JPH11220055A - BGA type semiconductor device and stiffener used in the device - Google Patents

Abstract

(57) Abstract: A BGA that reduces stress applied to solder balls at the time of board mounting and actual use, and does not peel off between the solder balls and the mounting board or between the solder balls and the BGA package body. To provide a semiconductor device. A BGA in which solder balls (6) are arranged in a lattice pattern on the lower surface of a package having a stiffener (1) disposed on a TAB tape (5), and a board is mounted using the solder balls (6).
In the die-shaped semiconductor device, at least a portion of the stiffener 1 on the side of the TAB tape 5 which is located immediately above the solder ball 6 is removed to form a dimple 2 or a through hole 3, thereby forming the solder ball 6 and the stiffener 1. Give elasticity between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a BGA (Ball Grid Array) type semiconductor device which is mounted on a substrate using solder balls, and to a stiffener used in the device.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size and improved in function, and in order to support these, the density of packages and the number of pins have been increased in accordance with the enhancement of functions of LSIs. In response, BGA-type semiconductor devices in which solder balls are arranged in a lattice pattern on the back surface of a package have been actively developed in order to use ball bumps as connection leads between a mounting substrate and a package.

[0003] The feature of this BGA type semiconductor device is that electrical connection with the substrate can be made over the entire surface of the package. The point is that it is possible to increase the number of pins without narrowing the inter-pitch. Also,
Taking advantage of this advantage, the size of the package can be reduced.

On the other hand, this BGA type semiconductor device is required to have a structure with good heat dissipation since the heat generation of the semiconductor chip is increasing with the increase in the degree of integration of the semiconductor chip. Also, the feature of the BGA type semiconductor device is that, by attaching solder balls to the entire surface of the package, it becomes possible to increase the number of pins while maintaining a relatively wide pitch by using these as electric external connection terminals. In the prior art,
To connect the electrodes of the semiconductor chip and the solder balls,
A multilayer wiring board based on glass epoxy resin or polyimide resin must be used. When a flexible wiring board made of a material having low rigidity such as a polyimide resin is used as the multilayer wiring board, flatness on the solder ball surface of the package becomes a problem in assembling and mounting the package. Therefore, a stiffener is usually attached to the top surface of the package body in order to ensure flatness on the solder ball surface of the package and to improve heat dissipation.

FIG. 3 shows the structure of a conventional BGA type semiconductor device provided with a stiffener. In the figure, (a) shows the BGA
FIG. 2 is a top view of the semiconductor device, and FIG.

A recess for mounting a semiconductor chip is formed at the center of the lower surface of the stiffener 1 made of a metal plate having a predetermined high thermal conductivity with a step, and the semiconductor chip 7 is placed at the center of the bottom of the recess via an Ag paste 10. Directly fixed. Around the concave portion, a TAB (Tape Automated Bonded), which is a flexible wiring board, is provided on the lower surface of the stiffener 1 with an adhesive 4 having an insulating property and a high thermal conductivity.
ng) The tape 5 is fixed.

A plurality of through holes (not shown) are provided in the TAB tape 5, wiring patterns such as copper foil are formed on both sides and in the through holes, and solder balls 6 are provided so as to cover the through holes. ing. The terminals on the semiconductor chip 7 and the circuit patterns (terminals) on the TAB tape 5 are bonded with Au wires 8, and the recess of the stiffener 1 including the semiconductor chip 7 is covered with a sealing resin 9.

In the semiconductor device configured as described above,
The heat generated by the semiconductor chip 7 is transmitted to the stiffener 1 and is radiated therefrom. Electrical connection with the mounting board is made by solder balls 6 provided on the TAB tape 5 as external connection bumps.

[0009]

By the way, as the stiffener, a metal plate having high thermal conductivity such as copper or stainless steel is usually used for the purpose of securing flatness (rigidity) of the package and heat radiation. Can be

However, these metal plates made of copper or stainless steel do not match the thermal expansion of the mounting board, and the solder ball portions have a resiliency (elasticity) as compared with the leads of a package using a lead frame such as a QFP. small. For this reason, at the time of board mounting and actual use, a considerable stress is applied to the solder ball due to a difference in thermal expansion between the stiffener and the mounting board, and between the solder ball and the mounting board or between the solder ball and the BGA package body. Is a problem because peeling may occur between the two.

Therefore, an object of the present invention is to solve the above-mentioned problems, to reduce the stress applied to the solder balls at the time of board mounting and actual use, and to reduce the stress between the solder balls and the mounting board or between the solder balls and the BGA package body. It is an object of the present invention to provide a structure of a BGA type semiconductor device which does not cause separation between the semiconductor devices and a stiffener used for the device.

