portions of first circuitry layer 231 are exposed from cavity 31 in the upward direction and can serve as electrical contacts for a semiconductor device embedded in cavity 31 and provide an electrical connection between the semiconductor device and interconnect substrate 201. Second circuitry layer 271 extends from first insulating layer 251 in the downward direction and extends laterally on first insulating layer 251. First circuitry layer 231 and second circuitry layer 271 can be electrically connected to one another through first conductive vias 263 that extend through first insulating layer 251 and are adjacent to first circuitry layer 231 and second circuitry layer 271.
Adhesive 30 is solidified, laterally covers and surrounds and conformally coats a sidewall of cavity 31, extends laterally from cavity 31 to peripheral edges of cavity substrate 100, is sandwiched between terminal 182 and stiffener 33 outside gap 42, covers and contacts stiffener 33 in the upward direction, covers and contacts terminal 182 in the downward direction, and contacts connecting layer 62 in the lateral direction. Adhesive 30 has a first thickness where it is adjacent to the sidewall of cavity 31 and a second thickness where it covers stiffener 33 in the upward direction that is different from the first thickness. The mechanical rigidity of cured adhesive 30 and stiffener 33 can provide mechanical support for interconnect substrate 201.
Terminal 182 extends from adhesive 30 in the upward direction, is spaced from interconnect substrate 201 and is adjacent to and integral with plated through-hole 402. Terminal 182 has a combined thickness of flange 18 and plated layer 60, and can be used for grounding or/and supporting a heat sink attached on an embedded semiconductor device in cavity 31 or serve as an electrical contact for another semiconductor device or assembly.
Plated through-hole 402 is spaced from conductive layer 36 and first circuitry layer 231 and extends vertically from terminal 182 to second circuitry layer 271 through first insulating layer 251, dielectric layer 211, substrate 34 and adhesive 30 in an electrically conductive path between terminal 182 and second circuitry layer 271. Thus, plated through-hole 402 extends from terminal 182 to the outer conductive layer of interconnect substrate 201 and is spaced from the inner conductive layer of interconnect substrate 201.
Interconnect substrate 201 may include additional interconnect layers (i.e. a second insulating layer, second conductive vias, a third circuitry layer and so on), if desired.
Cavity substrate 100 can accommodate multiple semiconductor devices rather than one with a single cavity or multiple cavities. Thus, multiple semiconductor devices can be mounted into a single cavity or separate semiconductor devices can be mounted into separate cavities. Accordingly, interconnect substrate 201 may include additional conductive traces for additional devices.
For purposes of brevity, any description in Embodiment 1 is incorporated herein insofar as the same is applicable, and the same description need not be repeated.
The upward motion of sacrificial carrier 10 relative to interconnect substrate 201 is shown by the thin upward arrows, and the downward motion of interconnect substrate 201 relative to sacrificial carrier 10 is shown by the thin downward arrows.
After adhesive 30 fills up gap 42 and dielectric layer 211 and interconnect substrate 201 are laminated, adhesive 30 and dielectric layer 211 are solidified. Accordingly, adhesive 30 and dielectric layer 211 as solidified respectively provide secure robust mechanical bonds between sacrificial carrier 10 and stiffener 33, between interconnect substrate 201 and sacrificial carrier 10, and between interconnect substrate 201 and stiffener 33.
At this stage, as shown in
Bump 16, flange 18, metal layer 261, plated layer 60 and connecting layer 62 are shown as a single layer for convenience of illustration. The boundary (shown in phantom) between the metal layers may be difficult or impossible to detect since copper is plated on copper. However, the boundary between metal layers and adhesive 30, stiffener 33, dielectric layer 211 and first insulating layer 251 are clear.
At this stage, as shown in
At this stage, as shown in
For purposes of brevity, any description in Embodiments 1 and 2 is incorporated herein insofar as the same is applicable, and the same description need not be repeated.
At this stage, as shown in
Referring now to
First and second conductive traces 291, 292 can be deposited as a conductive layer by numerous techniques including electrolytic plating, electroless plating, sputtering, and their combinations and then patterned by numerous techniques including wet etching, electro-chemical etching, laser-assist etching, and their combinations with an etch mask (not shown) thereon that defines first and conductive traces 291, 292.
Also shown in
At this stage, as shown in
The cavity substrates, stackable semiconductor assemblies and 3D stacking structures described above are merely exemplary. Numerous other embodiments are contemplated. In addition, the embodiments described above can be mixed-and-matched with one another and with other embodiments depending on design and reliability considerations. For instance, the stiffener can include ceramic material or epoxy-based laminate, and can have embedded single-level conductive traces or multi-level conductive traces. The supporting board can include multiple bumps to define multiple cavities in the adhesive. Accordingly, the cavity substrate can include multiple cavities arranged in an array for multiple semiconductor devices, and the interconnect substrate can includes additional circuitries to accommodate additional semiconductor devices.
