This invention relates to a chip package, especially to a flip-chip package and the fabrication thereof.
As the developments of the semiconductor fabrication toward to the nanometer-scale, there are more standard cells formed on the chip having the same area. Then, the chip provides more and more powerful functions to satisfy the different needs. At the same time, the contacts or the die pads on the chip are also developed toward to high count and high density to transmit the various signals.
In respect to the interconnection between the chip and the substrate, the bonding process is necessary to electrically and mechanically connect with the die pads on the chip and the corresponding pads on the substrate. For example, the common bonding technologies are: the wire bonding technique, the tape automatic bonding (TAB) technique, and the flip-chip technique. The flip-chip technique is the most popular one in recent days because it provides a higher contact count and a dense contact arrangement. The wire bonding technique and the TAB technique are only used the around area in the active surface of the chip. However, the flip-chip technique would use the most area in the active surface of the chip to achieve a higher contact count. Besides, the flip-chip package provides a better electrical performance because the signal transmission path between the chip and the substrate is shortened in the flip-chip package.
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In order to provide an easier assembly of the chip and the substrate and to enhance the mechanical stress and the reliability of the chip, the chip 10 is disposed on a chip carrier 20 and then is packaged in the molding material. Please referring to
Referring to
The underfilling process is executed after bonding the chip 10 and the chip carrier 20. In order to prevent the voids formed in the space between the chip 10 and the chip carrier 20, the chip charier 20 is heated at 60˜80° C. to enhance the capillarity. Then, the underfill material 30 is baking about 150° C. in the curing process. Thus, the fabrication time and cost are increased in the underfilling process and curing process. In addition, the dimensions of the bumps, the pitches of the bumps, and the arrangements of the bumps will affect the capillarity of the underfill material. In other words, the arrangement of the bumps is limited to prevent the voids generation and to enhance the reliability of the package. Besides, the bumping process to dispose the bumps on the die pads will increase the risk to damage the chips. The fabricating cost is increased because the loss in the bumping process.
In the foregoing descriptions, it is desirable to provide a flip-chip package with a lower cost and a higher reliability and to provide the fabrication thereof.
In accordance with the background of the above-mentioned invention, the present invention discloses a flip-chip package to connect with the chip and the chip carrier through an interposer and the fabrication thereof.
In the embodiments according to the present invention, there is an interposer disposed between the chip and the chip carrier. The interposer comprises an insulation layer for mechanical support, a first adhesive layer, a second adhesive layer, and a plurality of conductive elements. The first adhesive layer is disposed on a first surface of the insulation layer; likewise the second adhesive layer is disposed on a second surface of the insulation layer. The conductive elements pass through the insulation layer, the first adhesive layer, and the second adhesive layer. And the dimensions and the arrangement of the conductive elements are corresponding to the die pads of the chip.
The flip-chip package with the interposer comprises a chip, an interposer, and a chip carrier. A plurality of die pads disposes on an active surface of the chip. For the connections between the chip and the chip carrier, the interposer having a plurality of conductive elements corresponding to the die pads, and the chip carrier also having a plurality of bump pads corresponding to the die pads. One die pad electrically connects to the corresponding bump pad through one conductive element. The interposer further comprises an insulation layer for mechanical support and two adhesive layers to bond the chip and to bond the chip carrier, respectively. The fabrication of the flip-chip package through the interposer enhances the mechanical strength and the reliability of the packages.
The fabrication of the flip-chip package comprises providing a chip having a plurality of die pads, providing a chip carrier having a plurality of bump pads, providing an interposer having a plurality of conductive elements, stacking and aligning the chip, the interposer and the chip carrier, and bonding the chip, the interposer and the chip carrier.
Other aspects, features and advantages of the invention will become apparent form the following detailed description, taken in conjunction with the accompanying drawing.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
a shows a cross-sectional view of a chip according to the prior art.
b shows a cross-sectional view of the flip-chip package in the bonding process according to the prior art.
c shows a cross-sectional view of the finished flip-chip package according to the prior art.
a shows a cross-sectional view of the separated elements according to the present invention.
b shows a cross-sectional view of the finished flip-chip package according to the present invention.
The present invention provides a flip-chip package having an interposer for the interconnection between the chip and the chip carrier and provides a fabrication thereof.
