JP6973109B2 - Manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to, for example, a technical field of a method for manufacturing a semiconductor device by bonding a semiconductor element and a heat spreader (hereinafter, appropriately referred to as "H / S") onto a base material and molding the semiconductor device with a resin.

As a method of this kind, there is one described in Patent Document 1. In this method, a semiconductor element is soldered onto a base material, and H / S is soldered onto the semiconductor element. Here, the H / S is provided with a metal one at a position between the semiconductor element and the heat sink for the purpose of diffusing the heat generated during the operation of the semiconductor element (particularly as a power device) and improving the heat dissipation efficiency. Then, a molded body is formed by molding the bonded portion of the semiconductor element and the H / S on the base material with a resin. Further, the mold body is cut so that the main surface of the H / S is exposed from the mold body. This cutting is performed until the main surface is exposed because the heat dissipation efficiency is lowered if the mold material covers the main surface. After that, the heat sink is fixed to the exposed main surface in this way.

Japanese Unexamined Patent Publication No. 2016-039206

However, according to this method, the semiconductor element and the H / S are joined by soldering before fixing the heat sink to the molded body. Therefore, if the main surface of the H / S is left as it is, it is between a plurality of elements. Does not flatten. This is because the H / S undergoes thermal shrinkage when the soldering heat is cooled, resulting in a step or a dimensional tolerance between the elements. In particular, since the resin is molded while including the heat shrinkage of the solder, this step or dimensional tolerance becomes so large that it cannot be ignored. Therefore, in the process of cutting the mold body so as to reduce the step or the dimensional tolerance, the mold body is first cut until the main surface of the H / S is exposed, and then even the exposed main surface of the H / S is exposed. By cutting appropriately, flattening is achieved between the main surfaces of the plurality of H / Ss, and then the heat radiation plate is fixed to the main surfaces. In this way, by cutting the molded body or deleting the main surface of the H / S as appropriate, cleaning after cutting and periodic replacement of cutting tools are performed, and the number of processes increases accordingly. There is a technical problem of high cost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device, which can suppress an increase in the number of steps relatively easily.

In order to solve the above-mentioned problems, the method for manufacturing a semiconductor device according to one aspect of the present invention has a plurality of locations on at least one surface of a flat plate-shaped base material, between the base material and the semiconductor element, and the semiconductor. The step of joining the element and the heat spreader with solder, and the step of measuring the height of the outer surface of the joined heat spreader facing the opposite side of the joined semiconductor element at each of the plurality of points, and the above-mentioned measurement. A laminated structure in which the base material, the semiconductor element, and the heat spreader are laminated on an elastic sheet whose layer thickness is set so as to complement the variation in height between the plurality of locations and which functions as a heat dissipation plate. Further, in the internal space of the mold including the elastic sheet, the pressing surface and the elasticity are formed by arranging them facing the outer surface at each of the plurality of locations and pressing the pressing surface of the mold onto the outer surface. A step of sealing the layers of the sheet and the layers of the elastic sheet and the outer surface, respectively, and a state in which the layers are sealed, by injecting a mold resin into the mold and curing the laminated structure. It is provided with a process of applying a mold.

FIG. 5 is a schematic cross-sectional view showing a process of joining a semiconductor element and H / S to a lead frame with solder in an embodiment. It is a schematic cross-sectional view which shows the process of setting an elastic sheet (that is, a heat dissipation sheet) in a mold in an embodiment. FIG. 5 is a schematic cross-sectional view showing a step (early stage) of sealing an elastic sheet by pressing it against the outer surface of an H / S with a mold in an embodiment. FIG. 5 is a schematic cross-sectional view showing a step (the final stage thereof) of sealing an elastic sheet by crimping it to the outer surface of the H / S with a mold in the embodiment. It is a schematic cross-sectional view which shows the process of applying a mold in a mold in an embodiment. It is a schematic cross-sectional view which shows the process of removing a molded body from a mold in an embodiment. FIG. 5 is a schematic cross-sectional view showing a step of attaching a pin fin plate to a main surface of an elastic sheet exposed from a semiconductor device which is a molded body in an embodiment.

