Patent Application
20240014628
The present invention relates to a method of manufacturing a package comprising an optoelectronic device, in particular an injection molded circuit carrier, MID. The invention further relates to an optoelectronic device.
In some applications involving lasers, they are packaged, with a lens or other optical element provided to focus the beam. In addition to beam shaping, the optical element may also perform some protective or safeguarding function, ensuring that laser radiation does not inadvertently enter a person's eye.
For this purpose, a so-called interlock circuit is used, i.e. a conductor loop is arranged between the optical element and the package or the optical element and the laser. If the optical element or the package is damaged, the conductor loop is interrupted and the optoelectronic element is switched off.
In the manufacture of such packages, the conductor loop and MLA (optically active structure) are located on opposite surfaces for technical reasons, which limits the design options. As a result, it is currently necessary to glue over the conductor loop. In the past, however, problems arose due to thermomechanical stress between the components to be bonded (cap <->conductive adhesive+non-conductive adhesive <->MLA) in addition to excessive scrap. The punctual conductive bonding and thus interrupted structural bonding do not allow sufficient bonding of the components to be bonded. This can lead to thermally induced damage and thus failure of the entire package. Thus, there is a need to disclose a method of manufacturing a package, in particular an injection molded circuit carrier, MID, in which a thermal stress is reduced during an operation.
The inventors have recognized that with suitable combinations of different manufacturing techniques, thermally induced displacement of the optical element relative to the cap is reduced. Separation of the lens from the cap becomes less likely. This can be aided by the use of mechanical anchors. One aspect of this is to use the manufacturing process to provide the conductor loop and MLA (optically active structure) on the same side of the optical element. This eliminates the need to bond over the conductor loop, reducing shear or other thermally induced forces on the joint.
In one aspect, a method of manufacturing a package, in particular an injection molded circuit carrier, MID, is proposed. Thereby, at least one injection molded cover plate forming a cavity is provided having a cover area and a perimeter defining the cover area, wherein the cover area comprises an opening. The cover plate thus forms an injection molded part. A first conductive trace and a second conductive trace are then formed on the cover plate, each of the first and second conductive traces comprising a first portion on a top edge of the surround, a second portion on a side surface of the surround, and a third portion on the cover area. Next, an optical element is formed in the opening of the cover area such that the optical element is intimately connected to the cover area. A loop-shaped interlock circuit is then applied to the optical element in an edge portion between the opening and the cover area, wherein one end of the loop-shaped interlock circuit is connected to each of the first and second conductive paths. Thus, the loop-shaped interlock circuit is located on the optical element near the edge of the cover area. In the case of a corresponding optical element which terminates planarly with the edge of the cover area, the loop is thus also arranged planarly on the optical element and the cover area or the conductor track.
In the process, an optoelectronic component can also be introduced into the cavity. This can be, for example, an optoelectronic component for ToF applications (time of flight) with a VCSEL emitter and integrated IC driver. The optoelectronic component can also include an emitter (LED, laser), a detector (e.g. photodiode), a sensor and passive components such as capacitors or ESD and ICs. Combinations of such elements are also possible.
In one aspect, the aperture has a step in the cover area, wherein the optical element extends onto the step and the loop-shaped interlock circuit is disposed over the step. The step is also referred to as a perimeter. As a result, an adhesive can be applied to the step to allow an optical element to fit snugly in the opening. In addition, the step in the opening provides an additional support surface for the optical element, e.g. in a subsequent molding process, thus reducing the intimate connection and thus the risk of detachment. The opening can be square or rectangular in shape, and is optionally arranged off-center in the cover plate.
In a further aspect, the opening comprises a particularly semicircular bulge on one side, particularly between the first and second conductive tracks. The bulge can accommodate excess adhesive or excess material of the optical element. This allows manufacturing tolerances to be compensated.
Various methods may be used to create the first and second conductive paths. In one aspect, a laser-activatable metal compound is provided as a plastic additive that is present at the locations or regions of the cover plate that will later form the conductive traces. In one aspect, the cover plate may be immediately fully molded with a plastic doped with the laser-activatable metal compound. A suitable material is a solder-stable thermoplastic based on PPA, LCD or PPS. Then, areas of the first, second and third sections of each trace are activated by laser to create metallic nuclei at these locations. The nuclei are used in a further deposition process, in particular in an electrodeposition process, to form a metallic layer or a metallic and gold-containing layer sequence.
