JPS5935180B2 - IC lead joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved IC lead joining method for joining a lead terminal to the end of a thin film conductor deposited on a ceramic substrate for IC.

Conventionally, methods for joining IC leads include a method using a so-called clad lead frame in which a band-shaped brazing material is pressure-welded to the clad, and a method of directly heating and joining an ordinary lead frame with a brazing material.

In the former case, first, a base conductor for a lead frame to which a band-shaped brazing material such as Ag material (71 to 73% Ag, the rest is Cu alloy) is crimped to the cladding is punched out for the IC lead frame, and the cladding material is cut out. Form a lead frame.

Subsequently, the brazing material portion of this clad lead frame is superimposed on the end portion of the thin film conductor formed by vapor deposition on the ceramic substrate and bonded by heating. According to this method, the cost of punching out the base conductor for the lead frame is increased, and only a portion of the brazing material that is crimped to the base conductor in the form of a band is used for the lead frame.
The other 10 parts are not punched and are discarded.

Therefore, expensive brazing material such as Ag material is discarded without being punched, which is very uneconomical. Furthermore, the joint between the brazing material and the base conductor, which is crimped with the cladding, has drawbacks unique to cladding crimping. That is, since the thickness and width of the band-shaped brazing material that has been cradled and crimped are uneven,
If the thickness and width of the brazing material strip is made narrow in order to save the soldering material, the brazing material strip will meander and be pressure-bonded to the base conductor. Therefore, in order to use a clad material frame as a lead frame for an IC, it is necessary to crimp a wide and thick band of brazing material onto the cladding, which requires a large amount of expensive brazing material, which is very expensive. It is uneconomical. Furthermore,
At the joint between the band-shaped solder metal and the base conductor, the solder metal permeates into the base conductor between grains, and therefore, when the lead is heated and bonded to the end of the thin film conductor on the ceramic, the solder metal penetrates into the base conductor due to this intergranular penetration. Cracks are likely to occur.

Therefore, poor contact of the C lead is likely to occur, resulting in failure of the IC. The latter method of directly heat-bonding the lead frame to the thin film conductor on the ceramic substrate using a brazing material is as follows.

That is, a band-shaped brazing material is stacked on the ends of the lead group of the lead frame, and both ends are spot-fixed.

Next, the end portions of a series of thin film conductors deposited on the ceramic substrate are brought into contact with this band-shaped brazing material, and in this state, the end portions of each lead and the end portions of the thin film conductors are respectively heated and bonded. During this heating bonding, the brazing material disposed between the leads is heated and melted, and moved to the respective adjacent lead ends by the action of surface tension. Therefore, each thin film conductor end and each lead end are joined with each lead being disconnected from each other. However, when the leads are joined by this method, the solder material placed between the leads is not sufficiently melted, and a defective product may be manufactured in which the leads are connected to each other by the solder material.

This is the most fundamental drawback, causing electrical shot and fatal damage to the C-chip. Furthermore, since an unnecessary amount of brazing material is disposed between the leads, it is very uneconomical, and the amount of brazing material attached to each lead is uneven. Furthermore, since the work process is complicated, it is difficult to mechanize and automatically attach the leads. SUMMARY OF THE INVENTION An object of the present invention is to provide an IC lead bonding method having the following advantages in view of the conventional IC lead bonding method having the above-mentioned drawbacks.

(a) Eliminate wasteful consumption of expensive brazing material, join each 1C lead with the minimum necessary brazing material, and make the amount of brazing material attached to each lead uniform.

(b) To reliably join each 1C lead without causing any joining between the lead terminals that would cause electrical shorts.

(c) Simplify the IC lead bonding process so that it can be easily mechanized.

That is, according to the present invention, a convex portion or a concave portion is formed on the surface of each lead end of an IC lead frame, and a minimum amount of brazing material necessary for joining the leads is crimped onto the convex portion or concave portion. Ru.

Next, the IC ceramic substrate is brought into contact with the lead frame to which the brazing material is crimped, and the ends of each lead and the ends of the conductor formed by vapor deposition on the ceramic substrate are directly heated and bonded. The present invention will be described in more detail below with reference to embodiments shown in the accompanying drawings.

1 is a plan view of an IC lead frame 1 used in the present invention, and FIG. 2 shows an end of the lead 3 of the IC lead frame 1 shown in FIG. It is an enlarged view when seen from the direction.

That is, as is clear from FIG. 2, a relatively thin concave groove 4 is formed at the end of the lead 3, and a brazing material 5 is crimped so as to surround this groove 4. There is.

The brazing material 5 is inserted into the groove 5 formed at the end of the lead 3 as shown in the figure.
It firmly bites into the inside and is securely fixed. Next, the IC lead frame 1 to which the brazing material 5 is crimped is placed in a third
As shown in the figure, a large number of thin film conductors 11, some of which are shown in the figure.
The thin film conductors 11 are superimposed on the IC ceramic substrate 7 on which the conductors are deposited by vapor deposition, so that the ends of each lead and the ends of each thin film conductor 11 are aligned with each other.

Here, the other end of each thin film conductor 11 is connected to an IC chip 9, respectively. Next, in this state, each lead end is heated to melt the solder material 5 that has been crimped and cooled to perform joining.

Furthermore, each lead 3 is cut at the position shown by dotted line B in FIG. 1 to form IC leads 3 arranged as shown in FIG. 4. In the above description, the formation I having the concave groove 4 is
Although the C lead frame has been described, the present invention is not limited to this, and grooves or protrusions of any shape may be used.

For example, as shown in FIG. 5, a groove 13 having a triangular cross section may be formed at the end of each lead, or a triangular protrusion 15 may be formed as shown in FIG. According to this invention, since the minimum necessary amount of brazing material is crimped through the grooves and protrusions provided at the ends of each lead, the brazing material can be securely fixed without being wasted unnecessarily.

Furthermore, since it is mechanically easy to maintain a constant pressure applied to each lead end during crimping, the ends of each lead 3 will not become uneven in the vertical direction. Furthermore, there is no risk that the ends of the leads will be joined to each other, and the leads can be reliably joined to the ends of the vapor-deposited conductor of the ceramic substrate for IC. or,
This invention has the advantage that since the working process is simple, it can be easily automated with simple equipment and the processing cost is very low.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a lead frame for IC used in the present invention, FIG. 2 is an enlarged view of the essential parts of FIG. 1, and FIG. 3 is a plan view showing an example of a ceramic substrate for IC. FIG. 4 is a plan view showing a state in which leads are attached to a ceramic substrate, and FIGS. 5 and 6 are enlarged views of essential parts of the IC lead frame. 1...Lead frame for IC, 3...
Lead, 4, 13...groove, 15...protrusion, 5...brazing material, 7...ceramic substrate, 9...IC Chip... Vapor deposited thin film conductor.

Claims (1)

[Claims] 1. When joining the lead 3 to the end of the conductor 11 formed by vapor deposition to form a wiring on the ceramic substrate 7,
The brazing material 5 is crimped onto the grooves and protrusions 4, 13, and 15 provided at the ends of the leads 3 of the lead frame 1, and then the ends of the leads and the ends of the conductor 11 are overlapped and heated and bonded.
C lead joining method.