A method for manufacturing a semiconductor device according to an embodiment will be described with reference to FIGS. 1 to 7. Here, FIGS. 1 to 7 show step by step each step of the manufacturing method according to the embodiment.
As shown in FIG. 1, first, the semiconductor element 13a constituting the power device is bonded by the solder 12a on one surface (upper surface in the middle of FIG. 1) of the lead frame 11 which is an example of the base material, and further, the surface of the semiconductor element 13a. Metallic H / S15a is joined to (upper surface in FIG. 1) by solder 14a. On the other hand, on the other surface of the lead frame 11 (lower surface in FIG. 1), the semiconductor element 13b constituting the power device is bonded by the solder 12b, and further, the metal H is attached to the surface of the semiconductor element 13b (lower surface in FIG. 1). / S15b is joined by solder 14b.

As a result, the laminated structure 10 including the lead frame 11, the semiconductor elements 13a, 13b, H / S15a, and 15b is constructed at a plurality of places of the lead frame 11. The plurality of laminated structures 10 are constructed at a plurality of locations on one surface and the other surface of the lead frame 11 according to the specifications of the semiconductor device to be manufactured, and are regarded as one element substrate 1. As will be described in detail below, a semiconductor device is manufactured by attaching various members having a heat dissipation function to the element substrate 1 and applying a mold having an insulating function to almost the entire area.

At this stage, the outer surface (upper surface in FIG. 1) of the H / S 15a is not flat at the plurality of locations (in other words, among the plurality of laminated structures 10). Similarly, the outer surface (lower surface in FIG. 1) of the H / S 15b is not flat at the plurality of locations.

More specifically, the height H1a of the outer surface of the H / S 15a in one laminated structure 10 (the laminated structure 10 on the right side in FIG. 1) and the other laminated structure 10 (the laminated structure 10 on the left side in FIG. 1). Due to its nature, it does not completely match the height H2a of the outer surface of H / S15a. Alternatively, there is a non-negligible height difference between the two. Similarly, the height H1b of the outer surface of the H / S 15b in one laminated structure 10 and the height H2b of the outer surface of the H / S 15b in the other laminated structure 10 do not completely match in nature. Alternatively, there is a non-negligible height difference between the two. This is because the H / S 15a and 15b have a step or a dimensional tolerance between a plurality of locations due to heat shrinkage when the heat of soldering is cooled. That is, since the thickness of the solder after cooling is not uniform among the plurality of locations, such a step is generated.

Therefore, in the present embodiment, after soldering, the heights H1a and H2a of the outer surface of the H / S15a and the heights H1b and H2b of the outer surface of the H / S15b are measured at a plurality of points, respectively. The measurement here is preferably performed by a non-contact type distance measuring machine in order to avoid fine mechanical damage and adhesion of fine dust and the like to the outer surfaces of the H / S 15a and 15b.

As shown in FIG. 2, next, the elastic sheet 31a, in which the layer thickness is set so as to complement the variation between the plurality of locations of the measured heights and functions as at least a part of the heat sink, 31b (in other words, a heat sink) is prepared. That is, there are a plurality of differences in the heights of the outer surfaces of the elastic sheets 31a and 31b facing the outer surfaces of the H / S 15a and 15b facing opposite to the outer surface of the H / S 15a and 15b. A plurality of elastic sheets 31a having layer thicknesses t1a and t1b set according to the variation in the height of the outer surface of the H / S 15a are prepared so as to be eliminated or reduced among the plurality of elastic sheets corresponding to the above. A plurality of elastic sheets 31b having layer thicknesses t2a and t2b set according to the variation in the height of the outer surface of the H / S 15b are prepared.

In other words, the sum of the layer thickness of H / S15a (see FIG. 1) and the layer thicknesses t1a and t1b of the elastic sheet 31a is equal among the plurality of locations so that the layer thickness t1a of the plurality of elastic sheets 31a is equal. t1b is set. Similarly, the sum of the layer thickness of H / S15b (see FIG. 1) and the layer thicknesses t2a and t2b of the elastic sheet 31b is equal among the plurality of locations so that the layer thickness t2a of the plurality of elastic sheets 31b is equal. t2b is set.

The plurality of elastic sheets 31a whose layer thickness is set in this way are the pressing surfaces of the upper movable nesting 41a (the surface facing downward in FIG. 2) at the positions where they face each of the corresponding H / S15a. Is fixed to. The plurality of elastic sheets 31b are fixed to the pressing surface (the surface facing upward in FIG. 2) of the lower movable insert 41b at a position facing each of the corresponding H / S 15b.

