JPS5843182B2 - How to solder two parts - Google Patents

Abstract

PURPOSE:To prevent oxidation to solder layer by forming inert insulation oil coating layer of the specific dynamic viscosity on the solder layer surface. CONSTITUTION:A substrate 8 is led onto a heater 12 and is heated. Next, insulating oil 10' is thinly coated by a desired amount on the surface to be soldered of the substrate 8. The specified amount of solder piece 9' is placed on the insulating oil 10'. This results in that the insulating oil layer 10'' covers the surface of molten solder 9''. Next, an ultrasonic vibrating horn 13 is contacted down to the insulating oil layer 10'' and molten solder 9'' to push away the surface part. The pellet 11 having beforehand been attracted on a collet 14 is placed on the molten solder 9''. In this case, the insulating oil layer 10'' is covered up to the top surface of the pellet 11. At this time, the insulating oil layer 10'' is heated by the heat of the molten solder 9'' and therefore the solder layer 9 is formed and at the same time, the insulating oil coating layer which is inert and whose dynamic viscosity is 10-100,000cst is formed from the solder layer 9 surface up to the surface of the pellet 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for soldering a base material and an object to be attached, and in particular to a method for soldering a semiconductor pellet as an object to be attached to a substrate as a base material that also serves as a heat sink. Soldering suitable for the manufacturing method is related to the method, and its main purpose is to prevent oxidation of the solder layer in the pellet mounting process.

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

This pellet mounting process is a process in which pellets are generally soldered and fixed onto a board that also serves as a heat sink, and
They often perform tasks such as the following:

That is, as shown in FIG. 1, first, solder pieces 2 of the board 1 are placed on a predetermined position a, and then they are introduced into a heating furnace to melt the solder pieces 2. , the pellet 3 is supplied onto the molten solder 2' while being slightly slid to make it easier to solder.

By the way, regarding this pellet mount, it is necessary to prevent thermal oxidation of the solder in order to prevent it from deteriorating the life span of a semiconductor device that has been manufactured by being stuck.

Therefore, conventionally, as shown in FIG. 2, the heating furnace 4 is
The board 1 and the solder piece 2 are preheated by a preheater 5 at a low temperature (approximately 250°C or less), and then the solder piece 2 is melted by a heater 6 at a high temperature of 250°C to 350°C to form solder 2'.

At this time, the surrounding area is covered with a cover 7, and the inside of the cover 7 is filled with N2 gas as an inert gas to prevent thermal oxidation of the solder 2.

However, in reality, the technique of completely filling the cover 7 with N2 gas is extremely difficult.

Moreover, when attempting to automate the pellet mounting process, it is necessary to adopt a mechanism that isolates it from the outside air, which has the drawback of making it even more difficult to prevent thermal oxidation of the solder.

This invention is proposed for the purpose of eliminating the above-mentioned drawbacks, and therefore includes the step of applying an inert insulating oil having a kinematic viscosity of 10 to 10,000 ocst to the fixed surface of a substrate as a base material, and the step of applying an insulating oil having a kinematic viscosity of 10 to 10,000 ocst, and heating the base material. A soldering method is provided which includes the steps of supplying and melting solder to the fixing surface of the solder, and supplying and soldering an object to be attached onto the molten solder.

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

FIG. 3 shows the pellet mount structure of a semiconductor device obtained by carrying out the present invention upon completion of the pellet mounting process, in which 8 is a stem substrate that also serves as a heat sink, 9 is a PB solder layer, and 10 is a solder layer 9. Inert with an insulating coating from the surface to the upper surface of the pellet 11 and having a kinematic viscosity of 10 to I 0000
0 cst insulating oil coating layer.

The specific material for this insulating oil coating layer 10 has the following characteristics as shown in Table 1, and has a molecular formula structure of (CH3
)3SiO-Xn-8iCCHa)3 (where X is (CH
3) 2SiO with n=1, 2, 3,...
) chain dimethylpolysiloxane (for example, Shin-Etsu Silicone Oil K manufactured by Shin-Etsu Silicone Co., Ltd.)
There is something called F96).

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

1. First, as shown in FIG. 4, the stem substrate 8 is guided onto the heater 12 and heated to 250 to 350° C. (high temperature state).

Next, a desired amount of insulating oil 10' is applied thinly to the soldering surface of the stem board 8.

Then, as shown in FIG. 5, a predetermined amount of solder piece 9' is placed on the insulating oil 10'.

At this time, the specific gravity of the solder piece 9' is approximately 11.3, while the specific gravity of the insulating oil 10' is 0.760 as shown in Table 1.
~0.980, and the surface tension is small, so as shown in FIG.
0'' will cover it.

Then, as shown in FIG. 7, the ultrasonic vibration horn 13 is brought into contact with the insulating oil layer 10'' and the stored solder 9''1, and the surface portion is pushed away.

Furthermore, as shown in FIG. 8, the pellet 11 that has been adsorbed on the collet 14 is placed on the molten solder 9''.

In this case, an insulating oil layer 10 is formed on the upper surface 1 of the pellet 11.
” is covered.

At this time, the insulating oil layer 10'' is heated by the heat of the molten solder r (approximately equal to the temperature of the heater 12), so as a result, as shown in FIG. 9
are formed, and pellets 11 are formed from the surface of the solder layer 9.
An insulating oil coating layer 10 is formed over the surface.

It should be noted that the other steps of this semiconductor device are carried out by conventionally known working methods, and therefore their explanations will be omitted.

In the soldering method described above, the surface of the heated and melted solder 9'' is covered with an insulating oil layer 10' during pellet mounting, so thermal oxidation is prevented. Since the insulating oil layer 10 covers the entire surface of the solder layer 9, the solder layer 9 is prevented from being oxidized by the outside air and becoming brittle.

In addition, since the insulating oil 10' has a small surface tension, it will not be left behind in the heated and molten solder 9'', and has strong antifoaming properties, so it will not draw in outside air or cause the solder pieces 9' Even if the stored gas contained inside is generated, it is immediately discharged to the outside.

According to this invention, the following advantages can be expected.

(2) The solder layer is prevented from thermal oxidation during the work of fixing the object to the base material, and after being fixed, it is isolated from the outside air, so oxidation by the outside air is prevented.

(2) Since no air bubbles or gas bubbles remain in the solder layer, the solder layer does not deteriorate over time, and the life of a button on a semiconductor device is significantly prevented from deteriorating.

(2) Especially in semiconductor devices, the solder layer is protected by an insulating oil coating layer, so even if moisture intrudes from the outside, moisture resistance is improved.

(2) Furthermore, especially in semiconductor devices, since the pellet surface is protected, the Pn junction surface is not contaminated during the manufacturing process, and the hFE characteristics of transistors and the like that perform an amplification function are also improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a soldering board showing the mounting process of a conventional soldering structure, Fig. 2 is a schematic sectional view of a conventional heating furnace, and Fig. 3 is a sectional view of a soldering structure according to the present invention. , and FIGS. 4 to 8 are cross-sectional views of the solder-mounted and insulating oil-coated substrates in each work step for explaining the manufacturing method according to the present invention. 8...Substrate (base material), 9...Solder layer,
10...Insulating oil coating layer, 10'-...Insulating oil, g (mounted object), b...Fixing surface. 11...Peretz

Claims (1)

[Claims] 1. When soldering and fixing the object to be attached to the base material, first apply an inert material to the fixing surface of the base material with a kinematic viscosity of 10 to 100.
000 cst of insulating oil, a step of supplying solder to the fixed surface of the heated base material and melting it, and a step of supplying the object to be attached onto the molten solder and soldering it. Soldering two parts is a method.