JPS5843183B2 - How to solder two parts - Google Patents

Abstract

PURPOSE:To prevent soldering from becoming brittle by using solder grains or solder pieces coated with inert and insulating coil, with kinematic viscosity 10-100,000 cst, when a semiconductor pellet is fixed on a stem substrate. CONSTITUTION:Many solder balls 7 are put into insulating oil tank 9 filled with inert, insulating oil, with kinematic viscosity 10 to 100,000cst., and the surface of solder balls 7 is covered with insulating oil 8. On stem substrate 12, heated to 250- 350 deg.C by heater 11, which also functions as a heat discharge plate, solder balls are dropped by using an injector, and at the same time, the surface of molten solder 7' is covered with floating insulating oil 8'. In this way, the solder is prevented from becoming brittle. By using a supersonic oscillation horn, oil 8' and solder 7' are removed, and here semiconductor pellet 15 is mounted and cooled, and thereby pellet 15 and substrate 12 are bonded together. By this, soldering under a fixed specification can be rendered feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a soldering method for soldering and fixing a base material and an object to be attached, and in particular to a soldering method for soldering a semiconductor pellet as an object to be attached onto a substrate as a base material. The present invention relates to a method for manufacturing a pellet soldering structure in an apparatus.

Currently, in order to manufacture semiconductor devices such as transistors, a pellet mounting process is first performed.

This pellet mounting process generally uses the soldering method described below.

That is, as shown in FIG. 1, in order to solder the stem board 1 which also serves as a heat sink, solder pieces 2 are placed on a predetermined position a, and then they are led into a heating furnace and the solder pieces 2 are soldered. At the same time, the pellets 3 are fed while being slightly slid in order to melt them and to make them easily fit onto the melted solder 2'.

and soldering.

By the way, in this manufacturing method of the pellet mount process, thermal oxidation tends to occur when the solder piece 2 is heated, which deteriorates the life of the semiconductor device. Also, if the solder comes into contact with the outside air after the pellet mount structure is manufactured, it will oxidize. It also has drawbacks such as becoming brittle and causing thermal fatigue as a semiconductor device.

Therefore, in order to eliminate these drawbacks, conventionally, as shown in FIG. 2, the stem board 1 and the solder piece 2 are preheated in a heating furnace 4 with a preheater 5 at a low temperature (approximately 250°C or less), and then heated to a temperature of approximately 250°C to The solder piece 2 is melted using a high temperature heater 6 at 350°C to form the solder 2. At this time, the atmosphere is covered with a cover 7, and the cover 7 is filled with N2 gas as an inert gas to absorb the heat of the solder 2'. Efforts are made to prevent oxidation.

However, the technique of always completely filling the cover 7 with N2 gas is extremely difficult in practice, and thermal oxidation prevention has not been perfect.

Moreover, the above-mentioned method still has the problem that after the pellet mount structure is manufactured, it is necessary to separately adopt a mechanism to shut off the solder and the outside air, making it difficult to implement.

This invention has been proposed in consideration of the above circumstances, and involves coating the surface of ball-shaped solder grains or solder pieces with an inert insulating oil having a kinematic viscosity of 10 to 100,000 cst, and then It is characterized in that the object to be attached is placed and heated with the above-mentioned solder grains or solder pieces coated with insulating oil interposed therebetween.

A specific embodiment of the present invention will be described below with reference to the drawings.

First, before explaining the method for manufacturing the pellet structure, a specific example of the insulating oil that covers the surface of the solder grain or solder piece will be described in advance.

As a thin insulating oil, it has the characteristics shown in Table 1 below, and the molecular formula structure is (CH3)3 SiO-Xn-
8i(CH3)s (where X is (CH3)25iO,
n=1, 2, 3. -...-) (for example, Shin-Etsu Silicone Oil KF96 manufactured by Shin-Etsu Silicone Co., Ltd.).

Next, a method for manufacturing the pellet structure will be explained.

FIGS. 3 to 8 are cross-sectional views of process equipment and parts for explaining a method of manufacturing a pellet soldering structure according to an embodiment of the present invention.

