JPH0637229A - Soldering method and jig for soldering - Google Patents

Abstract

PURPOSE:To provide a soldering method and a jig for soldering without producing any solder bridge during the step of preliminarily soldering an IC package of narrow lead pitch in relation to a soldering method and a jig for soldering CONSTITUTION:The title soldering jig 5 for holding an IC package 1 and performing the preliminary soldering step is to be composed of a claw sheet 5a no to be melted in a molten solder 3 externally pressing down and outer lead 2 of the IC package as well as an inner sheet not to be melted down in the molten solder 3 fitted to the outer lead 2 in contact with the inside thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering method and a soldering jig, and more particularly, to a method for presoldering outer leads of a flat type IC package and a jig for presoldering.

[0002] In recent years, further improvement in reliability has been demanded regarding the board mountability of the IC package and the mounting strength after the board is mounted. To meet such demands, pre-soldering processing is performed before mounting. The pre-soldering process refers to the process of forming a thin solder layer on the outer lead surface by dipping the lead in a molten solder bath.

When an IC package having gold-plated outer leads is mounted on a substrate, a mechanically brittle intermetallic compound of gold tin is generated at the mounting joint portion, resulting in a reduction in mounting strength.
In this case, if pre-soldering is performed on the gold plating of the outer leads in advance, some or almost all of the gold can be replaced with solder, and the intermetallic compound of gold tin after mounting can be generated. It is possible to prevent the deterioration of mounting strength.

[0004]

2. Description of the Related Art FIG. 4 is a cross-sectional view showing a conventional example of a pre-soldering process, in which (a) shows dipping and (b) shows pulling up.
Is an IC package, 2 is an outer lead, 3 is molten solder, 7
Represents a heat sink. In recent flat type IC packages, there are high density packaging packages in which the gap between adjacent outer leads is very narrow, and a heat sink for guiding the heat generated from the device to the outside is formed.

The conventional pre-soldering method uses the outer lead 2
Was immersed in the molten solder 3 and pulled up after a certain period of time. However, the outer lead pitch becomes smaller, and the gap between adjacent outer leads 2 is, for example, 0.3 mm.
When it becomes smaller, when the outer lead 2 is pulled up from the molten solder tank, the molten solder between the adjacent outer leads is not completely cut off and excess solder remains, solidifying in that state and forming a solder bridge, There is a problem that a short circuit occurs between the leads 2.

On the other hand, the immersion depth of the outer lead 2 into the molten solder 3 may be set strictly, but the outer lead 2 still causes variations in the solder creep-up height, and the soldering of the IC package may occur. The molten solder that has climbed up to the attachment pad part may cause a bridge between the pads.

Although measures such as increasing the temperature of the molten solder to lower the surface tension and lowering the pulling rate have been taken, this measure is added to the cost due to the reduction of the preliminary soldering capacity and adds to the semiconductor device. Problems such as reduced reliability due to increased thermal stress were unavoidable, and it was not a fundamental solution to complete solder breakage and avoid the formation of solder bridges.
Therefore, new measures are required.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the present invention performs pre-soldering without lowering processing capacity and without increasing thermal stress, and has an IC package with a narrow lead pitch. It is an object of the present invention to provide a soldering method and a soldering jig in which a solder bridge is not generated between the outer leads 2.

[0009]

FIG. 1 is a sectional view showing a first embodiment, FIG. 2 is a sectional view showing a second embodiment, and FIG. 3 is a sectional view showing a third embodiment.

The above problem is that when pre-soldering the outer leads 2 of the IC package 1, a plate 4 insoluble in the molten solder 3 is placed on the surface of the molten solder 3 in the molten solder tank 3a. The outer lead 2 is connected to the molten solder 3
It is solved by a soldering method in which the outer lead 2 is brought into contact with the end of the plate 4 and the molten solder 3 is squeezed to pull up the IC package 1 after the immersion.

A soldering jig for holding the IC package 1 and performing pre-soldering. The outer lead 2 of the IC package 1 is pressed from the outside and the molten solder 3 is held.
This is solved by a soldering jig having an insoluble nail plate 5.

A soldering jig for pre-soldering the IC package 1, said IC package 1
Holding the outer leads 2 of the IC package 1 from the outside, and mounting the nail plate 5 insoluble in the molten solder 3 and the inner plate 6 in contact with the inside of the outer leads 2 and insoluble in the molten solder 3.
It is solved by a soldering jig having and.

[0013]

In the present invention, when the outer lead 2 is pulled up from the molten solder 3, the outer lead 2 is brought into contact with the end of the plate 4 and the molten solder 3
Since the IC package 1 is pulled up while squeezing, excess solder residue does not occur on the outer leads 2, and as a result, it is possible to prevent the formation of solder bridges between the adjacent outer leads 2.

If a soldering jig having a nail plate for pressing the outer lead 2 of the IC package 1 from the outside and having an insoluble nail plate 5 in the molten solder 3, the molten solder 3 is restricted by the nail plate 5. Therefore, when the IC package 1 is pulled up, the amount of solder remaining on the outer leads 2 is limited,
As a result, the occurrence of solder bridges between adjacent outer leads 2 is limited.

In addition to the claw plate 5, the outer lead 2
If the inner plate 6 that is insoluble in the molten solder 3 is attached to the inside of the IC, the molten solder 3 is limited to the lower part of the outer lead 2 and does not wrap around to the upper part of the outer lead 2.
After pulling up the package 1, almost no solder bridge is generated between the adjacent outer leads 2.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing a first embodiment.
Is an IC package, 2 is an outer lead, 3 is molten solder, 3a
Is a molten solder bath, 4 is a ceramic plate, and 7 is a heat sink. The IC package 1 is, for example, a flat type IC package having gold-plated outer leads on four sides, the gap between adjacent outer leads 2 is, for example, 0.28 mm, and, for example, 41 outer leads are arranged on each side. ing.

