JPH05175380A - Hybrid integrated circuit and its production - Google Patents

Abstract

PURPOSE:To prevent a solder cavity generated on the interface between a heat sink, which is firmly fixed on a metal plate through a solder layer, and the solder layer. CONSTITUTION:A slight quantity of solder cream 5 or flux is applied on a solder layer 4 formed at a prescribed position on a conducting path 3 formed in a desired shape on a substrate, a heat sink 6 mounted with a power semiconductor element is mounted on the solder cream 5 or the flux and the heat sink 6 is firmly fixed on the solder layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid integrated circuit and a manufacturing method thereof, and more particularly to a hybrid integrated circuit in which a power semiconductor element is fixedly mounted via a heat sink and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 9, a hybrid integrated circuit having a heat sink is formed by etching a copper foil on a good thermal conductive hybrid integrated circuit board (21) such as an aluminum plate whose surface is insulated. The desired conductive path (22) is formed, and the fixing pad (23) is also formed on a part of the conductive path (22) at the same time. The fixing pad (23) is formed in substantially the same shape as the heat sink (24) fixed to the fixing pad (23), and the fixing pad (23) is made of a copper piece or the like.
, And the power semiconductor element (25) is fixed to the heat sink (24).

In the above structure, the fixing pad (23)
If another conductive path (22) is disposed adjacent to the heat sink (24) when the heat sink (24) is soldered to the fixing pad (23) by applying ultrasonic vibration to the board (2).
1) There was a risk that the resin layer on the surface became spherical and short-circuited with another adjacent conductive path (22). The above-mentioned problem can be easily solved by setting the amount of the solder cream to a relatively small amount, but in order to securely fix the heat sink and the fixing pad and reduce the thermal resistance to some extent, the amount of the solder cream is inevitable. There was an unsolvable problem of having to print a little more.

Various proposals have been made to solve such problems. First, as shown in FIG. 9, first, an expansion portion (26) is provided on at least one side of the fixing pad (23) to remove excess solder generated when ultrasonic vibration is applied to the expansion portion (2).
Absorb in 6). Secondly, as shown in FIG. 10, a groove (31) is provided on the side surface of the heat sink (30), and excess solder generated when ultrasonic vibration is applied is raised and absorbed through the groove (31). Such a proposal has already been made.

By the way, when a heat sink is soldered onto a pad, ultrasonic vibration is applied to the heat sink in order to suppress the generation of solder voids in the solder layer, so that the generation of voids in the solder layer is prevented. Can be suppressed to some extent.

[0006]

Although the above-mentioned proposal can prevent the problem of excessive solder caused by ultrasonic vibration, a new problem arises. That is, in the structure in which the expansion portion (26) is provided on the fixing pad (23) as shown in FIG. 9, the fixing pad (23) is a relatively large expansion portion that can surely absorb the excess solder. (2
6) must be formed, which reduces the mounting area and hinders downsizing of the hybrid integrated circuit.

Further, in the structure as shown in FIG. 10, the groove (31) of the heat sink (30) must absorb the solder by the rising development, and the thickness of the heat sink (30) must be made thick to some extent. There is a risk that the rising solder will stick up to the semiconductor chip fixed on the heat sink, resulting in a failure. Furthermore, in the structure shown in FIG. 10, a groove must be formed on the side surface of the heat sink (30), and a dedicated press punching step is required to form such a groove.

In any of the proposals, if the structure is such that ultrasonic vibration is applied to the heat sink to prevent the generation of solder voids, the above-mentioned excessive solder is inevitably generated and the above-mentioned problems cannot be solved. It is an issue. Furthermore, in the conventional structure, since the heat sink is formed larger than the power semiconductor element in order to apply ultrasonic vibration to the heat sink, as the power semiconductor element becomes larger, the heat sink is formed larger than the chip size as described above. This has been an obstacle to miniaturization of the hybrid integrated circuit.

[0009]

In order to solve the above-mentioned problems, a hybrid integrated circuit according to the present invention comprises a hard substrate excellent in good thermal conductivity and a metal layer having a desired shape formed on the substrate. A solder layer applied at a desired position on the metal layer, a solder cream or flux applied in a trace amount on the solder layer, and the solder and the solder cream or flux are melted and fixed on the metal layer. And a heat sink having a power semiconductor element mounted thereon, wherein the flux contained in the solder layer or the flux is left only near the peripheral edge of the metal layer.

On the other hand, the method of manufacturing a hybrid integrated circuit according to the present invention comprises the steps of preparing a metal substrate having excellent thermal conductivity and applying solder at a desired position on the substrate to form a solder layer. After applying a solder cream or flux onto the solder layer, a heat sink is mounted on the solder layer to melt the solder layer.

Further, in the method for manufacturing a hybrid integrated circuit according to the present invention, a step of preparing a substrate on which a conductive path having a desired shape is formed, cream solder is applied to a desired position on the conductive path, and the cream solder is applied. A step of melting and curing to form a solder layer, and after applying a small amount of solder cream or flux on the solder layer, mount a heat sink having a power semiconductor element fixed on the solder layer and heat the substrate. And a process.