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In order to electrically connect with the chip 10 and the chip carrier 20, the embodiment further comprises an interposer 40 disposed between the chip 10 and the chip carrier 20. The interposer 40 comprises an insulation layer 41, a first adhesive layer 42, a second adhesive layer 43, and a plurality of conductive elements 44. The insulation layer 41 is made of a dielectric material for the insulation between the chip 10 and the chip carrier 20 and for the mechanical support of the interposer 40. In addition, the coefficient of thermal expansion (CTE) of the insulation layer 41 is between the CTE of the chip 10 and the CTE of the chip carrier 20. The first adhesive layer 42 is disposed on a first surface of the insulation layer 41, and the second adhesive layer is disposed on a second surface of the insulation layer 41 which is opposite to the first surface. Those adhesive layers are made of polymer, inorganic polymeric composite material, or organic polymeric composite material, such as epoxy resin for example. Those adhesive layers enhance the bonding strength between the chip 10 and the interposer 40 and the bonding strength between the chip carrier 20 and the interposer 40 because these adhesive layers distribute the thermal stress result from the different coefficients of thermal expansion in the chip 10, the chip carrier 20, and the interposer 40. These adhesive layers also provide the protection against moisture and the chemical reaction to reduce the failures in the joints between the chip 10 and the chip carrier 20. The dimensions, the count and the arrangement of the conductive elements 44 depend on those of the die pads 11. One end of each conductive element 44 electrically connects to one die pad 11, and the other end of the conductive element 44 electrically connects to one bump pad 21. In other words, the chip 10 and the chip carrier 20 are electrically connected through the conductive elements 44. For example, the conductive elements 44 is a solder, a metallic material with two solder disposed on two respective ends of the metallic material, or a metallic material with two conductive glues disposed on two respective ends of the metallic material. The solder is the alloy selected from Sn/Pb, Sn/Ag/Cu, Sn/Ag, Sn/Ag/Bi, or Sn/In. The conductive glues have a plurality of conductive particles made of Cu, Au, Ag, Ni or Al. The metallic material is one of Cu, Au, Ag, Ni, and Al, or the conductive glues.
b illustrates to stack and align the chip 10, the interposer 40, and the chip carrier 20, such that each conductive element 44 is in contact with one die pad 11 and one bump pad 21. The width of the interposer 40 is not less than the width of the chip 10 to enhance the bonds between the chip 10 and the interposer 40 and to reduce the cracks occurred at the boundary of the interposer 40. The conductive elements 44 stand out the first adhesive layer 42 and stand out the second adhesive layer 43. Please note that two protruded parts of the conductive elements 44 must match to the height of the passivation layer 12 and match to the height of the solder mask layer 22, respectively. Thus, the first adhesive layer 42 and the chip 10 are laminated without voids; likewise the second adhesive layer 43 and the chip carrier 20 are laminated without voids. In other words, the height of the conductive element 44 is not less than the height of the interposer 40. After heating and pressing on the lamination consist of the chip 10, the interposer 40, and the chip carrier 20, the electrical connection between the chip 10 and the chip carrier 20 is achieved. For example, the conductive element 44 and the die pad 11 are soldered together, and the conductive element 44 and the bump pad 21 are also soldered together in the heating and pressing process. In order to enhance the bonding between the chip 10 and the interposer 40 and the bonding between the chip carrier 20 and the interposer 40, the adhesive layers are polymerized in the curing process by heating the package.
In the foregoing embodiment, the fabrication of the flip-chip package comprises: providing the foregoing chip 10, the foregoing interposer 40, and the foregoing chip carrier 20, stacking and aligning the chip 10, the interposer 40, and the chip carrier 20, and bonding the chip 10, the interposer 40, and the chip carrier 20. The chip 10 has a plurality of die pads 11 as illustrated in foregoing descriptions. In addition, the interposer 40 has a plurality of conductive elements 44, and the chip carrier 20 has a plurality of bump pads 21. Each die pad 11 electrically connects to one bump pad 21 through one conductive element 44 after the bonding process.
The underfilling process is not necessary in the preferred embodiment, thus the cost, the process time, and the failures result from the underfilling process is reduced in the embodiment. Furthermore, the embodiment also keeps away from disposing the bumps on the chip 10. It reduces the risk of damaging the chip 10 in the bumping process and reduces the fabrication cost. In addition, the limitation on the bump arrangement and the limitation on the bump dimension are not necessary because the embodiment is without the underfilling process. In other words, the arrangement of the die pad 11 is more flexible and more efficient to provide the chip with larger count and higher density in contacts.
Please referring to
For a stronger mechanical strength in the joints and an easier soldering process, other media could further disposed between the chip 10 and the interposer 40 and between the chip carrier 20 and the interposer 40. Referring to
Other embodiments of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. Please referring to
According to the above, the present invention has at least the following advantages:
1. Providing a flip-chip package without the bumping process and the fabrication thereof. Time and the risk in chip damage result from the bumping process is reduced, thus the fabricating cost is reduced.
2. Providing a flip-chip package without the underfilling and the fabrication thereof. It further reduces the cost and improves the reliability of the package.
3. Enhancing the reliability of the package because of the well protections on the joints and the tight matches between the chip and the interposer and between the interposer and the chip carrier.
4. Providing a flip-chip package having a higher contact count, a higher contact density and a more flexible contact arrangement.
Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be mode therein without departing from the spirit of the invention and within the scope and claims be constructed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.