The ceramic plate 4 which is in contact with the surface of the molten solder 3 and has one end exposed on the molten solder 3 is placed in the molten solder bath 3a.
Attach to. The ceramic plate 4 is insoluble in the molten solder 3 and contacts all the outer leads 2 arranged side by side.

The main surface of the IC package 1 is inclined to the surface of the molten solder 3 and the outer leads 2 are immersed in the molten solder 3.
The immersion depth should include at least the mounting portion of the outer lead 2 on the printed circuit board. The temperature of the molten solder 3 is, for example, 250 to 300 ° C., and after dipping for 5 to 7 seconds, the outer leads 2 are brought into contact with the ends of the plate 4 and the molten solder 3 is squeezed and pulled up in an oblique direction. Although this work may be performed manually, it can be performed with reliability by setting the inclination angle of the main surface of the IC package 1 to be 45 ° and the pull-up direction to be 45 ° by the robot mechanism.

In this way, it was possible to pull up the outer lead 2 without causing excess solder residue.
As a result, the occurrence of solder bridges between the adjacent outer leads 2 was drastically reduced compared to the conventional example in which the plate 4 was not installed.

FIG. 2 is a sectional view showing a second embodiment, the reference numerals are the same as those in FIG. 1, and 5 is a solder dipping jig and 5a.
Is a nail plate and 8 is a flux. The solder dipping jig 5 holds the IC package 1 and holds the outer lead 2 with the molten solder 3
It has a claw plate 5a that presses the outer lead 2 from the outside at the tip. The claw plate 5a is made of a material having impurities in the molten solder 3 and is made of, for example, titanium.

The IC package 1 is attached to the solder dipping jig 5, and the claw plate 5a is brought into contact with the outside of the outer lead 2. After that, the outer lead 2 and the claw plate 5a are soaked in a flux 8 of molten pine or the like so that the outer lead 2 and the claw plate 5a are sufficiently dipped, and then the main surface of the IC package 1 is inclined with respect to the surface of the molten solder 3 to fix the outer lead 2 Immerse in the molten solder 3. The flux 8 flows and collects on the claw plate 5a. Since the flux 8 decomposes in the molten solder 3 and the active ingredient that improves the solder wettability gradually disappears, the larger the amount of the flux 8 that accumulates on the nail plate 5a, the better the flow of the solder. This is advantageous for suppressing the occurrence of bridges.

The temperature of the molten solder 3 is, for example, 250 to 300 ° C.
Then, after soaking for 5 to 7 seconds, the outer lead 2 is pulled up.
The direction of pulling up is not necessarily diagonal. In this way, the outer lead 2 could be pulled up without excessive solder residue. As a result, almost no solder bridge was formed between the adjacent outer leads 2.

FIG. 3 is a cross-sectional view showing a third embodiment. Reference numerals are the same as those in FIG. 2, 6 is a ceramic plate, and 9 is a magnet. In this example, in addition to the second embodiment, a ceramic plate 6 contacting the inside of the outer lead 2 is arranged.
The ceramic plate 6 is fixed by the magnet 9 by using the attraction force with the magnetic plate in the IC package 1.

In the third embodiment, the molten solder 3 is completely prevented from wrapping around the inner side of the outer lead 2, the molten solder 3 does not creep up, and a solder bridge is not generated between the adjacent outer leads 2. I couldn't see it at all.

[0025]

As described above, according to the present invention,
In the pre-soldering of an IC package with a narrow lead pitch, the effect of suppressing the generation of solder bridges is exerted, and the creeping height of the outer lead 2 of the solder varies, and the thermal stress of the IC package due to the temperature rise of the molten solder. Conventional problems such as increase of

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment.

FIG. 2 is a sectional view showing a second embodiment.

FIG. 3 is a sectional view showing a third embodiment.

FIG. 4 is a cross-sectional view showing a conventional example, in which (a) shows the time of immersion and (b) shows the time of pulling.

[Explanation of symbols]

 1 is an IC package 2 is an outer lead 3 is molten solder 3a is molten solder bath 4 is a plate, ceramic plate 5 is a solder dipping jig 5a is a claw plate 6 is a plate, ceramic plate 7 is a heat sink 8 is a flux 9 is a magnet

Claims (3)

[Claims] 1. When pre-soldering the outer leads (2) of the IC package (1), a plate (4) which is insoluble in the molten solder (3) is formed on the surface of the molten solder (3) in the molten solder bath (3a). ) Is installed, and the outer leads (2) of the IC package (1) are connected to the molten solder.
After immersing in the (3), the outer leads (2) are brought into contact with the edges of the plate (4) and the molten solder (3) is squeezed, and the IC package is
(1) A soldering method characterized by pulling up. 2. A soldering jig for holding an IC package (1) and performing pre-soldering, wherein an outer lead (2) of the IC package (1) is pressed from the outside to melt the solder.
(3) A soldering jig having an insoluble claw plate (5). 3. A soldering jig for pre-soldering an IC package (1), the IC package (1)
Holding the outer leads (2) of the IC package (1) from the outside, and mounting the nail plate (5) insoluble in the molten solder (3) and the inside of the outer leads (2), A soldering jig comprising a molten solder (3) and an insoluble inner plate (6).