JPH0831848A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the creeping distance from being shortened due to flow-out of solder while preventing a short circuit due to adhesion of a solder ball when a semiconductor chip is soldered to a copper coating pattern formed on an insulating substrate. CONSTITUTION:A copper coating 2 is heated locally through irradiation with laser light, for example, to form a copper oxide film 8 and the unoxidated region thereof is soldered with a semiconductor chip, a terminal conductor, etc. The level difference from the oxide film prevents the solder from flowing out and a solder ball does not adhere easily onto the oxide film and it can be removed easily even upon adhesion thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device for electric power, in which a semiconductor element is fixed on a support plate used for heat dissipation and electrical connection by soldering.

[0002]

2. Description of the Related Art In a semiconductor device including a power semiconductor element, an insulating material made of ceramic or the like as a supporting plate is used for discharging heat generated in a semiconductor element body or for energizing electrodes on the semiconductor element body. The semiconductor element body is fixed to the support plate by soldering the copper film pattern on the substrate and the electrode on the semiconductor element body. For such soldering of the semiconductor element body and the supporting plate, a direct bonding method in which the copper coating surface of the supporting plate is covered with solder and the semiconductor element body is placed on the molten solder by an automatic hand and soldered There is a continuous soldering method in which a semiconductor element body is placed on a copper coating surface of a support plate via solder, fixed by a positioning jig, and passed through a hydrogen reducing atmosphere furnace for soldering.

[0003]

When soldering by the conventional method, if the processing temperature is too high, the viscosity of the molten solder becomes low, and the solder will flow out and the amount required for brazing cannot be secured. In particular, in the case of multi-model mixed production, the product dimensions are various and the difference in heat capacity is large, so it is necessary to set the temperature at which the solder has completely melted and solder is hard to flow out of the above two methods. Both are very difficult. For example, as shown in FIG. 3, when the semiconductor chip 4 is soldered to the copper coating 2 on the ceramic substrate 1 with the solder 3, if the processing temperature is set to be slightly higher in order to completely melt the solder, the solder 3 Not only the required solder thickness cannot be ensured due to the flow-out, but also the creepage distance of the insulating portion between the adjacent copper coating pattern 21 decreases, which causes a problem of insufficient insulation. As shown in FIG. 4, the short circuit problem between the copper coating patterns also occurs due to the adhesion of the solder balls 30 caused by the scattering of the molten solder.

An object of the present invention is to solve the above-mentioned problems and to prevent insufficient insulation due to a decrease in creepage distance of an insulating portion during brazing for fixing a semiconductor element body, or due to adhesion of solder balls. It is an object of the present invention to provide a method for manufacturing a semiconductor device that does not cause a short circuit problem.

[0005]

In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor device, which includes a step of fixing at least a semiconductor element body to a metal layer region of a surface of a support plate by brazing, The surface of the metal layer is selectively heated to form a metal oxide layer leaving a predetermined region, and the semiconductor element body is brazed to the exposed region of the metal surface.
Irradiation with laser light is effective for selectively heating the surface of the metal layer. It is preferable that at least a part of the metal layer in the thickness direction is made of copper.

[0006]

[Function] By forming a metal oxide layer on the surface of the metal layer by selective heating, a step is generated between the surface of the oxide layer and the exposed surface of the metal layer, and the surface tension of the molten wax during brazing. The action also adds to the flow of wax. Also,
Even when solder balls and the like are scattered, it becomes difficult to adhere to the oxide surface, and even if they adhere, the adhesive force is low.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. The manufactured semiconductor device is shown in FIGS.
As shown in FIG. 2, it includes two power transistor chips 4 as power semiconductor elements, and each chip 4 is fixed by solder 31 on the pattern of the copper coating 2 on the ceramic substrate 1. In addition, on the copper coating 2
The terminal conductor 5 shown by the dotted line in FIG. 5B is fixed by the solder 32 at the position 51 on the support plate 1 shown by the dotted line in FIG. The terminal conductor 5 penetrates the lid 6 of the resin container and is drawn out of the container. The copper coating 7 is also formed on the back surface of the substrate 1.

In order to manufacture this semiconductor device, FIG.
A supporting plate as shown in (a) and (b) was used. This support plate has a thickness of 0.
A pattern of the copper film 2 having a thickness of 3 mm and a copper film 7 having a thickness of 0.2 mm are formed on the entire back surface. Next, as shown in FIGS. 1 (a) and 1 (b), a portion which is not used for soldering the copper coating 2 on the surface of the support plate, that is, a portion 41 where the chip 4 is fixed and a terminal conductor 5 is fixed. Y in parts other than
The copper oxide film 8 having a thickness of 50 μm was formed on the surface by locally heating by scanning the AG laser beam. As shown in FIG. 5, the semiconductor chip 4 was soldered on the support plate to the exposed surface 41 of the copper coating 2 by the direct bonding method or the continuous soldering method using the high temperature melting solder 31.
Next, the terminal conductor 5 was soldered to the exposed surface 51 of the copper coating 2 using the low temperature melting solder 32. High temperature molten solder 31
Has a melting point of about 300 ° C, Pb93.5%, Sn5%, Ag
As the solder having a composition of 1.5% and the low temperature melting solder 31, a solder having a composition of Pb 37% and Sn 63% with a melting point of about 185 ° C. was used. In any case of soldering, the solders 31 and 32 did not flow out of the soldering points 41 and 51, and the solder balls did not adhere.

Even when the surfaces of the copper coatings 2 and 7 were plated with Ni to prevent oxidation, the copper oxide film 8 could be formed on the surfaces by laser light irradiation, and the same effect was obtained.

[0010]

According to the present invention, the metal layer on the surface of the support plate is selectively heated by a laser beam or the like to form the metal oxide layer on the portion other than the brazing portion, so that the molten brazing material does not flow out. , The insulation creepage distance between the metal layer regions is secured. Further, the thickness of the solder is stable and the brazing strength is secured. Further, scattered brazing material such as solder balls is less likely to adhere to the surface of the oxide layer and can be easily removed even if it adheres, so that no short circuit occurs between the metal layer regions.

[Brief description of drawings]

1A and 1B show a state after an oxide film is formed on a semiconductor device support plate according to an embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a side sectional view.

2 shows a state before forming an oxide film on the support plate of FIG.
(a) is a plan view, (b) is a side sectional view

FIG. 3 is a side sectional view when solder flows out.

FIG. 4 is a side sectional view when solder balls are attached.

5A and 5B show a state after mounting a semiconductor device support plate according to the present invention, where FIG. 5A is a plan view and FIG. 5B is a side sectional view.

[Explanation of symbols]

 1 Ceramic Substrate 2, 7 Copper Coating 31 High Temperature Melting Solder 32 Low Temperature Melting Solder 4 Semiconductor Chip 41 Semiconductor Chip Fixing Point 5 Terminal Conductor 51 Terminal Conductor Fixing Point 8 Copper Oxide Film

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device, which includes a step of fixing at least a semiconductor element body to a metal layer region on a surface of a support plate by brazing, the surface of the metal layer being selectively heated to leave a predetermined region. A method of manufacturing a semiconductor device, comprising forming a metal oxide layer and brazing a semiconductor element body to an exposed region of a metal surface. 2. The method of manufacturing a semiconductor device according to claim 1, wherein laser light is irradiated to selectively heat the surface of the metal layer. 3. The method of manufacturing a semiconductor device according to claim 1, wherein at least a part of the metal layer in the thickness direction is formed of copper.