JPH0982830A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop the method of soldering a package lead wherein no oxide film is formed on the solder surface in the solder dipping step having excellent wettability of the lead with solder while leaving no residual solder at all. SOLUTION: The solder dipping step of a package lead using a flux vessel and a solder vessel includes the four steps mentioned as follows, i.e., the first step of coating a lead with a flux of chlorine base compound in the first flux vessel 1, next the second step of dipping the lead in the first jet type soldering vessel 3 and the third step of coating the lead with high viscous resin base flux in the second flux vessel 4 and the fourth step of dipping the lead in the second stationary solder vessel 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for solder dipping (immersing) a lead pin of a semiconductor package, particularly a PGA ceramic package.

[0002] In recent semiconductor packages, the number of leads has been increased with the increase in the density and integration of semiconductor elements, and the pin grid array (PGA) method has been widely used.
The pitch of the lead pins is becoming narrower, and it is necessary to develop suitable soldering technology.

[0003]

2. Description of the Related Art FIG. 4 is an explanatory view of a conventional example. In the figure, 11 is a PGA package, 12 is a lead pin, 15 is a solder (crosslink residue), and 16 is a solder (icicle residue).

Conventionally, solder dipping for mounting on a printed board is performed after the sealing process of a pin grid array (PGA) ceramic package 11 as shown in FIG. 4A is completed.
Recently, the spacing between the lead pins 12 of PGA has become narrower from 100 mil to 50 mil as the density of devices has been increased.
In addition, the pin array has a staggered 100 mil pattern.

[0005]

Therefore, in the conventional dipping method in the solder dipping process, a short circuit due to the bridging residue 15 of the solder between the lead pins 12 as shown in FIG. 4B is likely to occur. Also, in jet type soldering, an oxide film of solder is generated as a slag, which may adhere to the product,
There was a problem that solder replenishment was required and running cost was high. In addition, as shown in FIG.
An oxide film is formed on the solder surface during solder dipping, and this is the icicle residue of the solder at the tip of the lead pin 12 during dipping.
It hung down as 16 and caused a defect. Therefore, in the solder dipping process, it is necessary to perform solder dipping in a state where an oxide film is difficult to form.

Further, in the conventional PGA, the ceramic portion on the lead side is pressed to perform the solder dipping, but the distance from the edge of the PGA package 11 to the lead pin 12 is becoming narrower in order to increase the mounting density. The problem of fixation of has also occurred.

In view of the above points, the present invention is provided for the purpose of obtaining a method in which an oxide film is not formed on the solder surface at the time of solder dipping, solder wettability is good, and no solder slag remains.

[0008]

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, 1 is a first flux tank, 2 is a heating tank, 3 is a first solder tank (jet type), 4 is a second flux tank, and 5 is a second solder tank (static type).

In the present invention, as shown in the principle explanatory diagram of FIG. 1, the PGA is made in a state where it is difficult to form an oxide film in the soldering process.
In order to cope with fine pitch by soldering, the two kinds of flux are used to prevent oxidation of the solder surface and prevent solder residue from remaining on the lead pins.

First, regarding the flux, two kinds of flux are properly used according to the purpose, and first, the chlorine (Cl) type flux is used to remove the lead oxide film in the assembly process before the solder dipping of the lead. After preheating, the lead pins were well wetted with the jet type first solder, and then the fine pin pitch pins were made stationary by using a flux composed of high-viscosity rosin for fine pitch. Gently dip into the first solder bath to prevent solder shorts and sagging.

Further, with respect to oxidation of the solder surface by heating, contact of the solder surface with air is prevented, and formation of an oxide film is prevented. Therefore, as shown in FIG. 2 (a), the surface of the solder is covered with an inert gas such as nitrogen and oxygen (air) is used.
To prevent the solder surface from being oxidized by contact with
As shown in (b), the solder surfaces of the first and second solder baths are covered with a flux 10 to prevent oxidation of the solder.

Furthermore, regarding the method of holding the package,
As shown in FIG. 3, a plurality of magnets are attached to the holding plate of the package, the metal cap portion on the front surface of the package is adsorbed, and the lead pins on the back surface are dipped in the solder bath to cover the lead pin surfaces with solder. At that time, the magnet 13 is attached to the package holding plate 14 so as not to hit the seal ring portion of the cap.

That is, as shown in FIG. 1, the object of the present invention is to use a flux bath and a solder bath for solder dipping of the leads of a package. A step of applying a flux, a step of subsequently dipping the lead in a jet type first solder bath 3, and a step of applying a high viscosity rosin-based flux to the lead in a second flux bath 4; And then dipping the leads into the stationary second solder bath 5,
By bubbling nitrogen gas into the first and second solder baths, and by performing a solder dip by covering a part or the entire surface of the first and second solder baths with flux, This is achieved by soldering one or more of the packages with a magnet.

