JPH04130760A - Semiconductor chip carrier - Google Patents

Abstract

PURPOSE:To increase the junction strength of the conductive pattern of a printed-wiring board and an external connecting terminal while lessening the dispersion thereof by a method wherein a recession for a solder well is formed on the junction surface of the external connecting terminal. CONSTITUTION:Within an external connecting terminal 21, a trench 25 for a solder well is formed on the part near the printed wiring board 1 periphery of a junction surface 21a while the trench 25 is in the width W 1-5 times of the thickness (t) of the external connecting terminal 21 and in the depth D1/3-1/2 times of the thickness (t). At this time, the trench 25 is formed extending over the whole width of the external connecting terminal 21. In such a constitution, within the junction part of the conductive pattern 3 of the printed wiring board 1, the junction part in sufficient solder thickness and even length can be stably secured so that the junction strength may sufficiently be increased while lessening the dispersion thereof.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to semiconductor chip carriers.

[Conventional technology]

As shown in FIG. 4, the semiconductor chip carrier includes a printed wiring board 1 on which a conductive pattern 3 is formed around a chip mounting surface 1a, and external connection terminals 2.・One end is soldered to each conductive turn 3 . The other end of each external connection terminal 2 is connected by one metal ring 5.

This semiconductor chip carrier is used as follows.

As shown in FIG. 5, a semiconductor chip 10 is mounted on the chip mounting surface 1a, and the semiconductor chip 10 and the conductive pattern 3 are
After connecting them with wires 11, a resin sealing film 12 for protecting the semiconductor chip is formed. Next, place the semiconductor chip carrier A on the motherboard B, and connect the external connection terminal 2.
. . . The other side and the conductive pattern (not shown) of the motherboard B are connected by soldering (secondary mounting).

The external connection terminals 2 include external connection terminals 25 with a constant thickness as shown in FIG. 6, as well as external connection terminals 25 with a constant thickness as shown in FIG.
There is an external connection terminal 26 with a thick joint portion proposed in the applicant's previous application (Japanese Patent Application No. 1-278031).

[Problem to be solved by the invention]

In the case of the semiconductor chip carrier shown in FIG. 6.7, there is a problem that the solder joint between the conductive pattern 3 and the external connection terminals 25 and 26 is not sufficient.

When the bonding strength between the conductive pattern and the external connection terminal was investigated using the peeling method shown in FIG. 8, it was found that the bonding strength was not sufficient and had large variations. 30 is a clamping claw. In the case of the external connection terminal 26, there is a solder portion on the rear end surface of the convex portion, so this is somewhat better, but since this solder portion is not formed stably, it is not an essential solution.

If a semiconductor chip carrier is subjected to a reliability test (for example, a temperature cycle test) and then the bonding strength between the conductive pattern and the external connection terminal is examined in the same manner, the bonding strength may be extremely reduced in some carriers.

The reason why the solder joint is not sufficient is that there is a large variation in the thickness of the solder between the terminal joint surface and the conductive pattern surface, ranging from 2 to 50 mm. Particularly, if the solder thickness is thin on the peripheral edge side of the printed wiring board at the joint location, the joint strength seems to drop significantly.

In view of the above circumstances, it is an object of the present invention to provide a semiconductor chip carrier in which the bonding strength between a conductive pattern of a printed wiring board and an external connection terminal is sufficiently high (with little variation).

[Means to solve the problem]

In order to solve the above problem, the invention according to claim 1 includes a printed wiring board on which a conductive pattern is formed around a chip mounting surface and an external connection terminal, and the external connection terminal is soldered to the conductive pattern. In this semiconductor chip carrier, a concave portion for a solder pool is formed on the bonding surface of the external connection terminal.

There are various aspects regarding the formation position and shape of the recess. Regarding the formation position, it is preferable that it be close to the periphery of the printed wiring board, and regarding the shape, for example, as shown in FIG. 1, it is a groove 21 formed over the entire width of the external connection terminal 21. is preferred. Specifically, for example, as in claim 2, the recess for the solder pool is a groove formed in the width direction at a position on the peripheral edge side of the printed wiring board of the bonding surface, and the groove is a groove for forming an external connection terminal. Examples include those having a width of 1 to 5 times the thickness t and a depth of 1/3 to 1/2 of the external connection terminal thickness t.

Hereinafter, the semiconductor chip carrier of the present invention will be explained in more detail.

