JP3286448B2 - Thermocompression bonding tool, semiconductor device and method of manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The thermocompression bonding method is a bonding method in which plated members to be bonded are pressurized and heated using a bonding tool, and is used for connection between a lead of a semiconductor chip and a lead frame or for a semiconductor device. Widely used for substrate mounting. The present invention relates to a head structure and a material of a bonding tool for thermocompression bonding.

[0002]

2. Description of the Related Art In a thermocompression bonding method, there are a solid phase joining in which two kinds of metals are joined in a solid phase state and a liquid phase joining in which a liquid phase is joined.

[0003] In the solid-phase bonding, a member plated with a metal having a high melting point such as Au-Au or Au-Ag is heated at a temperature lower than the melting point (300 to 500 ° C) while pressing with a bonding tool. It is a method of joining. When the members are pressurized, the surface oxide film and the contaminant film are destroyed, and the members are joined while exposing a pure metal surface.

In liquid phase bonding, a member of a plating combination that forms a liquid phase having a relatively low melting point, such as Au-Sn, is pressed while being heated. The surface oxide film and the contaminant film are removed by the liquid phase formed at the joint interface, and the members are joined by forming a reaction layer.

In the liquid phase bonding, wettability and reactivity between the pressurized surface of the head provided in the tool and the melt of the member to be bonded pose a problem. When a head made of a metal material is used, since the head has high wettability and reactivity with the melt, the melt adheres to the pressing surface of the head. for that reason,
At the end of joining, the members to be joined are pulled through the melt,
Has a negative effect. Further, since the melt adheres to the pressing surface, there is a problem that the temperature distribution and the pressing force on the pressing surface become non-uniform. Therefore, the pressing surface must be periodically cleaned (polished).

As a method of preventing contamination of the head pressing surface due to adhesion of the melt, there is a method of using a nonmetal material having poor wettability with the melt for the head portion. Generally, diamond having a very high thermal conductivity is used as the material of the head portion, and among them, relatively inexpensive sintered diamond is often used. In this case, the pressurized surface is less likely to be contaminated than a metal head. However, the sintered diamond contains a large amount of a sintering aid mainly composed of a metal material such as molybdenum (Mo) and cobalt (Co). For this reason, as the number of times of bonding increases, the sintering aid is chipped off, a melt enters the portion, and the pressing surface deteriorates. In order to solve this problem, recently, JP-A-2-224349 and JP-A-3-191538 using a single crystal diamond produced by a vapor phase synthesis method as a head material without using a sintering aid have been recently used. A method described in the gazette has been devised. Further, a bonding tool described in Japanese Patent Application Laid-Open No. 4-114440 has been devised in which a ceramic is used as a head material, or a thin film of a nonmetallic material is formed on a pressing surface of a head made of a metal material.

However, a non-metallic material (diamond, BN, etc.) having low reactivity with the melt and poor wettability is used as a head material for preventing the above-described bonding failure due to the adhesion of the melt. The pressurized surface warps due to the difference in physical properties including the thermal expansion coefficient of the shank and the head material, and the flatness deteriorates. Generally, the coefficient of thermal expansion of a nonmetallic material is smaller than that of a metal material. In such a case, the pressing surface warps in a concave shape. If the pressing surface warps, the parallelism between the head and the member to be joined will be deviated. The deviation of the parallelism is
The synergistic effect with the variation in the thickness of the members to be joined causes the one-sided contact of the tool. Since the pressing force cannot be transmitted evenly at one end of the tool, the reliability of the joining degree decreases.

[0008]

As means for obtaining the degree of parallelism between the head and the member to be joined, Japanese Patent Application Laid-Open No. 4-27345 has been proposed.
No. 4 discloses a bonding tool.

[0009] In the bonding tool, the shank holds the tool material so as to be able to move up and down, and suppresses one-sided contact. However, since there is a space between the tool material and the shank, it is conceivable that the pressing force of the shank and the heat of the heater are not well transmitted to the tool material.

Further, there is a bonding head holding mechanism described in Japanese Patent Application Laid-Open No. Hei 4-243144 in which an elastic body is provided between the holding mechanism main body and the mounting shaft for transmitting the pressing force of the shank and the heat of the heater. However, since this elastic body covers the entire mounting shaft, in view of the problem that is considered to require a considerable capacity, the object of the present invention is to prevent the melt from adhering to the head, An object of the present invention is to provide a bonding tool for thermocompression bonding that minimizes contact of a pressing surface.

[0011]

In the bonding tool for thermocompression bonding of the present invention, a non-metallic material such as ceramics having poor wettability with metals such as tin (Sn) and solder is used as a head material .

For a tool whose head can be detached from the shank, an elastic intermediate material having high thermal conductivity is provided between the shank and the head.

[0013]

By using the non-metallic material for the head,
The melt hardly adheres. Therefore, the number of times of cleaning the pressing surface can be reduced, and the life of the tool is extended.

Further, with respect to a bonding tool made of a metal material, a pressurized surface having poor wettability with a melt is formed by an oxide film on the surface.

[0015] In addition, the above-mentioned intermediate member can minimize the contact of the tool, which becomes a problem during joining, to a minimum.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermocompression bonding tool according to an embodiment of the present invention will be described below.

In FIG. 1, the thermocompression bonding tool has a shank 1 as a tool body, a T-shaped cross-section including a horizontal portion and a vertical portion, and a pressing surface 14 which is a member to be joined 15 (see FIG. 2), and an intermediate member 3 inserted between the shank 1 and the head 2.

