JP2001144214A - Semiconductor device and bonding structure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device having excellent heat shock resistance and a bonding structure thereof having a prolonged lifetime of bonding by preventing thermal stress due to difference in the coefficient of thermal expansion from concentrating at the parts where the semiconductor device and a circuit board are bonded through solder balls. SOLUTION: A semiconductor element 2 is die bonded to one side of a circuit board 1 having electrode parts formed on the opposite sides thereof and then it is wire bonded and sealed with resin 3. Subsequently, solder balls 5, 6 are mounted at the electrode parts 4 on the opposite side of the circuit board 1 thus constituting a (BGA type or CSP type) semiconductor device 7. A solder ball 6 being mounted on at least one peripheral electrode part 4 among a plurality of electrode parts 4 on the circuit board 1 is made of a material having tensile strength higher than that of the material of other solder balls 5. The solder balls 5, 6 of the semiconductor device 7 are positioned at the electrode parts 9, 10 on a circuit board 8 and soldered thus jointing the semiconductor device 7 and the circuit board 8 electromechanically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a bonding structure between the semiconductor device and a circuit board.

[0002]

2. Description of the Related Art Conventionally, a package which is a semiconductor device formed by electrically bonding a semiconductor element to a circuit board includes a QFP (Quad Flat Package), a TCP, and the like.
(TapeCarrier Package), BGA (Ball Grid Arra)
y), CSP (Chip Scaleor Size Package), CC
B (Controlled Collapsed Bonding) and the like are known.

[0003] Regarding the BGA type semiconductor device (package), for example, US Pat. No. 5,239,198, US Pat. No. 5,285,352, US Pat.
No. 307 and U.S. Pat. No. 5,397,921, each of which describes a BGA type semiconductor device in which a semiconductor element (semiconductor chip) is bonded on a circuit board (interposer) and then sealed with a resin. And a structure in which solder balls are mounted and melted on wiring electrode portions on a surface of the circuit board opposite to the semiconductor element mounting surface, and the BGA type semiconductor device is mounted on a second circuit board (mounting board). In this case, the semiconductor device is soldered to the wiring electrode portion of the second circuit board (mounting board) via the solder ball of the BGA type semiconductor device.

The configuration of such a conventional BGA type semiconductor device will be described with reference to FIGS. 2A and 2B. A circuit board 101 having a circuit pattern and electrode portions on both front and back surfaces will be described.
The semiconductor element 102 is die-bonded and wire-bonded to one surface of the semiconductor device 102. Thereafter, the semiconductor element 102 is sealed by transfer molding with a resin 103, and then a solder paste is printed on the electrode portion 104 on the surface opposite to the surface on which the semiconductor element 102 is mounted, and solder balls are formed on the solder paste. 105 is mounted. Thereafter, through a reflow process, the solder paste and the solder balls 105 are melted, and the solder balls 105 are attached and formed to form external terminals. Then, the flux of the solder paste is removed by washing to form a (BGA type) semiconductor device 107.

Next, as shown in FIG. 2B, a solder paste is applied on the electrode portion 109 of a second circuit board (mounting board) 108 having a circuit pattern and electrode portions on both sides, and a BGA type The electrode portion 104 of the semiconductor device 107 and the electrode portion 109 of the second circuit board 108 are positioned, and a solder ball 105 as an external terminal is mounted on the solder paste. Thereafter, the solder balls 105 and the solder paste are melted through a reflow process, and soldering is performed. Thereby, the electrode portion 104 of the semiconductor device 107 and the circuit board 1
08 electrode portion 109 is electromechanically bonded.

A CSP type semiconductor device (package)
See, for example, US Pat. No. 5,346,861
No. 5,592,025, the CSP type semiconductor device is opposite to the semiconductor element mounting surface of a flexible substrate in which semiconductor elements (semiconductor chips) are bonded and resin-sealed. A cream solder is printed on the electrode portion on the side surface, a solder ball is placed thereon, and the solder ball is integrally formed with the electrode portion of the flexible substrate by a reflow soldering process. When mounting the CSP type semiconductor package on the second circuit board (mounting board), the solder balls of the CSP type semiconductor device are applied to the wiring electrode portions of the second circuit board (mounting board) coated with cream solder. The electrodes of the flexible substrate of the CSP type semiconductor device and the electrodes of the second circuit board are electrically and mechanically joined through the reflow soldering process after positioning and mounting.

