JPH06349998A - Manufacture of molded semiconductor element - Google Patents

Abstract

PURPOSE:To prevent oxidation.corrosion of an exposed surface of a lead frame without necessity of Ni-plating by bringing potassium silver cyanide and water contained in hydrophilic organic material into contact with the surface of the frame, forming a surface film, and then fixing a semiconductor element to a mounting part of the frame with solder. CONSTITUTION:When a lead frame 1 is brought into contact with potassium silver cyanide and water contained in hydrophilic organic material, Ag 2 substituted for Cu is adhered in porous state to the Cu alloy frame 1, hydrophilic organic chain 3 is bonded to the Ag 2 to form a film 4. Thereafter, a semiconductor element 5 is fixed to a mounting part of the frame 1 via solder 6. The chain 3 of the film 4 is bonded to the Ag of a surface of the Cu to form a film having a high strength thereby to prevent oxidation. At the time of bringing it with melted solder, it doe not repel the solder due to hydrophilic properties of the organic film, the film is decomposed by heat of the solder, the solder is wetted with the Ag film, and the solder film having no pore is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold type semiconductor in which a semiconductor element body fixed on a metal substrate is covered with a resin, and terminal conductors connected to electrodes on the surface of the semiconductor element body are exposed from the resin. The present invention relates to a method of manufacturing an element.

[0002]

2. Description of the Related Art A molded semiconductor element such as a molded transistor has an advantage that it can be manufactured at low cost because a semiconductor body is sealed with a molding resin. There are two types of mold type semiconductor elements, a full mold type in which only the terminals are exposed to the outside of the resin, and a type in which the back surface of the metal substrate is also exposed in order to improve heat dissipation. The metal substrate and the terminals are the mount portion and the external lead portion of the lead frame made of copper, and are nickel-plated to avoid the oxidation or corrosion of the exposed copper surface.

[0003]

The Ni plating on the lead frame has a problem that the cost is considerably increased for the following reason. (1) It takes 7 to 10 minutes to process Ni plating having a thickness of 3 μm, resulting in an increase in man-hours.

(2) Since the wettability of the solder decreases due to the inclusion of phosphorus in the Ni plating, flux must be used when the solder film is formed by dipping the solder in the solder bath at the terminal part, and then cleaning. A step to do is also required. It is an object of the present invention to provide a method for manufacturing a mold type semiconductor device which does not require such problematic Ni plating.

[0005]

In order to achieve the above object, the present invention secures a semiconductor element body to a mount portion of a lead frame made of a Cu-based material, and fixes at least the tip of the outer lead portion of the lead frame. In the method for producing a mold-type semiconductor element that is exposed and sealed with a resin, water containing silver potassium cyanide and a hydrophilic organic substance is brought into contact with the surface of the lead frame to form a surface film,
It includes a step of fixing the semiconductor element body to the mount portion of the lead frame with solder. Then, after the step of fixing the semiconductor element body, the step of connecting the electrode on the surface of the semiconductor element body and the external lead portion of the lead frame by bonding of the conductive wire, the step of applying the bonding coating resin on the surface of the semiconductor element body, and It is effective to include a step of molding the sealing resin. Further, it is also effective to include a step of immersing the external lead portion exposed from the sealing resin in a solder bath.

[0006]

[Function] The lead frame is replaced with silver potassium cyanide (K [A
When contacted with water containing g (CN) ₂ ]) and a hydrophilic organic substance, Ag is substituted on the surface of Cu and the porous Ag film is covered with the organic film. The organic chains of the organic film
Bonds with Ag on the Cu surface to form a strong film and prevents oxidation, but when the molten solder comes into contact, the organic film is hydrophilic and does not repel the solder. It was disassembled and the solder wets the Ag film well,
Forming or soldering of void-free solder film is performed. Due to the above-mentioned antioxidation effect, it is possible to form a solder film or solder without a flux even after a certain amount of heat history after Ag substitution and organic film formation. Even in the mold-type element with the back surface of the substrate exposed, there is no discoloration due to oxidation of the exposed surface.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing process of a molded transistor according to an embodiment of the present invention will be described below with reference to the drawings. Since the lead frame produced by punching from the Cu alloy plate has poor wettability as it is, various degreasing treatments are performed as shown in FIG.
After neutralization and chemical polishing, K [Ag (CN) ₂ ]
In addition to 2 to 5 g / l, for example, in a pure water containing a hydrophilic organic substance having a specific organic chain such as Nippon Electroplating Engineers Co., Ltd. trade name Etrex W-AIS as a substitution preventing agent Surface treatment is carried out by immersing for about 30 seconds to 1 minute. This time is about 1/10 of the conventional Ni plating process. As a result, as conceptually shown in FIG. 1, Ag 2 substituted with Cu adheres to the Cu alloy lead frame 1 in a porous form, and the hydrophilic organic chain 3 is bonded to Ag 2 to form the film 4. After this, after washing with water and drying, the assembly process shown in FIG. 4 is started.