Then, as shown in FIG. 3, ball-shaped solder grains 7, 7. ...is shown in Table 1 above and is inert and has a kinematic viscosity of 10 to 100,000est
into an insulating oil tank 8 containing insulating oil 8.

Next, as shown in Figure 4, a large number of injection needles 10°10.
It is adsorbed by a solder suction machine (not shown), etc. attached to the
It is placed on the heater 11 and dropped onto the stem substrate 12 which also serves as a heat sink.

Then, according to Table 1, insulating oil 8 has a specific gravity of 0.760 to 0.
．． 980, the solder grains 7, 7., which normally have a specific gravity of about 11.3. It is significantly smaller than...
As shown in FIG. 6, it immediately floats onto the melted solder T on the stem substrate 12 and covers its surface.

Thereafter, in accordance with a known technique, an ultrasonic vibration horn 13 shown in FIG. 7 is brought into contact with the insulating oil layer 8' and the molten solder 7' to push away the surface portions.

Further, as shown in FIG. 8, the pellet 15 that has been adsorbed on the collet 14 is placed on the surface portion.

At this time, the insulating oil layer 8' is heated by the heat of the molten solder T (approximately equal to the temperature of the heater 11), so as a result, a solder layer 7'' is formed as shown in FIG. At the same time, a pellet structure 16 is obtained in which an insulating oil coating layer 8'' is baked from the surface of the solder layer 7'' to the surface of the pellet 15.

In the above pellet structure manufacturing method, firstly, since the solder is always covered with insulating oil even before heating and melting, it is always covered with insulating oil when the solder is fixed (1), so it is prevented not only from thermal oxidation during heating and melting of the solder but also from oxidation (1) caused by outside air after the solder is fixed. do.

Secondly, the amount of insulating oil to be applied to the solder grains can be regulated to a predetermined amount because the surface tension is smaller than that of general oil and the thickness of the coating can be set to a precise level.

Furthermore, insulating oil has a low surface tension, so it exhibits anti-foaming properties and prevents bubbles from forming due to the generation of occluded gas or the entrainment of outside air, which is a problem when mounting objects on top of heated molten solder. Let it be discharged to the outside.

Thirdly, there is no need to provide a cover in the preheater or heating furnace or to provide a mechanism to isolate it from the outside air as in the conventional case.

In the above embodiment, the solder used was ball-shaped solder particles, but the present invention is not limited to this, and it is clear from the gist of the present invention that solder pieces finely cut into predetermined dimensions may be used, for example. It is.

Also, the means for applying insulating oil to solder particles or solder pieces is as follows:
There is no need to limit the method to immersion in an insulating oil bath as in the above embodiments, and spraying may be performed using a spray gun or the like.

According to this invention, the following excellent effects can be expected as a conclusion.

■ Since the insulating oil always covers the solder before and after it is fixed, oxidation of the solder is prevented and there is no risk of the solder becoming brittle.

■ A predetermined amount of insulating oil can be regulated, and soldering to a certain specification can be achieved.

■ Eliminates the need for preheaters and outside air cut-off mechanisms as in the past.
Automation of soldering work becomes easy.

■ Mass production work efficiency is greatly improved due to the above-mentioned ■ and ■.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a solder mounting stem board for explaining a conventional soldering method, Fig. 2 is a schematic sectional view of a solder heating furnace, and Figs. 3 to 9 are an embodiment of the present invention. FIG. 3 is a cross-sectional view of a solder mounting stem board coated with insulating oil in advance in each work step of the bullet soldering method for illustrating an example. 7.7. ......Solder grains, 8...-
... Insulating oil, 12 ... Base material (stem board), 1
5...Object to be attached (pellet).

Claims (1)

[Claims] 1 When soldering and fixing the object to the base material,
A method for soldering two components, which comprises placing an object to be attached with solder grains or solder pieces coated with an inert insulating oil having a kinematic viscosity of 10 to 100,000 cst in advance and heating the object.