As shown in FIG. 4, the semiconductor chip carrier according to the present invention includes a printed wiring board 1 and a large number of external connection terminals 2.
It is equipped with... The printed wiring board 1 has a chip mounting surface (cavity portion) la in the center, and a large number of Cu conductive patterns 3 are formed around the chip mounting surface. One end of each external connection terminal 2 is soldered to each conductive pattern 3. The other ends of each external connection terminal 2 are connected by one metal ring 5. Of course, the other ends of each external connection terminal 2 may not be connected by the metal ring, but may be separated individually.

The chip mounting surface 1a is usually a concave surface or a flat surface.

The base material of the printed wiring board 10 is not limited to being entirely made of an insulating material, and may be a material having an insulating layer provided on the surface of a metal material.

The external connection terminal 2 is usually a plate with a thickness of about 0.15 to 0.35mm, and is made of 4270I (42% Ni).
, Fe balance), Cu alloy, etc.

Solder joints may melt or melt when heated during the secondary mounting stage.
To avoid damage, it is desirable to use high temperature solder with a solidus temperature of 280° C. or higher. For example, S n 3
．． 5%, Ag 1.5%, Pb 95% high temperature solder or Sn 5.0%, Ag 2.5%, Pb 92.5%
Examples include high-temperature solder. In addition, the solidus temperature is 1
It is also possible to use eutectic solder at 83°C or solder whose solidus temperature is at the level of 220 to 260°C. The solder used is usually cream solder.

When performing solder joints, conductive patterns 3 are printed using cream solder using a screen printing method using a metal mask, etc.
The bonding surfaces of the external connection terminals 2 are placed together and heated to be bonded and fixed. Note that the external connection terminal 2 is subjected to surface treatment using solder or the like in advance. Heating is done using a light beam (xenon lamp), YAG laser,
This is done using a near-infrared lamp, etc.

Next, the specific structure around the joint portion of the external connection terminal and the conductive pattern in the present invention will be explained with reference to FIGS. 1 to 3.

In the case of FIG. 1(a), the external connection terminal 21 is connected to the joint surface 21a.
Groove 2 for solder pool near the periphery of the printed wiring board.
5 is formed, and the groove 25 has an external connection terminal thickness t.
1 to 5 times the width W and 1/3 to 1/ of the external connection terminal thickness t.
There is a depth D of 2. The groove 25 is formed over the entire width of the external connection terminal 21, as shown in FIG. 1(b).

In the case of FIG. 2, the external connection terminal 22 has a solder pool groove 26 formed on the joint surface 22a near the periphery of the printed wiring board. This groove 26 also has a thickness t of the external connection terminal.
It has a width W of ~5 times and a depth D of 1/3 to 1/2 of the connection terminal thickness t, and an angle θ=3 on the outer side surface 26b.
It has an inclination of 0 to 60 degrees and is formed over the entire width of the external connection terminal 21.

In addition, in the case of the above-mentioned both grooves 25 and 26, the corner 2 on the front side of the groove bottom
5a and 26a are rounded. corner 25
The roundness of a and 26a is 115 to 1/ of the external connection terminal thickness t.
It is R (R) of 2.

In the case of FIG. 3, on the joint surface 23a of the external connection terminal 23,
As shown in FIG. 1.2, in addition to similar grooves 25 (26), three small grooves 27 for collecting solder are formed at the front. Each small portion 27 is 1/5 to 1/1/2 of the external connection terminal thickness t.
It has a width of about 2 mm and a roughly square or semicircular cross-sectional shape. The small part 26 is also formed over the entire width of the external connection terminal 23. Note that the number of small mantles 27 may be one.

The concave portion for the solder pool of the present invention is not limited to the above-mentioned groove, but may be a concave portion that is formed to be shorter than the entire width of the external connection terminal and not open to the side surface. The external connection terminal also does not need to have a constant thickness over its entire length;
The joint portion may be a thick terminal as shown in the figure.

In the case of these bonding and fixing, as shown in FIGS. 1 to 3, there is a sufficient solder pool space formed by the groove at the bonding location on the periphery of the printed wiring board, and a sufficient solder thickness is ensured here.

Next, how to use the semiconductor chip carrier of the present invention will be explained.