The elastic sheets 31a and 31b are typically made of an insulating resin, and have a suction force (adsorption force by vacuum exhaust) through an exhaust passage 45 having a plurality of holes in the upper movable insert 41a and the lower movable insert 41b, respectively. That is, it is fixed to the pressing surface of the upper movable insert 41a and the lower movable insert 41b by the vacuum chuck). Alternatively, instead of fixing by such vacuum exhaust, the elastic sheet 31a. The 31b may be formed by being applied to the pressing surfaces of the upper movable insert 41a and the lower movable insert 41b so as to have a predetermined film thickness, respectively.

Such elastic sheets 31a and 31b are made of, for example, an insulating heat conductive material containing boron nitride and alumina based on an epoxy resin. However, the material is not limited to the epoxy resin as long as it is excellent in heat dissipation or thermal conductivity, electrical insulation, and physical and chemical stability required for semiconductor devices in addition to elasticity. .. It can be considered that the elastic sheets 31a and 31b have an electrical insulating property, so that a structure in which a part of the mold resin 50 having the same electrical insulating property is replaced with the elastic sheets 31a and 31b is possible.

In this embodiment, instead of measuring the heights H1a and H2a of the outer surface, the height from the outer surface of the H / S15a to the outer surface of the H / S15b, in other words, each laminated structure 10 (FIG. The total layer thickness in the stacking direction (that is, {H1a + layer thickness of lead frame 11 + H1b} or {H2a + layer thickness of lead frame 11 + H2b} in FIG. 1) may be measured. Also in this case, the layer thicknesses of the elastic sheets 31a and 31b that complement the variation may be set / selected based on the measurement result.

As shown in FIG. 3, the elastic sheets 31a and 31b having the layer thickness set in this way are evacuated by the vacuum pump 48 through the exhaust passage 45 (see FIG. 2) and the exhaust pipe 47 (see FIG. 3). As a result, it is vacuum-sucked to the pressing surface of the mold 40 (that is, the pressing surface of the upper movable insert 41a and the lower movable insert 41b constituting the mold 40). Here, the mold 40 includes an upper mold movable insert 41a and a lower mold movable insert 41b (see FIG. 2) incorporated in the center of the upper and lower mother molds 42a and 42b.

The alignment protrusion 43 provided on the lower mother die 42b is fitted into the alignment mark (that is, the alignment hole) of the lead frame, and the members for sealing and molding are accurately positioned with each other. Depending on the mold 40, the plurality of elastic sheets 31a and 31b (those having different layer thicknesses) are fixed to the pressing surfaces of the upper mold movable insert 41a and the lower mold movable insert 41b, and a plurality of H / The outer surfaces of S15a and 15b (that is, surfaces having different heights) are pressed from behind. Depending on the structure of the mold, it is also possible to adopt a method of directly fixing the elastic sheet to the upper and lower mother molds.

As shown in FIG. 4, the elastic sheets 31a and 31b are then pressed onto the outer surface of the H / S 15a and 15b by the mold 40 as shown by the down arrow 43a and the down arrow 43b in the figure. .. As a result, the elastic sheets 31a and 31b are compressed, and the layers between the pressing surface of the mold 40 and the elastic sheets 31a and 31b (the outer surface thereof) are sealed. At the same time, the elastic sheets 31a and 31b are compressed, and the layers between the elastic sheets 31a and 31b (the surface opposite to the outer surface thereof) and the outer surfaces of the H / S 15a and 15b are sealed, respectively. Then, despite the variation in the heights of the outer surfaces of the H / S 15a and 15b, the pressing surface of the mold 40 and the layers between the plurality of elastic sheets 31a and 31b (each having a layer thickness that complements the variation). With respect to the above, it is possible to easily and firmly seal the layers of the plurality of elastic sheets 31a and 31b and the plurality of H / S 15a and 15b (with the above-mentioned variation) without gaps or firmly.

Next, as shown in FIG. 5, in the sealed state as described above, the mold resin 50 is injected into the mold 40 and cured to form a mold for each laminated structure 10. Specifically, for example, the epoxy resin is transfer-molded under the condition that the resin pressure is 10 Mpa or less and the mold temperature is less than 210 ° C. as a condition for avoiding damage to the element substrate 1 (see FIG. 1). Then, since the elastic sheets 31a and 31b are compressed, the restoring force is also applied to the pressing surface of the mold 40 sealed without gaps and the layers between the plurality of elastic sheets 31a and 31b due to the restoring force or the elastic force. Alternatively, the mold resin can be prevented from entering the layers of the plurality of elastic sheets 31a and 31b and the plurality of H / S 15a and 15b that are sealed without gaps by the elastic force. Since the elastic sheets 31a and 31b and the mold resin 50 can be molded at the same time in this way, it is very convenient in manufacturing.