[0012]

In the hybrid integrated circuit and the method of manufacturing the same configured as described above, a slight amount of solder cream or flux is applied to the solder layer to fix the heat sink, so that it occurs at the interface between the heat sink and the solder layer. The generation of solder voids (solder nests) can be significantly suppressed. As a result, the thermal conductivity between the heat sink and the solder layer can be optimized, and the heat dissipation effect of the heat sink can be maximized.

Further, by arranging only a small amount of solder cream or flux on the solder layer, it is possible to minimize the flux generated when the solder layer is melted when the heat sink is fixed. That is, the flux can be left only around the fixing pad of the heat sink, and the flux does not flow out to the periphery.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hybrid integrated circuit of the present invention and a method of manufacturing the same will be described below with reference to the embodiments shown in FIGS. As shown in FIG. 8, the hybrid integrated circuit of the present invention includes a substrate (1) having excellent thermal conductivity, an insulating layer (2) formed on one main surface of the substrate (1), and an insulating layer thereof. (2) A conductive path (3) having a desired shape formed on the solder layer, a solder layer (4) formed at a desired position on the conductive path (3), and a small amount of solder applied on the solder layer (4). It consists of a cream (5) and a heat sink (6) mounted on the solder layer (4).

The manufacturing process of the hybrid integrated circuit of the present invention will be described in detail below. First, as shown in FIG. 1, a substrate (1) on which a conductive path (3) having a desired shape is formed is prepared. For the substrate (1), a metal substrate such as aluminum having a thickness of about 2 mm whose surface is anodized is used in consideration of heat dissipation characteristics and workability. The substrate (1) at this manufacturing stage has a plane size of several to ten or more units of the hybrid integrated circuit device, and a slit (not shown) is formed in consideration of division into the unit hybrid integrated circuit device. .. This board (1)
On one main surface, a clad material composed of a thermosetting insulating resin having an adhesive property such as an epoxy resin and a copper foil having a thickness of about 35 μm is provided at a temperature of 150 ° C. to 170 ° C. and 5 per square centimeter.
It is hot pressed at a pressure of 0 to 100 kg. By this hot pressing process, the thermosetting insulating resin is completely cured to form the insulating layer (2) having a thickness of about 35 μm.

Then, the hot-pressed copper foil is etched into a desired shape to form a conductive path (3) having a desired pattern. The conductive path (3) has pads (3a) for fixing elements such as semiconductor elements, chip capacitors, chip resistors and heat sinks. Adjacent positions (about 0.2 to 0.5) of those pads (3a)
A conductive pattern (3b) for wiring is extendedly formed in (mm interval).

Next, as shown in FIG. 2, a solder cream (4a) is applied to a desired position of the pad (3a) to form a solder layer (4). The solder cream (4a) applied in this step is the pad (3a) to which the heat sink is fixed.
Although not shown in the drawing, only the pad to which the external lead is fixed is selected and printed using a means such as screen printing.

Solder cream (4
For a), since the surface of the pad (3a) may be oxidized, a solder cream (4a) containing an inorganic acid flux with strong surface activation is used. Therefore, after the cream (4a) is printed / melted / cured, the cream (4a) is washed to completely remove the flux to form the solder layer (4). Next, as shown in FIG. 3, the pad (3
A paste material such as solder paste or silver paste is screen-printed or potted on the pads (3b) other than a). Then, electronic components (7) such as chip resistors and chip capacitors are mounted on the solder paste,
Reflow and fix completely. Also, a small signal element is mounted on the silver paste and thermally cured to completely fix the small signal element.

Next, as shown in FIG. 4, a small amount of solder cream (5) or flux is applied onto the solder layer (4). In this embodiment, solder cream is used. As the solder cream (5), a solder cream whose melting point is lower than the melting point of the solder layer (4) is used, and is formed into a cream shape with a rosin-based flux. The solder cream (5) is dropped on one point of the substantially central portion of the solder layer (4).

Next, as shown in FIG. 5, a heat sink (6) is placed on the solder layer (4). The heat sink (6) is
For example, it is formed of a copper material, and its surface is plated with a metal such as nickel plating. A power semiconductor element (7) such as a power transistor is soldered to the upper surface of the heat sink (6). When this heat sink (6) is placed on the solder layer (4), as shown in FIG. 6, the solder cream (5) dropped on the solder layer (4).
The (flux) is temporarily spread to the peripheral portion (in the direction of the arrow) by the weight of the heat sink (6).

Next, as shown in FIG. 7, the substrate (1) is treated with about 20
The heat sink (6) is fixed on the solder layer (4) by heating to about 0 ° C. When the substrate (1) is heated, only the substantially central portion of the solder layer (4) coated with the solder cream (5) has good solder wettability, so that the central portion becomes a starting point of solder melting and solder of the solder cream (5). The ball (5a) and the solder layer (4) are fused and metal-bonded to the bottom surface of the heat sink (6). The bond gradually spreads radially from the central part to the peripheral part (in the direction of the arrow), and the flux (5b) in the solder cream (5).
Gradually becomes pushed out as the metal bond diffusion spreads. When the flux (5b) is extruded to the outside, the bottom surface of the heat sink (6) has good solder wettability, and as shown in FIG. 8, the solder (8) that is a fusion of the solder cream (5) and the solder layer (4) ) And the heat sink (6) are completely metal-bonded.