In another aspect for creating a first and a second conductive path, the cover area and at least a portion of the side surface of the perimeter and the top edge of the perimeter are metallized. An etch resist is then applied to the cover area, and the perimeter, and laser-induced exposure of the etch resist is used to pattern the first, second, and third portions in the metallized areas of the perimeter. The unexposed areas are then removed and the metallization is removed by etching, for example.
In another aspect, the injection-molded cover plate is produced by two-component injection molding in two shot molding stages. One plastic forms the base body, while another can be metallized and forms the conductor track layout. There are two common methods for this, known as the PCK and SKW processes. Depending on the process, the metallizable plastic must be activated.
Among other things, a layer with copper is used as the material of the conductor path. Copper is also suitable as a nucleus for depositing a layer sequence as described above. In one aspect, the layer sequence is a Cu-Ni-Au layer with gold as the top layer. The thickness of the trace can vary in the individual sections, and is for example between 200 μm and 500 μm.
Another aspect relates to the step of forming an optical element. In this step, a material of the optical element is laser-induced or electrolytically removed, in particular in the area of the conductive path or on the cover area, so that the material of the optical element remains only in the area of the opening.
In one aspect, to create the optical element, the cover plate is placed in a bottom mold, particularly made of a UV transparent material. The bottom mold may be planar in one example, or structured (e.g., with protrusions or bulges) in another example, such that a lenticular optical element may be formed. In this case, the placement is such that the patterning is over the opening of the cover plate. A transparent optical element material is then placed in the cavity and opening in the cover plate. This can be done by dispensing, jetting or any other suitable means. In particular, the amount of material is selected to be substantially equal to a volume of the opening relative to the top and bottom edges of the cover area, or the volume including a volume of the bottom plate. More generally formulated, the quantity is chosen such that the upper side of the later optical element is flush with the upper side of the cover area.
Optionally, a cover mold made of a UV transparent material in particular can then be applied to fill the cavity of the cover plate. The transparent material of the optical element is cured and then the cover mold and bottom mold are removed. The cover mold and bottom mold can be made of PDMS, for example.
Alternatively, in another aspect, the step of forming an optical element may comprise the steps of:
In this manufacturing variant, the optical element is manufactured separately and then glued into the opening and onto the step in particular. The material quantity of the adhesive is selected accordingly. Excess adhesive can flow into the bulge. It is also possible to fill any gap caused by manufacturing tolerances with material in a process following the gluing step, so that the gap is planarized.
Another aspect relates to the step of applying a loop-shaped interlock circuit. In this step, a conductive material, for example a silver-based conductive polymer, is applied to the optical element in the edge region, with the ends in electrical connection to the conductive tracks, thus electrically coupling them to each other. A dispensing process, a jet process, a laser-induced transfer process or another suitable application process can be used for this purpose. Suitable materials include conductive silver, a conductive resin or a conductive polymer doped with a metal such as silver.
In one aspect, the end portions of the loop-shaped interlock circuit may be disposed on the first and second conductive paths, thereby electrically connecting them. To this end, a width of the interlock circuit may be less than a width of the first or second conductive path. A thickness of the interlock circuit may be in the range of 100 μm to 200 μm. Generally, however, the thickness and also the width of the interlock circuit are smaller than the corresponding dimension of the conductor tracks.
The method may also be provided for a plurality of cavity forming cover plates. Thus, in one aspect, the step of providing at least one injection molded cavity forming cover plate comprises providing a plurality of interconnected cavity forming cover plates arranged in rows and columns. The further steps are then performed for each cover plate of the plurality of cover plates, preferably in parallel. In addition, after completion of the optical element and the interlock circuit, the plurality of interconnected cover plates arranged in rows and columns each forming a cavity can be separated.
As mentioned above, the first and second traces may have a thickness in the range of 200 μm to 500 μm. The interlock circuit may include a smaller thickness, particularly in the range of 100 μm to 200 μm.
Another aspect relates to an optoelectronic device. This comprises a cover plate made according to the aspects and methods proposed herein. Further, an optoelectronic and light emitting device is disposed in the cavity. This has a light emitting surface facing the optical element. Thus, the loop-shaped interlock circuit is arranged between the optical element and the light-emitting surface of the optoelectronic component. It is further proposed to electrically couple the optoelectronic component to the interlock circuit in such a way that the component is switched off when the interlock circuit is interrupted.
In one embodiment, the optoelectronic device is a VCSEL or a laser.