[0012]

SUMMARY OF THE INVENTION The gist of the present invention is to remove a stiffener portion located immediately above a solder ball, whereby elasticity is provided between the solder ball and the BGA package body, and a BGA package is provided. The purpose is to alleviate the stress due to the difference in thermal expansion between the main body and the mounting board.

More specifically, in order to achieve the above object, in the BGA type semiconductor device according to the first aspect, a solder ball serving as an external connection terminal is formed on a lower surface of a package having a stiffener disposed on a wiring board in a lattice shape. In a BGA type semiconductor device in which the stiffener is mounted on a substrate using the solder balls, a space is formed by removing at least a stiffener portion of the surface of the stiffener immediately above the solder balls. Thus, elasticity is provided between the solder ball and the stiffener.

Further, the BGA type semiconductor device of claim 2 is
The space portion is formed of dimples having openings on the surface of the stiffener on the wiring board side and provided at the same pitch as the pitch of the solder balls.

According to a third aspect of the present invention, in the BGA type semiconductor device, the space portion is formed of a through hole penetrating from the surface of the stiffener on the wiring board side to the other surface, and the through hole is meshed at the same arrangement pitch as the solder balls. This is a configuration provided in a shape.

According to a fourth aspect of the present invention, in the BGA type semiconductor device, the stiffener has a concave portion for mounting a semiconductor chip on a surface on the wiring substrate side, and the space around the concave portion on the wiring substrate side around the concave portion. This is a configuration in which the units are arranged.

In the BGA type semiconductor device, the stiffener may be a stiffener having a hole for avoiding a semiconductor chip or a stiffener having no hole for avoiding a semiconductor chip. The latter includes an embodiment in which a concave portion for mounting a semiconductor chip is provided on the surface of the stiffener on the wiring substrate side, and the dimple or the through hole is provided on the surface on the wiring substrate side around the concave portion.

Next, the stiffener according to claim 5 is
A stiffener for a BGA type semiconductor device, wherein the stiffener is disposed on a wiring board and is mounted on the lower surface of the wiring board by solder balls arranged in a grid pattern on the lower surface of the wiring board.
A dimple having an opening on the solder ball side is provided on a surface of the stiffener on the wiring board side so as to face the solder ball on a one-to-one basis with the wiring board interposed therebetween.

Further, the stiffener according to claim 6 is:
In place of the dimple, a through-hole penetrating the stiffener is provided.

Further, the stiffener according to claim 7 is:
The surface on the wiring board side has a concave portion for mounting a semiconductor chip, and the dimple or the through hole is provided on the surface on the wiring substrate side around the concave portion.

The stiffener may be a stiffener having a hole for avoiding a semiconductor chip or a stiffener having no hole for avoiding a semiconductor chip. The latter includes an embodiment in which a concave portion for mounting a semiconductor chip is provided on the surface of the stiffener on the wiring substrate side, and the dimple or the through hole is provided on the surface on the wiring substrate side around the concave portion.

The BGA type semiconductor device of the present invention and the stiffener used in the device have a space portion such as a dimple or a through hole by removing a portion opposed to a joint portion of the solder ball, that is, a stiffener portion located immediately above the solder ball. Is formed, thereby providing elasticity between the solder ball and the stiffener, so that the solder ball is semi-fixed, so that the solder ball can be displaced to the space side to release the stress applied to the solder ball. it can. Therefore, the stress applied to the solder ball caused by the difference in thermal expansion between the stiffener and the mounting board during the mounting of the board and during actual use is reduced, and the problem between the solder ball and the mounting board or the Peeling between the ball and the BGA package body is prevented, and high reliability of mounting (joining) can be ensured.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 1 shows a top view and a cross section of a BGA type semiconductor device according to an embodiment of the present invention.

In FIG. 1, the semiconductor device has a stiffener 1 made of a material having a predetermined high thermal conductivity. The stiffener 1 is provided with a concave portion for mounting the semiconductor chip 7 on one surface thereof, that is, in the center of the lower surface. Further, the lower surface of the stiffener around the concave portion for mounting the semiconductor chip is joined with a solder ball 6. Dimples (hollows) 2 as spaces are formed at positions opposed to the parts, that is, at positions corresponding to the arrangement positions of the solder balls 6 as viewed in the direction in which the surface spreads. The dimples 2 are each formed in a semi-spherical cross section having an opening on the surface of the stiffener 1 on the wiring board side, and are provided at the same pitch as the pitch of the solder balls 6.