The semiconductor device can share or not share the cavity with other semiconductor devices. For instance, a single semiconductor device can be mounted into the built-in cavity. Alternatively, numerous semiconductor devices can be mounted into the built-in cavity. For instance, four small chips in a 2×2 array can be placed in the built-in cavity and additional conductive vias can be provided for additional chips. This may be more cost effective than providing a miniature cavity for each chip.
The semiconductor device can be a packaged or unpackaged chip. Furthermore, the semiconductor device can be a bare chip, LGA, or QFN, etc. The semiconductor device can be mechanically and electrically connected to the cavity substrate using a wide variety of connection media including solder. The built-in cavity can be customized for the semiconductor device embedded therein. For instance, the cavity can have a square or rectangular shape at its bottom with the same or similar topography as the semiconductor device.
The supporting board can provide a robust mechanical support for the interconnect substrate, and the interconnect substrate provides shorten signal routing so that signal loss and distortion can be reduced under accelerated operation of the semiconductor device.
The term “adjacent” refers to elements that are integral (single-piece) or in contact (not spaced or separated from) with one another. For instance, the bump is adjacent to the flange but not the stiffener.
The term “overlap” refers to above and extending within a periphery of an underlying element. Overlap includes extending inside and outside the periphery or residing within the periphery. For instance, in the cavity-up position, the flange overlaps the stiffener since an imaginary vertical line intersects the flange and the stiffener, regardless of whether another element such as the adhesive is between the flange and the stiffener and is intersected by the line, and regardless of whether another imaginary vertical line intersects the flange but not the stiffener (within the aperture of the stiffener). Likewise, the adhesive overlaps the stiffener, the flange overlaps the adhesive and the stiffener is overlapped by the adhesive. Moreover, overlap is synonymous with over and overlapped by is synonymous with under or beneath.
The term “contact” refers to direct contact. For instance, the stiffener contacts the adhesive but does not contact the bump.
The term “cover” refers to incomplete and complete coverage in a vertical and/or lateral direction. For instance, in the cavity-up position, the adhesive covers the stiffener but does not cover the bump in the upward direction.
The term “layer” refers to patterned and un-patterned layers. For instance, the conductive layer can be an un-patterned blanket sheet on the substrate when the stiffener including the conductive layer and the substrate is mounted on the adhesive. Furthermore, a layer can include stacked layers.
The terms “opening” and “aperture” and “hole” refer to a through hole and are synonymous. For instance, in the cavity-down position, the bump is exposed by the adhesive in the upward direction when it is inserted into the opening in the adhesive. Likewise, the bump is exposed by the stiffener in the upward direction when it is inserted into the aperture in the stiffener.
The term “inserted” refers to relative motion between elements. For instance, the bump is inserted into the aperture regardless of whether the flange is stationary and the stiffener moves towards the flange, the stiffener is stationary and the flange moves towards the stiffener or the flange and the stiffener both approach the other. Furthermore, the bump is inserted (or extends) into the aperture regardless of whether it goes through (enters and exits) or does not go through (enters without exiting) the aperture.
The phrase “move towards one another” also refers to relative motion between elements. For instance, the flange and the stiffener move towards one another regardless of whether the flange is stationary and the stiffener moves towards the flange, the stiffener is stationary and the flange moves towards the stiffener or the flange and the stiffener both approach the other.
The phrase “aligned with” refers to relative position between elements. For instance, the bump is aligned with the aperture when the adhesive is mounted on the flange, the stiffener is mounted on the adhesive, the bump is inserted into and aligned with the opening and the aperture is aligned with the opening regardless of whether the bump is inserted into the aperture or is below and spaced from the aperture.
The phrases “mounted on”, “attached onto”, “attaching . . . onto”, “laminated onto” and “laminating . . . onto” include contact and non-contact with a single or multiple support element(s). For instance, the heat sink can be mounted on the semiconductor device regardless of whether it contacts the semiconductor device or is separated from the semiconductor device by an adhesive.
The phrase “adhesive . . . in the gap” refers to the adhesive in the gap. For instance, adhesive that extends across the stiffener in the gap refers to the adhesive in the gap that extends across the stiffener. Likewise, adhesive that contacts and is sandwiched between the bump and the stiffener in the gap refers to the adhesive in the gap that contacts and is sandwiched between the bump at the inner sidewall of the gap and the stiffener at the outer sidewall of the gap.
The phrase “electrical connection” or “electrically connects” or “electrically connected” refers to direct and indirect electrical connection. For instance, the plated through-hole provides an electrical connection for the first circuitry layer regardless of whether it is adjacent to the first circuitry layer or electrically connected to the first circuitry layer by the second circuitry layer.
The term “above” refers to upward extension and includes adjacent and non-adjacent elements as well as overlapping and non-overlapping elements. For instance, in the cavity-down position, the bump extends above, is adjacent to and protrudes from the flange.