Further, as for a CCB type semiconductor device (package), see, for example, US Pat. No. 3,292,24.
No. 0, U.S. Pat. No. 3,303,393, and in U.S. Pat. No. 3,303,393, a circuit pattern for electrically connecting electric circuit elements is formed. A ball-shaped terminal element is mounted on the chip element substrate via solder coating in order to electromechanically bond the circuit board thus formed and the chip element substrate on which the semiconductor element is mounted, and the terminal portion of the circuit pattern of the circuit board is formed. There is disclosed a configuration in which the terminal and the terminal element are aligned with each other, and are flowed through a solder reflow process to be soldered.

[0008]

However, a bonding structure of a semiconductor device formed by bonding a BGA or a CSP, which is a conventional semiconductor device, to a second circuit board (mounting board) is as follows. Problems.

Referring to FIG. 2, the semiconductor device (B
The GA type semiconductor package 107 is made of a composite material, and particularly made of a plurality of materials having different coefficients of thermal expansion. That is, the coefficient of thermal expansion of the silicon of the semiconductor element 102 is 2 to 3 ppm / ° C., that of the BT range and the circuit board 101 made of glass is about 13 to 17 ppm / ° C., and the resin 103 is as close as possible to silicon. The coefficient of thermal expansion is set. In addition, FR-
4, the coefficient of thermal expansion of the circuit board 108 is 13 to 17 pp.
m / ° C.

[0010] Therefore, when a thermal shock test is performed on a bonding structure formed by bonding the semiconductor device (BGA type semiconductor package) 107 to the second circuit board 108, a thermal bond based on the difference in thermal expansion coefficient is found in the solder bonding portion. Stress occurs,
It will be subjected to thermal stress.

[0011] Thermal stress is applied more to the peripheral portion of the solder joint than to the center thereof. That is, when the difference in thermal expansion coefficient is Δα, the difference in temperature is ΔT, and the distance from the neutral point or the constraint point is L, the elongation Δl is represented by the following equation. Δl = L × Δα × ΔT

The shape of the solder ball 105 is generally barrel-shaped, so that the barrel-shaped upper connection portion (the circuit board 1) is formed.
The thermal stress stress concentrates on the electrode portion 104 (side of the first electrode substrate 104) and the lower connection portion (the side of the electrode portion 1109 of the second circuit board 108), and cracks occur. In the worst case, breakage occurs. That is, the bonding life is shortened, which may cause a trouble in the market.

As a measure to avoid this, the semiconductor device 1
07 and the resin as an underfill material are injected into the solder ball gaps of the second circuit board 108, and the solder balls 10
Although there is a method of dispersing the thermal stress applied to 5, the repair becomes difficult or the cost increases.

Although the BGA type has been described above as an example, the CSP type has similar problems.

In view of the foregoing, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and has been made in view of the above, and has been made in consideration of the difference in thermal expansion coefficient at the joint between a semiconductor device and a circuit board via solder balls. It is an object of the present invention to provide a semiconductor device which can avoid thermal stress concentration caused by the above, has excellent thermal shock resistance, and can extend a bonding life, and a bonding structure thereof.

[0016]

In order to achieve the above object, a semiconductor device according to the present invention comprises a circuit board having a large number of electrodes on both front and back sides, and an electronic circuit element is joined to an electrode on one side of a circuit board. In a semiconductor device which forms a circuit and has a large number of metal balls as external terminals on the other surface, at least one metal ball is made of a material having higher tensile strength than other metal balls.

In the semiconductor device of the present invention, a metal ball made of a material having a higher tensile strength than other metal balls is disposed at an end of the circuit board or is arranged around an outer periphery of the circuit board. Is preferred.

Further, the bonding structure of the semiconductor device of the present invention is as follows.
A circuit board having a large number of electrode parts on both front and back sides is bonded to an electrode part on one side of a circuit board. In a bonding structure of a semiconductor device in which solder bonding is performed corresponding to each of the portions, at least one of a number of metal balls in the semiconductor device is made of a material having a tensile strength greater than other metal balls, and the at least one metal ball is formed. A ball is soldered to an electrode portion of the electrode portion of the second circuit board corresponding to the position of the at least one metal ball.