Copper is used as the material of the stiffener 1 in consideration of rigidity for ensuring the flatness of the package and good thermal conductivity. However, the stiffener 1 only needs to be made of a material having a predetermined high thermal conductivity. For example, the stiffener 1 can be made of a highly heat conductive metal such as aluminum. Besides metal, alumina, AlN,
The stiffener 1 may be formed using ceramics such as SiC and SiW.

The size of the dimple 2 was slightly larger than the diameter of the solder ball 6, and the depth was the same as the radius of the solder ball 6. This means that at least the stiffener portion of the surface of the stiffener 1 on the wiring board side which is located immediately above the solder ball 6 is removed to form a space, thereby providing elasticity between the solder ball 6 and the stiffener 1. This is for the purpose of providing a semi-fixed structure, and if the elasticity can be provided between the solder ball 6 and the stiffener 1, the size may be smaller than the diameter of the solder ball.

A TAB tape 5 as a flexible wiring board is adhered to the stiffener 1 configured as described above with an adhesive 4 having an insulating property and a high thermal conductivity. The dimple 2 is filled with a highly elastic resin 2a such as a silicone resin. The TAB tape 5 is provided with a plurality of through holes (not shown), wiring patterns such as copper foil are formed on both sides and in the through holes, and solder balls 6 are provided so as to cover the through holes.

A semiconductor chip 7 such as an IC chip is directly fixed to the center of the bottom surface of the recess formed at the center of the lower surface of the stiffener 1 with a step. The semiconductor chip 7 is bonded to the stiffener 1 with an Ag paste 10 or the like. The terminals on the semiconductor chip 7 and the wiring patterns (terminals) (not shown) on the TAB tape 5 are bonded by Au wires 8 to electrically connect the terminals. It is connected to the.

In the recess of the stiffener 1 including the semiconductor chip 7, the circuit surface side of the semiconductor chip 7 and the gap between the semiconductor chip 7 and the TAB tape 5 are:
It is covered and protected by the sealing resin 9.

The semiconductor device having the above structure is mounted on a mounting board (not shown) by using the solder ball surface as a mounting surface. At this time, since the stiffener 1 is provided, the stiffener has a desired rigidity and flatness on the solder ball surface side is ensured. For this reason, as in the prior art described with reference to FIG.
If the lower surface of the stiffener 1 remains flat, that is, if the stiffener portion corresponding to the bonding position of the semiconductor ball 6 remains flat and there is no space like the dimple 2, the heat between the stiffener 1 and the mounting substrate It is expected that a considerable stress will be applied to the solder ball 6 due to the difference in expansion.

However, in this embodiment, since the dimple 2 is provided on the lower surface of the stiffener 1 at a position facing the joint portion of the solder ball, the solder ball 6 is formed in the space of the dimple 2, more precisely, in the high elastic resin 2 a. Displaced to
The stress applied to the solder ball 6 can be released. In this sense, elasticity is provided between the solder ball 6 and the stiffener 1, and the solder ball 6 is semi-fixed. Therefore, according to this embodiment, the stress on the solder balls 6 generated due to the difference in thermal expansion between the stiffener and the mounting board during the mounting of the board and the actual use is reduced, and the soldering which has been a problem in the prior art is reduced. Prevention of peeling between the ball 6 and the mounting board or between the solder ball 6 and the BGA package body, and high mounting (joining)
Reliability can be ensured.

FIG. 2 shows a top view and a cross section of a semiconductor device according to another embodiment of the present invention.

In this embodiment, the dimple 2 in FIG. That is, instead of providing the dimples 2 on the lower surface of the stiffener 1, a through-hole 3 is provided at a position facing the joint portion of each solder ball 6 so as to penetrate the stiffener 1 vertically. The arrangement pitch of the through holes 3 is the same as the arrangement pitch of the solder balls 6.

Therefore, in the stiffener 1 of this embodiment, the through holes 3 facing the joint portion of the solder ball are formed around the concave portion for mounting the semiconductor chip on the lower surface of the stiffener 1 at the same arrangement pitch as the solder ball 6. It is arranged in a shape. Other configurations are the same as the embodiment of FIG.

In the case of this embodiment, the through-holes 3 have the same cross-sectional shape with a rectangular cross-section, and when viewed from the top view of FIG. 2A, the rectangles have a regular mesh shape (mesh shape). Are arranged. However, through hole 3
There is no restriction on the cross-sectional shape and arrangement of the solder balls.
It suffices if it is provided in accordance with the arrangement and size of. It is preferable that the size of these through holes 3 is slightly larger than the diameter of the solder ball 6.