As shown in FIG. 5, after mounting the semiconductor chip 10 on the semiconductor chip mounting surface 1a and connecting the ends of the semiconductor chip 10 and the conductive pattern 3 with wires 11, the semiconductor chip 10 is sealed with resin to protect it. After forming the protective film 12, the semiconductor chip carrier A is placed on the motherboard B, and the other end side of the external connection terminal 2 (the external connection terminal is subjected to necessary processing such as cutting and bending at an appropriate stage). A conductive pattern (not shown) on the motherboard B is soldered and a secondary mounting process is performed. The resin sealing film 12 has two types: a ponting type in which the semiconductor chip portion and the wire connection portion are sealed, and a type in which the entire semiconductor chip carrier is sealed.

[For production]

In the case of the semiconductor chip carrier of the present invention, at the joint portion between the conductive pattern of the printed wiring board and the external connection terminal, a joint portion having a sufficient solder thickness and a uniform length can be stably secured. This is because there is a space for the solder to accumulate due to the recess in the joint surface of the external connection terminal.
This is because the Anda thickness is sufficiently thick here. Therefore, the bonding strength is sufficiently high and variations are reduced.

〔Example〕

Next, the present invention will be explained in detail. This invention is not limited to the following embodiments.

As a printed wiring board, the conductive pattern has a width of 0.2 to 0.
-5 cranes, length 1~1.51 wealth, pattern pitch 0.4~
A sample having a 0.65 m CuJi conductive pattern was prepared.

The external connection terminal is made of 42 alloy (Ni
42% Fe remaining) material and a Cu alloy material were prepared, and as for the shapes, those shown in Figs. 1 to 3 were prepared, respectively. The external connection terminal is slightly smaller than the conductive X turn,
The plate thickness is about 0.15 to 0.351. The groove for the solder pool was created by etching. Surface treatment with solder was also applied in advance.

High temperature solder with S n 3.5%, A g 1.5%, PB 95%, S n 5.0%, A g 2.5%, P
b A cream solder of 92.5% high temperature solder was applied to the conductive pattern by a silk screen method using a metal mask, and bonding and fixing was performed as described above.

When the bonding strength between the external connection terminal and the conductive pattern of the semiconductor chip carrier thus obtained was examined, it was found to be superior to that of the conventional method. When a strength test was conducted using the peeling method shown in FIG. 8, it was confirmed that peeling started at a tilt angle of 30 to 60 degrees, and that a bonding strength capable of withstanding the applied load at this time was secured.

A comparison after conducting a reliability test also confirmed that the bonding of the semiconductor chip carrier of the example was superior to that of the conventional one.

〔Effect of the invention〕

As described above, in the semiconductor chip carrier according to claim 1.2, the joint portion with sufficient solder thickness is uniform and stable at the joint portion between the conductive pattern of the printed wiring board and the external connection terminal. Therefore, the bonding strength is sufficiently high and there is little variation.

In the semiconductor chip carrier according to the second aspect of the present invention, since the bonded portion with sufficient solder thickness is located on the peripheral edge side of the printed wiring board, the bonding strength is higher and variation is reduced.

[Brief explanation of drawings]

FIG. 1(a) is a partial cross-sectional view showing an example of the main structure of a semiconductor chip carrier according to the present invention, and FIG. 2 and 3 are partial plan views, and FIG. 3 is a partial cross-sectional view showing another example of the structure of the main parts of the semiconductor chip carrier according to the present invention, and FIG. FIG. 5 is a perspective view showing the semiconductor chip carrier in use, and FIGS. 6 and 7 are partial sectional views showing the main structure of the conventional semiconductor chip carrier. FIG. 8 is a sectional view of the main part showing the state when measuring the bonding strength. A... Semiconductor chip carrier 1... Printed wiring board 2.21.22.23... External connection terminal 3.
...Conductive patterns 21a, 22a, 23a...Joint surfaces 25.26...Grooves for solder pool Agent Patent attorney Takehiko MatsumotoFigure 3Figure 4Figure 5Figure 5

Claims (1)

[Scope of Claims] 1. A semiconductor chip carrier comprising a printed wiring board on which a conductive pattern is formed around a chip mounting surface and an external connection terminal, the external connection terminal being soldered to the conductive pattern. A semiconductor chip carrier characterized in that a recess for a solder pool is formed on a bonding surface of an external connection terminal. 2. A recessed portion for collecting solder is a groove formed in the width direction at a position on the peripheral edge side of the printed wiring board on the bonding surface, and the groove is
2. The semiconductor chip carrier according to claim 1, wherein the semiconductor chip carrier has a width of 1 to 5 times the thickness t of the external connection terminal and a depth of 1/3 to 1/2 the thickness t of the external connection terminal.