Next, as shown in FIG. 6, the mold 40 is removed. Then, the mold resin 50 does not remain on the outer surfaces of the plurality of elastic sheets 31a and 31b regardless of the thickness of the layer, and the outer surfaces of the plurality of elastic sheets 31a and 31b are thin and thin. Regardless, the heights are virtually or practically perfectly aligned. In addition, the parallelism of the outer surfaces of the elastic sheets 31a and 31b is secured according to the parallelism of the pressing surface of the mold 40, and the distance between the H / S 15a and 15b is also secured. At the same time, an inconvenient situation in which the mold resin 50 enters between the layers of the H / S 15a and 15b and the elastic sheets 31a and 31b and the thermal conductivity between the two is lowered is also prevented.

In this way, molding is executed including joining the elastic sheets 31a and 31b to the H / S 15a and 15b or molding the elastic sheets 31a and 31b. That is, the molding of the elastic sheets 31a and 31b or the joining to the H / S 15a and 15b and the insulation of the element substrate 1 (see FIG. 1) by the mold resin 50 can be executed in parallel at the same time. As a result, a semiconductor device 100 having elastic sheets 31a and 31b that function as at least a part of the heat radiating plate and having a resin-molded almost the entire area thereof is constructed.

Next, as shown in FIG. 7, the pin fin plates 60a and 60b, which constitute the heat sink together with the elastic sheets 31a and 31b, are attached to the elastic sheets 31a and 31b. The pin fin plates 60a and 60b each have a plurality of pin fins 61a and 61b, and are excellent in the wide cross-sectional area and the convection of cooling air. The pin fin plates 60a and 60b can efficiently dissipate heat generated by the semiconductor elements 13a and 13b during operation in cooperation with the H / S 15a and 15b and the elastic sheets 31a and 31b. For example, if the semiconductor device (see FIG. 7) constituting the power device is used for a power card related to a cooler installed in an inverter of an HV vehicle or an EV vehicle, a power card having high cooling performance can be obtained. Can be built.

As described above with reference to FIGS. 1 to 7, in the present embodiment, it is not necessary to cut the molded body or to appropriately delete the main surface of the H / S, and therefore it is not necessary to perform cleaning after cutting or a cutting tool for cutting. There is no need to perform regular replacement. As described above, by using the manufacturing method of the present embodiment, it is possible to manufacture a semiconductor device having excellent heat dissipation with a small number of steps.

Aspects of the invention derived from the embodiments described above will be described below.

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The method for manufacturing a semiconductor device according to one aspect of the present invention is to solder between the base material and the semiconductor element and between the semiconductor element and the heat spreader at a plurality of positions on at least one surface of the flat plate-shaped base material. A step of measuring the height of the outer surface of the joined heat spreader facing the side opposite to the joined semiconductor element at each of the plurality of locations, and a step of measuring the heights of the measured heights. An elastic sheet in which a layer thickness is set so as to complement variations between locations and functions as a heat dissipation plate includes the substrate, a laminated structure in which the semiconductor element and the heat spreader are laminated, and the elastic sheet. In the internal space of the mold, by arranging them facing the outer surface at each of the plurality of locations and pressing the pressing surface of the mold onto the outer surface, the layers between the pressing surface and the elastic sheet and the elastic sheet are pressed. A step of sealing each of the layers of the outer surface and a step of molding the laminated structure by injecting a mold resin into the mold and curing the layers in a state where the layers are sealed are provided. ..

In the above aspect, the semiconductor element and the H / S are laminated in this order on the surface which is both sides or one side of the base material, and solder between the base material and the semiconductor element and between the semiconductor element and the H / S, respectively. Joined at. Such lamination and soldering are performed at a plurality of locations on the surface of the base material, respectively. At this stage, the outer surface of the H / S is not flat at the plurality of locations. This is because the H / S undergoes thermal shrinkage when the heat of soldering is cooled, and a step or a dimensional tolerance occurs between a plurality of locations.