In the following, the invention is explained in detail with reference to the drawings by means of some embodiments. Thus show:
The following embodiment examples concern various aspects and combinations thereof according to the proposed principle. In this context, the embodiment examples are not generally shown to scale. Likewise, various elements may be shown enlarged or reduced in size to emphasize individual aspects. However, it will be understood by those skilled in the art that the aspects illustrated herein may be combined with each other in the various embodiments and process steps without detriment to the inventive concept. Some aspects show a regular structure or shape. It should be noted here that slight differences and deviations from the ideal shape occur in practice, but without this being contrary to the inventive idea.
The inventors have recognized that a change in the manufacturing process, as described in the following figures, results in a reduction in mechanical stress, thereby allowing a reduction in thermally-induced displacement of the optical element relative to the cap. This makes separation of the optical element from the cap less likely. In addition, this effect can be favored by the use of mechanical anchors, mechanical stress both during manufacturing and during a subsequent operation is thus reduced, leading on the one hand to an increase in component reliability and on the other hand to an improved production yield.
For this purpose, it is proposed, among other things, to arrange the electrical conductor loop as well as the optical element on the same side as an optically active structure. This means that there is no need to glue over the conductor loop or the interlock circuit, so that this component is omitted from an overall thermo-mechanical consideration.
In the edge area 180 and thus above the opening, an optical transparent element 17 is arranged, the manufacturing method of which will be explained in detail below. In addition, a circumferential conductor loop 16, which represents an interlock circuit, is located in the edge region 180 on the optical element 17. The conductor loop 16 is electrically connected with its end regions 161 to a first conductor track 14 and a second conductor track 15, respectively. The first and second conductive traces thus electrically connect the interlock circuit 16. Damage to the interlock circuit 16 results in either an increase in resistance or other parameter change, such as a drop in current or an increase in voltage across the conductive traces 14 and 15. First and second conductive traces are applied as a metallic interconnect to the surface of the cover area 11, the side walls 13b, and the top edge of the perimeter 13a. Specifically, each conductive trace includes a first conductive trace section 141 and 151, respectively, applied to the cover area. A second section 143 and 144 (not shown here) runs along the inner sidewall 13b to the top edge 13a, where it forms the third section 143 and 153, respectively. This metallic interconnect allows the conductor loop and interlock circuit 16, respectively, to be routed outwardly or connected to an opto-electronic device to secure operation of the opto-electronic device.
For example, such a sequence of layers can consist of copper, nickel and a top gold layer.
Other ways of creating traces, such as those shown in
For example, instead of the laser-induced process proposed here, a two-component injection molding process can also be provided for the workpiece. In this process, a first metallizable plastic is prepared which reproduces the conductor track layout. However, this metallizable plastic is not itself electrically conductive, but is activated by various measures in a later step, as already shown above. A metal layer or metal layer sequence can be applied to the then metallized surface. The second plastic is non-metallizable, whereby the mold is finally filled by the second non-metallizable plastic and thus predetermined.
Another method of production is by means of an embossing process in which the existing conductive tracks are applied to and bonded to the plastic mold as a surface-modified metal foil by means of a carrier tool using pressure and heat. Although this process is particularly simple, one difficulty is that it is difficult to create side surfaces with it as in the embodiment presented. This is why this process is particularly suitable for simple planar designs. Equally possible would be processes such as film back injection or direct conductor drawing, in which metals such as copper are melted and then sprayed or otherwise raised onto the substrate materials using compressed air or inert gas. Depending on the size and design of the package, different steps and processes can thus be used to create the first and second conductor tracks.
In a subsequent step after placing the covers in the bottom mold, a liquid transparent material OEM is now introduced into the opening and onto the edge area of the opening. The amount of material is chosen so that the volume is substantially equal to the volume of the opening 18 as well as the edge area 180. In this manner, the material so introduced forms a substantially planar surface with the cover area of the cover area. The transparent material OEM may be, for example, a transparent polymer, acrylate or other transparent plastic. In this context, it is convenient to select a transparent material whose coefficient of thermal expansion is substantially the same as the coefficient of expansion of the surrounding plastic of the cover. In this way, a thermomechanical load on the component during an operation is reduced.
In addition, the cover and bottom molds are configured such that the optical material 17 does not adhere or stick to these molds even after curing, so that both molds can be removed after curing without damaging the optical element. As a result, the optical element 17 is thus introduced into the opening as a transparent liquid or viscous material and cured so that it is intimately bonded to the cover area. In some embodiments, not shown here, the perimeter may additionally have small hooks or a rough surface that improves adhesion of the material OEM and the optical element with the cover area 11.