The above-mentioned solder dipping work is carried out by setting the package in a fixed area provided with a magnet as shown in FIG. That is, the package body is floated from the fixing jig by using a guide so that the seam weld cap or the like does not directly hit the jig.

[0015]

1 to 3 are explanatory views of the principle and a schematic cross-sectional view of an embodiment of the present invention. In the figure, 1 is the first
Flux tank, 2 heating tank, 3 first solder tank (jet type), 4 second flux tank, 5 second solder tank (static type), 6 solder tank, 7 molten solder , 8 is a bubbling device, 9 is nitrogen (N ₂ ) gas, 10 is flux,
11 is a PGA package, 12 is a lead pin, 13 is a magnet, and 14 is a package holding plate.

Pin system 0.46φ, pitch 2.54mm,
One embodiment of the present invention using a RIT135 type PGA package having an outer shape of 35.56 mm square will be described with reference to FIGS. The lead pins are packaged by coating the Kovar lead pins 12 with Ni plating to a thickness of 2 to 4 μm, and then applying A
u plating is performed to a thickness of 1 to 5 μm.

As shown in FIG. 1, first, a flux is applied to the lead pins 12 using an inorganic flux in the first flux tank 1. This flux is a combination of an inorganic acid and an inorganic salt. Typically, zinc chloride or ammonium chloride removes an oxide film on the surface due to a heat history of a die bonder, a wire bonder or the like by a strong activating action. This makes it possible to omit the return process in advance. In addition, an organic acid-based water-soluble flux or the like can also be used.

Next, although not shown, when a water-soluble flux is used, a washing tank may be provided between the first flux tank 1 and the heating tank 2 to wash the water-soluble flux. Next, dip the lead pins 12 into the first solder bath 3 equipped with a bubbling device as shown in FIG.
Jet soldering is performed at 40 ° C. for 5 to 10 seconds. This bubbling device 8 has porous ceramics or superhard metal installed in the lower part of the tank and is supplied with nitrogen (N ₂ ) gas 9 from the outside to measure the oxidation prevention of the solder surface. This has an advantage over the gas external supply method that it is not affected by the generation of gas during solder dipping.

After that, a rosin-based synthetic resin having a particularly high viscosity, for example, a solvent # 7200A made by Senju Metal Co., Ltd. having a specific gravity of 1 or more is used in the second flux tank 4 and attached to the lead pin 12 at the time of pulling. This enables good soldering without an oxide film.

Finally, it is placed in the second solder bath 5 and immersed in stationary solder at 240 ° C. for 5 to 10 seconds.
As shown in (b), the portion other than the solder dip surface that is exposed to the air is melted with the flux 10
Cover the solder surface of to prevent the generation of solder slag.

The above-mentioned solder dipping work is carried out by setting the PGA package 11 on the package holding plate 14 of the fixing jig having the magnet 13 as shown in FIG. That is, the seam weld cap or the like is directly attached to the package holding plate 14
Use the guide to avoid hitting the PGA package 11
From the package holding plate 14.

[0022]

As described above, according to the present invention,
Two kinds of flux are used to prevent oxidation of the solder surface and prevent solder residue on the lead pins. Since a magnet is attached and the metal cap portion on the surface of the package is adsorbed and the lead pins on the back surface are dipped in the solder bath to cover the lead pin surface with solder, a large number of packages can be processed at the same time.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention (No. 1)

FIG. 3 is an explanatory diagram of an embodiment of the present invention (No. 2)

FIG. 4 is an explanatory view of a conventional example.

[Explanation of symbols]

In the figure, 1 first flux tank 2 heating tank 3 first solder tank (jet type) 4 second flux tank 5 second solder tank (static type) 6 solder tank 7 molten solder 8 bubbling device 9 N ₂ gas 10 Flux 11 PGA package 12 Lead pin 13 Magnet 14 Package holding plate

Claims (4)

[Claims] 1. A step of applying a flux of a chlorine-based compound to the leads in a first flux tank when solder dipping the leads of a package using the flux tank and a solder tank, and then a jet type first step. A step of dipping the lead in a solder bath, a step of applying a high-viscosity rosin-based flux to the lead in a second flux bath, and a step of dipping the lead in a static second solder bath; A method of manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein nitrogen gas is bubbled into the first and second solder baths. 3. The method for manufacturing a semiconductor device according to claim 1, wherein a part or the whole of the surfaces of the first and second solder baths are covered with flux to perform the solder dipping. 4. The method for manufacturing a semiconductor device according to claim 1, wherein one or more of the packages are attracted and held by a magnet to perform solder dipping.