In the embodiment of FIG. 2, as in the case of the embodiment of FIG. 1, there is no rigid portion in the stiffener 1 portion directly above the solder ball 6, so that the solder ball 6 can be displaced in response to stress. Is formed by the through-hole 3. For this reason, it is possible to reduce the stress on the solder balls generated due to the difference in thermal expansion between the stiffener 1 and the mounting board when the board is mounted and actually used.

In the above embodiment, the stiffener having no hole for avoiding the semiconductor chip has been described as an example.
The stiffener may be a stiffener having a hole for avoiding a semiconductor chip.

[0039]

As described above, according to the present invention, the following excellent effects can be obtained.

(1) B according to claim 1, 2, 3 or 4
According to the GA type semiconductor device, at least the stiffener portion of the stiffener on the wiring board side which is located immediately above the solder ball is removed, and a space such as a dimple or a through hole is formed there. The elasticity between the stiffener and the stiffener allows the solder ball to be semi-fixed, so the stress on the solder ball caused by the difference in thermal expansion between the stiffener and the mounting board during board mounting and actual use is reduced. However, peeling between the solder ball and the mounting board or between the solder ball and the BGA package body, which has been a problem in the prior art, can be prevented, and high mounting reliability can be ensured.

(2) According to the stiffener according to the fifth, sixth, and seventh aspects, the solder ball is provided on the surface on the wiring board side so as to face the solder ball on a one-to-one basis with the wiring board interposed therebetween. When a BGA type semiconductor device is mounted on a wiring board and mounted on a substrate, the difference in the thermal expansion between the stiffener and the mounting substrate causes the lower surface of the package to be provided. Even when stress is generated in the solder balls arranged in a lattice pattern, the stiffener portion directly above the solder ball does not have a rigid portion, so that the stress applied to the solder ball can be reduced. The rigidity of the lower surface of the package is maintained at a desired level by the stiffener itself, so that the rigidity of the package is not reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a BGA type semiconductor device according to an embodiment of the present invention, wherein FIG. 1 (a) is a top view and FIG. 1 (b) is a cross-sectional view.

2A and 2B are diagrams showing a structure of a BGA type semiconductor device according to another embodiment of the present invention, wherein FIG. 2A is a top view and FIG. 2B is a cross-sectional view.

3A and 3B are diagrams showing the structure of a BGA type semiconductor device according to the related art, wherein FIG. 3A is a top view and FIG. 3B is a cross-sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stiffener 2 Dimple (space part) 2a High elastic resin 3 Through-hole (space part) 4 Adhesive 5 TAB tape (wiring board) 6 Solder ball 7 Semiconductor chip 8 Au wire 9 Sealing resin 10 Ag paste

Claims (7)

[Claims] 1. A BGA type semiconductor device in which solder balls serving as external connection terminals are arranged in a grid pattern on the lower surface of a package having a stiffener disposed on a wiring board, and the board is mounted using the solder balls. With respect to the surface of the stiffener on the wiring board side, a space is formed by removing at least the stiffener portion located immediately above the solder ball,
A BGA type semiconductor device wherein elasticity is provided between the solder ball and the stiffener. 2. The stiffener according to claim 1, wherein the stiffener is formed of dimples having openings on the surface of the stiffener on the wiring board side and arranged at the same pitch as the pitch of the solder balls. BGA type semiconductor device. 3. The method according to claim 1, wherein the space portion is formed of a through hole penetrating from the surface on the wiring board side of the stiffener to the other surface, and the through holes are provided in a mesh at the same arrangement pitch as the solder balls. 2. The BGA type semiconductor device according to claim 1, wherein: 4. The stiffener has a recess for mounting a semiconductor chip on a surface thereof on the wiring board side, and the space is provided on a surface of the wiring board side around the recess. B according to claim 1, 2 or 3, wherein
GA type semiconductor device. 5. A stiffener for a BGA type semiconductor device, wherein the stiffener is disposed on a wiring board and is mounted on a lower surface of the wiring board by solder balls arranged in a lattice pattern on a lower surface of the wiring board. A dimple having an opening on the solder ball side so as to face the solder ball on a one-to-one basis with the wiring substrate interposed therebetween. 6. The stiffener according to claim 5, wherein a through-hole penetrating the stiffener is provided in place of the dimple. 7. The stiffener according to claim 5, wherein the stiffener has a recess for mounting a semiconductor chip on a surface on the wiring board side.