The term “below” refers to downward extension and includes adjacent and non-adjacent elements as well as overlapping and non-overlapping elements. For instance, in the cavity-up position, the bump extends below, is adjacent to and protrudes from flange in the downward direction. Likewise, the bump extends below the stiffener even though it is not adjacent to or overlapped by the stiffener.
The “first vertical direction” and “second vertical direction” do not depend on the orientation of the cavity substrate (or the supporting board), as will be readily apparent to those skilled in the art. For instance, the bump extends vertically beyond the stiffener in the second vertical direction and vertically beyond the flange in the first vertical direction regardless of whether the supporting board is inverted. Likewise, the flange extends “laterally” from the bump in a lateral plane regardless of whether the supporting board is inverted, rotated or slanted. Thus, the first and second vertical directions are opposite one another and orthogonal to the lateral directions, and laterally aligned elements are coplanar with one another at a lateral plane orthogonal to the first and second vertical directions. Furthermore, the first vertical direction is the downward direction and the second vertical direction is the upward direction in the cavity-up position, and the first vertical direction is the upward direction and the second vertical direction is the downward direction in the cavity-down position.
The cavity substrate and the semiconductor assembly using the same according to the present invention have numerous advantages. The cavity substrate and the semiconductor assembly are reliable, inexpensive and well-suited for high volume manufacture. A heat sink can be attached on the device mounted into the built-in cavity of the cavity substrate to facilitate heat dissipation. Therefore, the cavity substrate is especially well-suited for high power semiconductor devices and large semiconductor chips as well as multiple semiconductor devices such as small semiconductor chips in arrays which generate considerable heat and require excellent heat dissipation in order to operate effectively and reliably.
The manufacturing process is highly versatile and permits a wide variety of mature electrical and mechanical connection technologies to be used in a unique and improved manner. The manufacturing process can also be performed without expensive tooling. As a result, the manufacturing process significantly enhances throughput, yield, performance and cost effectiveness compared to conventional packaging techniques.
The embodiments described herein are exemplary and may simplify or omit elements or steps well-known to those skilled in the art to prevent obscuring the present invention. Likewise, the drawings may omit duplicative or unnecessary elements and reference labels to improve clarity.
Various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. For instance, the materials, dimensions, shapes, sizes, steps and arrangement of steps described above are merely exemplary. Such changes, modifications and equivalents may be made without departing from the spirit and scope of the present invention as defined in the appended claims.
This application is a continuation-in-part of U.S. application Ser. No. 13/197,163 filed Aug. 3, 2011, a continuation-in-part of U.S. application Ser. No. 13/267,946 filed Oct. 7, 2011, a continuation-in-part of U.S. application Ser. No. 13/299,472 filed Nov. 18, 2011, a continuation-in-part of U.S. application Ser. No. 13/299,495 filed Nov. 18, 2011, a continuation-in-part of U.S. application Ser. No. 13/532,941 filed Jun. 26, 2012 and a continuation-in-part of U.S. application Ser. No. 13/738,220 filed Jan. 10, 2013, each of which is incorporated by reference. This application also claims the benefit of filing date of U.S. Provisional Application Ser. No. 61/635,902 filed Apr. 20, 2012. U.S. application Ser. No. 13/197,163 filed Aug. 3, 2011, U.S. application Ser. No. 13/267,946 filed Oct. 7, 2011, U.S. application Ser. No. 13/299,472 filed Nov. 18, 2011 and U.S. application Ser. No. 13/299,495 filed Nov. 18, 2011 all claim the benefit of filing date of U.S. Provisional Application Ser. No. 61/415,862 filed Nov. 22, 2010. U.S. application Ser. No. 13/532,941 filed Jun. 26, 2012 and U.S. application Ser. No. 13/738,220 filed Jan. 10, 2013 claim the benefit of filing date of U.S. Provisional Application Ser. No. 61/635,902 filed Apr. 20, 2012. U.S. application Ser. No. 13/299,472 filed Nov. 18, 2011 is a continuation-in-part of U.S. application Ser. No. 13/197,163 filed Aug. 3, 2011. U.S. application Ser. No. 13/299,495 filed Nov. 18, 2011 is a continuation-in-part of U.S. application Ser. No. 13/267,946 filed Oct. 7, 2011. U.S. application Ser. No. 13/532,941 filed Jun. 26, 2012 is a continuation-in-part of U.S. application Ser. No. 13/197,163 filed Aug. 3, 2011, a continuation-in-part of U.S. application Ser. No. 13/267,946 filed Oct. 7, 2011, a continuation-in-part of U.S. application Ser. No. 13/299,472 filed Nov. 18, 2011 and a continuation-in-part of U.S. application Ser. No. 13/299,495 filed Nov. 18, 2011. U.S. application Ser. No. 13/738,220 filed Jan. 10, 2013 is a continuation-in-part of U.S. application Ser. No. 13/532,941 filed Jun. 26, 2012.