In another manufacturing process, np is applied to a silicon wafer.
After forming the n or pnp structure, the transistor chip obtained by cutting is die-bonded to the mount portion of the lead frame by soldering. 35 by molten solder
Since it is heated to about 0 ° C., the organic film 4 on the hydrophilic surface that does not repel solder is thermally decomposed, and as shown in FIG.
The Si chip 5 is joined by the solder 6 to the lead frame 1 having the substitution Ag 2 attached on its surface. At this time, since the surface of the lead frame 1 does not contain phosphorus and the substitution Ag2 exists, the wettability of the solder 6 is good and the generation of solder voids is small. After that, wire bonding, joint coating resin
(JCR) coating, curing of the JCR, and resin molding are performed. However, since the heat is not applied as much as during die bonding, the substitution Ag2 and the organic film 4 prevent oxidation. Therefore, after cutting the lead frame, it is not necessary to use the flux when immersing the external lead portion to be the terminal in the solder bath to form the solder film, and the washing step unlike the prior art is not required.

[0009]

INDUSTRIAL APPLICABILITY The present invention is intended to expose a mold type semiconductor device.
Instead of Ni plating, which was used to prevent oxidation of the Cu surface, etc., the following cost reduction effect is achieved by using Ag to replace Cu with Cu and using an organic film with a hydrophilic organic chain that binds to Ag. was gotten. (1) Processing time is significantly shortened compared to Ni plating.

Regarding the material cost, K [Ag (CN) ₂ ] is used, but considering that it is an amount of about ₂ to 5 g / l, and in the case of the Ni plating solution, it is necessary to renew the entire solution by increasing the phosphorus concentration. ,
There is no significant increase. (2) Phosphorus contained in the plating layer affected the solder wettability during Ni plating, but the solder wettability is improved by non-phosphorization and substitution Ag, and the solder voids are reduced, improving the yield. To do.

(3) When forming a solder film on the terminals,
Since it is not necessary to use the flux, the cleaning process can be omitted.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view of a lead frame surface after surface treatment in a manufacturing process according to the present invention.

2 is a conceptual cross-sectional view of the portion of FIG. 1 after die bonding.

FIG. 3 is a process diagram of lead frame processing in one embodiment of the present invention.

FIG. 4 is a process diagram of element assembly in one embodiment of the present invention.

[Explanation of symbols]

 1 Lead frame 2 Substituted Ag 3 Hydrophilic organic chain 4 Coating 5 Si chip 6 Solder

Claims (3)

[Claims] 1. A method of manufacturing a mold-type semiconductor element, comprising: fixing a semiconductor element body to a mount portion of a lead frame made of a copper-based material; exposing at least the tip of an external lead portion of the lead frame and sealing with a resin. A mold comprising a step of contacting the surface of the lead frame with water containing potassium potassium cyanide and a hydrophilic organic substance to form a surface film, and then fixing the semiconductor element body to the mount portion of the lead frame with solder. Manufacturing method of semiconductor device. 2. A step of connecting an external lead portion to an electrode on the surface of the semiconductor element body by bonding a conductor after the step of fixing the semiconductor element body, a step of applying a bonding coating resin on the surface of the semiconductor element body, and The method for manufacturing a mold-type semiconductor element according to claim 1, including a step of molding a sealing resin. 3. The method of manufacturing a mold type semiconductor device according to claim 1, further comprising the step of immersing the external lead portion exposed from the sealing resin in a solder bath.