Flux (5b) of solder cream (5)
Are all removed from between the heat sink (6) and the fused solder (8) when the heat sink (6) is fixed. At this time, gas generated during melting of the solder or impurities such as dust are also removed to the outside together with the flux, so that no solder void is generated at the interface between the heat sink (6) and the solder (8).
Further, since the removed flux (5b) is in a small amount, it flows out only in the vicinity of the periphery of the pad (3a) to which the heat sink (6) is fixed, and does not flow out into the peripheral conductive path (3).

Although an aluminum substrate is used as the substrate (1) in this embodiment, a copper plate is used as the substrate (1) when used for high power. In this case, the insulating layer is not formed in the area where the heat sink is mounted, the solder layer is directly formed on the copper plate, and the heat sink having the DBC structure is fixed on the solder layer. Further, in the present embodiment, the solder cream (5) is applied on the solder layer (4), but the same action and effect can be expected by applying only flux other than the solder cream.

[0024]

As described above in detail, in the hybrid integrated circuit according to the present invention, a hard substrate excellent in good thermal conductivity, a metal layer having a desired shape formed on the substrate, and the metal layer are formed. A solder layer applied at a desired position, a small amount of solder cream or flux applied on the solder layer, and a power semiconductor element fixed on the metal layer by melting the solder and the solder cream or flux. And a flux contained in the solder layer or the flux is left only in the vicinity of the peripheral edge of the metal layer.

On the other hand, in the method of manufacturing a hybrid integrated circuit according to the present invention, a step of preparing a metal substrate having excellent thermal conductivity and a step of applying solder to a desired position on the substrate to form a solder layer. After applying a solder cream or flux onto the solder layer, a heat sink is mounted on the solder layer to melt the solder layer.

Further, in the method of manufacturing a hybrid integrated circuit according to the present invention, a step of preparing a substrate on which a conductive path having a desired shape is formed, and cream solder is applied to a desired position on the conductive path, and the cream solder is applied. A step of melting and curing to form a solder layer, and after applying a small amount of solder cream or flux on the solder layer, mount a heat sink having a power semiconductor element fixed on the solder layer and heat the substrate. And a process.

Therefore, according to the present invention, the generation of solder voids (solder nests) at the interface between the heat sink and the solder layer can be significantly suppressed. As a result, the thermal conductivity between the heat sink and the solder layer can be optimized, and the heat dissipation effect of the heat sink can be maximized. Further, according to the present invention, by arranging only a small amount of solder cream or flux on the solder layer, it is possible to minimize the flux generated when the solder layer is melted when the heat sink is fixed. That is, the flux can be left only in the vicinity of the fixing pad of the heat sink, and the flux does not flow out to the peripheral conductive paths, so that the cleaning step is not required. Further, the conductive pattern can be arranged adjacent to the vicinity of the pad of the heat sink, which can contribute to high integration.

Further, in the present invention, since it is not necessary to apply ultrasonic vibration to the heat sink as in the conventional case, the size of the heat sink can be made substantially the same as that of the chip-shaped pattern element, and the miniaturization can be minimized. The heat sink structure can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a hybrid integrated circuit of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 4 is a sectional view showing a manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 5 is a sectional view showing a manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 6 is a cross-sectional view showing a manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 7 is a cross-sectional view showing the manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 8 is a cross-sectional view showing a manufacturing process of the hybrid integrated circuit of the present invention.

FIG. 9 is a plan view showing a conventional heat sink structure.

FIG. 10 is a perspective view showing a conventional heat sink structure.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Kanakubo, 2-18 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Inventor, Kiyasu Sakai 2-18 Keihan Hondori, Moriguchi City Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A hard substrate excellent in good thermal conductivity, a metal layer having a desired shape formed on the substrate, a solder layer applied to a desired position of the metal layer, and a trace amount on the solder layer. A solder cream or flux applied to the solder and a heat sink mounting the power semiconductor element fixed on the metal layer by melting the solder and the solder cream or flux, and the flux contained in the solder layer. Alternatively, the hybrid integrated circuit is characterized in that the flux is left only in the vicinity of the peripheral edge of the metal layer. 2. A step of preparing a metal substrate having excellent good thermal conductivity, a step of applying solder to a desired position on the board to form a solder layer, and a step of applying solder cream or flux on the solder layer. After that, a step of mounting a heat sink on the solder layer and melting the solder layer is performed, the manufacturing method of the hybrid integrated circuit. 3. A step of preparing a substrate on which a conductive path having a desired shape is formed, a step of applying cream solder to a desired position on the conductive path, and melting and curing the cream solder to form a solder layer, A step of applying a small amount of solder cream or flux onto the solder layer, mounting a heat sink to which a power semiconductor element is fixed on the solder layer, and heating the substrate. Circuit manufacturing method.