In the semiconductor device bonding structure of the present invention,
It is preferable that the metal balls made of a material having a higher tensile strength than other metal balls are arranged at the end of the circuit board or are arranged around the outer periphery of the circuit board.

[0020]

According to the present invention, the material of at least one of the metal (solder) balls, which is the external terminal of a semiconductor device (semiconductor package) such as a BGA type or a CSP type, is made smaller than the material of the other metal balls. By using a material with high tensile strength, it is possible to avoid the thermal stress caused by the difference in thermal expansion coefficient being concentrated on the metal ball joint, and to eliminate defects due to serious soldering due to cracks and breaks in the joint. Can be excellent in thermal shock resistance,
A joining structure that improves the joining life can be obtained.

Further, a metal ball made of a material having a higher tensile strength than that of the other metal balls is BGA type, C type
By arranging the semiconductor device at the end or the periphery of a semiconductor device such as an SP type device, the above-described effects are further enhanced.

[0022]

Embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1A is a sectional view of a semiconductor device according to a first embodiment of the present invention, and FIG. 1B is a sectional view of the semiconductor device mounted on a second circuit board. It is sectional drawing which shows the joined structure joined.

In FIG. 1A, a semiconductor element (semiconductor chip) 2 is die-bonded and wire-bonded to one surface of a circuit board (interposer) 1 having a circuit pattern and electrode portions formed on both front and rear surfaces. After that, the semiconductor element 2 is sealed by transfer molding with a resin 3, and then a solder paste is printed on the electrode portion 4 on the surface opposite to the surface on which the semiconductor element 2 is mounted, and external terminals are formed on the solder paste. Solder balls 5 and 6 are mounted. Here, the solder balls 6 are mounted corresponding to the four electrode portions 4 (only two are shown in FIG. 1) located in the peripheral portion among the plurality of electrode portions 4 of the circuit board 1. The solder balls 5 are mounted corresponding to the other electrode portions 4. The solder balls 5 are made of Sn-37% Pb which is generally used. However, the four solder balls 6 in the peripheral portion described above are smaller than the material of other solder balls 5 (Sn-37% Pb). It is made of a material having high tensile strength and elongation (for example, Sn-3.5% Ag-0.5% Cu).

Thereafter, in a reflow process, the solder paste and the solder balls 5, 6 are melted, and the solder balls 5, 6 are respectively attached to the electrode portions 4 to form external terminals. Thereafter, the semiconductor device (semiconductor package) 7 is formed by washing and removing the flux of the solder paste.

The semiconductor device (semiconductor package) 7 configured as described above is mounted on a second circuit board (mounting board) 8 having circuit patterns and electrode portions on both surfaces, as shown in FIG. Joined. Here, in the electrode portions 9 and 10 of the second circuit board 8 on the side where the semiconductor device 7 is joined, the Sn portion is formed by a usual method on the electrode portion 9 corresponding to the mounting portion of the solder ball 5 of the semiconductor device 7. A solder paste of -37% Pb is applied, and then the peripheral electrode portion 10 (only two are shown in FIG. 1) corresponding to the portion on which the four solder balls 6 are mounted in the peripheral portion of the semiconductor device 7. A solder paste of Sn-3.5% Ag-0.5% Cu is applied with a dispenser.

Next, the solder balls 5, 6 as external terminals of the electrode portion 4 of the semiconductor device 7 and the electrode portions 9, 10 of the second circuit board 8 are positioned, respectively, and the solder balls 5, 6 of the semiconductor device 7 are positioned. The solder paste is mounted on the solder paste of the second circuit board 8 and then soldered by reflow heating to melt the solder balls 5 and 6 and the solder paste, thereby forming the electrode portion 4 of the semiconductor device 7 and the second circuit. Electrodes 9 and 10 of substrate 8 are electromechanically joined via solder balls 5 and 6.

As described above, as a material of the solder ball and the solder paste corresponding to the electrode portion located in the peripheral portion among the plurality of electrode portions, a material having a high tensile strength (Sn-3.
5% Ag-0.5% Cu) and a normal material (Sn) as a material for other solder balls and solder paste inside.
(-37% Pb), and a reliability test (a temperature change of -25 ° C. to 125 ° C. of 10 ° C.) was performed using a bonding structure in which the semiconductor device and the second circuit board were bonded via these solder balls.
(00 cycles), the electrical characteristics were measured, and good results were obtained.