Therefore, after soldering, the height of the outer surface of the H / S is measured at each of a plurality of points. Typically, the height of the outer surface from the center surface in the surface or thickness direction of the base material or the height of the outer surface in the stacking direction from the reference plane, in other words, the semiconductor element, the heat spreader and the base material are laminated and bonded. The thickness of the laminated structure formed in the laminated structure is measured at a plurality of points.

Further, an elastic sheet is prepared in which the layer thickness is set so as to complement the variation between the plurality of locations of the measured heights and which functions as at least a part of the heat sink. That is, in the elastic sheet that is arranged to face the outer surface of the H / S, the difference in height of the outer surface facing the opposite side from the outer surface of the H / S corresponds to a plurality of elastic sheets. A plurality of elastic sheets whose layer thickness is variably set according to the variation in the height of the outer surface of the H / S are prepared so as to be eliminated or reduced between the two. That is, adjustments are made to the layer thickness of each of the plurality of elastic sheets so that the total of the layer thickness of the H / S and the layer thickness of the elastic sheet becomes equal among the plurality of locations. Such an elastic sheet is typically made of an insulating resin, and is applied to the pressing surface of the mold by a joining means (for example, the adhesive force of the material itself, the adhesive force of a separately applied adhesive, or vacuum exhaust. It is installed or applied in a form that is fixed by (adhesive force).

After that, the elastic sheet having the layer thickness set in this way is pressed from behind the elastic sheet onto the outer surface of the H / S by the pressing surface of the mold. By pressing the elastic sheet onto the outer surface of the H / S, the layers of the pressing surface and the elastic sheet and the layers of the elastic sheet and the outer surface of the H / S are sealed, respectively. Then, despite the variation in the height of the outer surface of the H / S, the layers of the pressing surface and the plurality of elastic sheets, and the layers of the plurality of elastic sheets and the plurality of H / Ss can be simplified. It is possible to seal tightly or without gaps.

Then, in the state of being sealed in this way, the mold resin is injected into the mold and cured to form a mold for the laminated structure. Then, the mold resin can be prevented from entering the pressing surface sealed without gaps and the layers of the plurality of elastic sheets, and the layers of the plurality of elastic sheets and the plurality of H / Ss sealed without gaps. As a result, when the mold is removed, the mold resin does not remain on the outer surface of the plurality of elastic sheets regardless of the thickness of the layer, and the outer surface of the plurality of elastic sheets has the layer thickness. Regardless of the thickness of the, the height is practically or practically perfectly aligned.

As a result, the cutting process for the mold resin or the like is eliminated, that is, the number of processes is increased or the cost is increased by cutting the molded body or deleting the main surface of the H / S as appropriate, which is extremely efficient. It will be possible to avoid it. Moreover, for example, it is not necessary to retrofit an insulating plate as a heat sink for the purpose of ensuring insulation between the semiconductor element or the like and the metal cooling device, and an elastic sheet or a heat dissipation sheet made of an insulating resin is directly placed in the mold. Since the elastic sheet can be molded on the H / S at the same time as coating or installation and molding, the manufacturing efficiency is extremely high.

The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of claims and within the scope not contrary to the gist or idea of the invention that can be read from the entire specification. The manufacturing method is also included in the technical scope of the present invention.

1 ... Element substrate, 10 ... Laminated structure, 11 ... Lead frame, 12a, 12b, 14a, 14b ... Solder, 13a, 13b ... Semiconductor element, 15a, 15b ... H / S (heat spreader), 31a, 31b ... Elastic sheet ( Heat spreader), 40 ... mold, 50 ... mold resin, 60a, 60b ... pin fin plate

Claims (1)

A step of soldering between the base material and the semiconductor element and between the semiconductor element and the heat spreader at a plurality of locations on at least one surface of the flat plate-shaped base material.
A step of measuring the height of the outer surface of the bonded heat spreader facing the opposite side of the bonded semiconductor element at each of the plurality of locations.
The base material, the semiconductor element, and the heat spreader are laminated on an elastic sheet whose layer thickness is set so as to complement the variation of the measured height between the plurality of locations and which functions as a heat dissipation plate. In the inner space of the mold including the laminated structure and the elastic sheet, the pressing surface is arranged to face the outer surface at each of the plurality of locations and pressed onto the outer surface by the pressing surface of the mold. And the steps of sealing the layers of the elastic sheet and the layers of the elastic sheet and the outer surface, respectively.
A method for manufacturing a semiconductor device, which comprises a step of forming a mold on the laminated structure by injecting a mold resin into the mold and curing the layers in a state where the layers are sealed.

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