After the lid mold and optionally also the base mold have been cured and lifted off, a so-called laser deflashing is carried out in this embodiment. Excess transparent material, particularly in the area of the conductor tracks, is removed by laser so that subsequent electrical contact with the interlock circuit is ensured. In addition, unevenness in the material can also be evened out in this way. At the same time, laser deflashing can be used to activate the corresponding area of the respective conductor tracks and thus prepare them for a subsequent metal-to-metal connection.
In
As shown in this embodiment, a width of the interlock circuit 16 is significantly smaller than the corresponding width of the conductive tracks 14 or 15. The thinner embodiment, for example in the range of less than 10 μm to 100 μm, ensures that even slight damage to the optical element will cause the interlock circuit 16 to unravel and thus break the electrical connection.
For example, it is quite possible to design it in a meandering shape, i.e. with several loops. If possible, the interlock circuit can also be drawn completely over the opening, in particular if this does not impair the light guidance or only insignificantly. In this way, direct damage to the optical element 17 in the opening can also be detected without damage in the edge region.
The conductor loop 16 is arranged above the perimeter 180 and is connected in the area 160 to the conductor tracks not shown here. The distance between the optoelectronic component 70 and the optical element 17 with the interlock circuit 16 mounted thereon also ensures that the interlock circuit 16 can be safely torn off if the optical element is damaged, thereby severing the connection. The optical element is also electrically coupled to the conductive paths 14 and 15 via bonding wires or other electrically conductive connections 72.
In one operation of this arrangement, a laser light is now generated in the laser 70 and emitted to the outside via the optical element 17. At the same time, a voltage is applied to conductive paths 14 and 15 and the resistance or other electrical parameter is evaluated. Conductive paths 14 and 15 can also be used directly as a current supply for the optical element.
In the event of damage to the optical element 17, the interlock circuit 16 now ruptures at one point and the electrically conductive connection between the conductor tracks 14 and 15 is interrupted. This interruption manifests itself, for example, in an abrupt breaking of a current through the conductive tracks or an increase in the resistance or voltage across the interlock circuit. In the first case, if power is supplied to the device 70 via the conductive traces 14 and 15, the disconnection of the interlock circuit directly shuts down the device. Alternatively, the resistance, voltage, or current flow across traces 14 and 15 can be evaluated and, if there is a change from a set point, the device can be electronically turned off.
In contrast to the previous example, however, a bulge 181 is still provided. An optical element 17, which has already been manufactured in advance, is now inserted into the opening 18 and firmly bonded in the edge area 180 by means of adhesive. In one aspect, the bulge 181 now serves to receive excess adhesive. In addition, as shown here, the optical element 17 is made with slightly smaller dimensions than the dimension of the edge region 180. This results in a small gap between the edge of the optical element 17 and the edge of the perimeter 180 forming the cover area. Depending on the application, this gap is filled with an adhesive or with another plastic or a combination of both, leaving the excess plastic or adhesive in the bulge 181. Thus, the bulge 181 serves as a buffer for excess adhesive or other plastic.
In a first step according to
Then, as shown in
As shown in
After curing, optional laser deflashing may be performed to remove material from the end regions of the traces from the lens potting or bonding step. Next, in step 7D, the interlock circuit can be applied to the optical element 17, such as a lens, by jetting or dispensing or other suitable processes. The end portions 161 of the interlock circuit 16 are electrically conductively connected to the end portions of the first sections 141 and 151, respectively. The material of the lens, as well as the material in the plastic, is thereby selected in its height such that this substantially closes with the cover area. As a result, the interlock circuit runs essentially planar in the area of the perimeter up to the end area of the respective conductor track section 141 or 151. Accordingly, a risk of the conductor loop 16 breaking off is already reduced during the manufacturing process.
The resulting structure in
The methods and embodiments proposed here can be combined in any way without this being detrimental to the idea of the invention. By designing the conductor loop or the interlock circuit on the surface of the optical element, a thermally induced stress is reduced. The conductor loop and the interlock circuit as well as the optically active structure are now located on the same side of the optical element. This also eliminates the need to bond over the conductor loop.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 124 008.2 | Sep 2020 | DE | national |
The present application is a national stage entry from International Application No. PCT/EP2021/073917, filed on Aug. 30, 2021, published as International Publication No. WO 2022/058149 A1 on Mar. 24, 2022, and claims priority to DE application 10 2020 124 008.2 filed Sep. 15, 2020, the disclosures of all of which are hereby incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/073914 | 8/30/2021 | WO |