That is, by forming the solder ball (6) and the solder paste in the peripheral portion using a material having a higher tensile strength than the material of the other solder balls (5) and the solder paste inside, a joint structure is formed. It is possible to prevent thermal stress caused by a difference in expansion coefficient from being concentrated on the solder ball joint, and to improve the crack resistance and improve the joint life without underfill.

In the above-described embodiment, a material having high tensile strength is used for the four solder balls on the outer peripheral portion. However, the material is not limited to four, and any one of the ends may be used. A material having high tensile strength may be used for all the outer and peripheral solder balls, and in this case, crack resistance and joining life can be further improved.

(Second Embodiment) In this embodiment, both the solder balls and the solder paste on the outer peripheral portion are made of Sn-2.0.
% Ag-0.75% Cu-3% Bi, and the other solder balls and solder paste inside are made of normal Sn-
It was made of 37% Pb, and the other configuration was the same as that of the embodiment shown in FIG.

Also in this embodiment, the reliability test (−25)
After 1000 cycles of a temperature change of from 125 ° C. to 125 ° C.), good results were obtained, and crack resistance and joining life could be improved.

As described above, the solder balls usually have Sn
Although -37% Pb is used, materials having higher tensile strength and elongation than the material of Sn-37% Pb include Sn-Ag, Sn-Ag-Cu, and Sn-Ag-
There are Cu-Bi-based, Sn-Zn-based, Sn-Zn-Bi-based and other materials, and any material of these materials has a higher tensile strength than ordinary Sn-37% Pb. If there is, it can be used as a material of the solder ball in the present invention.

[0034]

As described above, according to the present invention,
By making at least one metal ball of a plurality of metal balls, which are external terminals of a semiconductor device such as a BGA type or a CSP type, a material having a higher tensile strength than a material of other metal balls, a difference in thermal expansion coefficient is obtained. The thermal stress caused by the metal ball joint can be prevented from being concentrated on the joint, the joint can be prevented from serious defects due to soldering due to cracks or breakage, and it has excellent thermal shock resistance and longer joint life. An improved bonding structure can be obtained.

Further, a metal ball made of a material having a higher tensile strength than that of the other metal balls is a BGA type,
By arranging it around the semiconductor device such as SP type,
The effect becomes more pronounced.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a semiconductor device according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view illustrating a bonding structure in which the semiconductor device is bonded to a second circuit board. is there.

2A is a cross-sectional view of a conventional general semiconductor device, and FIG. 2B is a cross-sectional view illustrating a bonding structure in which the conventional general semiconductor device is bonded to a second circuit board. It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Semiconductor element 3 (sealing) resin 4 Electrode part 5 Solder ball 6 Solder ball 7 Semiconductor device (semiconductor package) 8 Second circuit board (mounting board) 9, 10 Electrode part

Claims (6)

[Claims] An electronic circuit is formed by bonding an electronic circuit element to an electrode portion on one surface of a circuit board having a large number of electrode portions on both front and back surfaces, and has a plurality of metal balls as external terminals on the other surface. In a semiconductor device, at least one metal ball is made of a material having higher tensile strength than other metal balls. 2. The semiconductor device according to claim 1, wherein a metal ball made of a material having higher tensile strength than other metal balls is disposed at an end of the circuit board. 3. The semiconductor device according to claim 1, wherein metal balls made of a material having a higher tensile strength than other metal balls are arranged around the outer periphery of the circuit board. 4. A metal ball which is a large number of external terminals of a semiconductor device forming an electronic circuit by joining an electronic circuit element to an electrode portion on one surface of a circuit board having a large number of electrode portions on both front and back surfaces. In a bonding structure of a semiconductor device, which is solder-bonded corresponding to each of the electrode portions of the circuit board, at least one of a large number of metal balls in the semiconductor device is made of a material having a higher tensile strength than other metal balls, A bonding structure for a semiconductor device, wherein the at least one metal ball is solder-bonded to an electrode portion of the electrode portion of the second circuit board corresponding to the position of the at least one metal ball. 5. The bonding structure for a semiconductor device according to claim 4, wherein a metal ball made of a material having higher tensile strength than other metal balls is disposed at an end of the circuit board. 6. The bonding structure for a semiconductor device according to claim 4, wherein metal balls made of a material having higher tensile strength than other metal balls are arranged on the outer periphery of said circuit board.