At the center of the shank 1 is provided a heater insertion opening 5 for inserting a heater for applying heat to the bonding tool. In addition, on the bottom of the shank 1, the head 2 and the intermediate member 3 are held.
The head holding parts 4 formed to face each other are provided. The holding portion 4 sandwiches the vertical portion below the horizontal portion of the T-shaped head 2 with a slight gap therebetween, and
The intermediate member 3 is detachably inserted into the holding portion 4.

By using a material having high heat conduction and soft properties for the intermediate member 3, heat conduction from the shank 1 to the head 2 is improved, and the parallelism between the head 2 and the member 15 to be joined is improved. The deviation of the degree can be corrected by the deformation of the intermediate member 3.

The material of the shank 1 is a nickel-base heat-resistant alloy such as Inconel or Monel, or a material having a low thermal expansion coefficient such as Invar or Kovar alloy (at 450 ° C.).
Metal materials, tungsten (W), molybdenum (M
o) Low thermal expansion metals such as can be used.

Examples of the material used for the head 2 include oxide ceramics such as alumina (Al ₂ O ₃ ) and partially stabilized zirconia (PSZ), aluminum nitride (AlN),
Silicon nitride (Si ₃ N ₄ ), boron nitride (BN), silicon carbide (Si
Non-oxide ceramics such as C) are conceivable, but Al ₂ O ₃ , AlN, and BN, which have good thermal conductivity, are suitable.

The metal material used for the intermediate member 3 is as follows.
A soft metal material such as aluminum (Al) or copper (Cu) is suitable. However, since Al has a low melting point of 660 ° C., Cu is used when performing a bonding operation at a high temperature. Note that, instead of these metal materials, a heat-resistant polymer that elastically deforms, for example, a polyimide may be used.

As shown in FIG. 2, when the bonding member 15 is bonded by the bonding tool, a load pressure is applied to the intermediate member 3 via the head 2. When the parallelism between the member to be joined 15 and the head 2 is shifted, the intermediate member 3 includes the shank 1 and the head 2.
Deform between. If the applied pressure is smaller than the yield strength of the intermediate member 3, the deviation of the parallelism between the member 15 to be joined and the head 2 is corrected by the elastic deformation of the intermediate member 3. Then, the pressing force of the head 2 can be evenly applied to the member 15 to be joined. When the load pressure exceeds the yield strength of the intermediate member 3, the displacement is corrected by plastic deformation of the intermediate member 3. Then, the pressing force of the head 2 can be evenly applied to the member 15 to be joined.

Also, as shown in FIG.
Since the parallelism between the table 21 on which the substrate 16 having the substrate 16 is placed and the head 2 is shifted, the parallelism between the member 15 to be joined and the head 2 may be shifted. In such a case, before starting the bonding operation, a normal bonding operation may be performed after applying a load pressure enough to cause the intermediate member 3 to undergo plastic deformation and correcting a certain degree of parallelism deviation in advance. .

Here, Cu, Ni, or polyimide is
A description will be given of a case where the intermediate member 3 having a shape of 20 mm in length, 2 mm in width, and 3 mm in thickness is used.

The physical properties of Cu, Ni, and polyimide are shown in Table 1.
As shown in FIG. Table 1 is a table showing physical property values of an example of a material used for the intermediate material.

[0027]

[Table 1]

When Cu is used for the intermediate material 3, the applied load 24
Up to 0 kg, the parallelism deviation can be corrected by elastic deformation. At this time, the possible correction amount for the deviation is
It is about 1.5 μm. Since the applied load is usually in the range of 100 to 150 kg, Cu undergoes elastic deformation. Further, since the yield strength of Cu sharply drops when the temperature exceeds 400 ° C., when the tool is used at a tool temperature of 400 ° C. or higher, plastic deformation may occur even with the load of 100 to 150 kg described above.

Ni can be used as the intermediate material 3.
However, the heat resistance is higher than that of Cu, but the Young's modulus is high, so that the effect of adjusting the parallelism is small.

When polyimide is used for the intermediate member 3, when the applied load is 50 kg, the compressive strain of the polyimide is:
0.2 mm. Therefore, compared to the case where a metal material is used as the intermediate material, the amount of correction of the parallelism shift becomes larger. However, since polyimide has lower heat resistance than Cu and Ni, the tool temperature needs to be 300 ° C. or less.

Considering the physical properties such as the thermal expansion coefficient and the elastic modulus of the material used for the head 2 and the intermediate member 3 as described above, the joining conditions such as the temperature and the pressure, the workability and the parallelism adjustment, the holding part 4 It is better to design the T-shaped space portion slightly larger so that the head 2 and the intermediate member 3 can move to some extent.

Further, even if the member 15 to be joined is displaced in a direction perpendicular to the direction shown in FIG. 2, the intermediate member 11 and the head 12 are rounded as shown in FIG. To give it a roundness. The holding portion 4 holds the T-shaped head 12 with a slight gap 10 formed between the vertical portion below the horizontal portion of the T-shaped head 12. Therefore, the member to be joined 15 is
Is perpendicular to the deviation shown in FIG.
However, by swinging in the direction of the arrow B shown in FIG.

FIGS. 4 and 5 show a bonding tool for thermocompression bonding according to this embodiment using a rectangular parallelepiped head.

The bonding tool includes a shank 1 as a tool body, a rectangular head 6, and an intermediate member 3 inserted between the shank 1 and the head 6.

The shank 1 serves as a head holding means, a head accommodating portion 23 provided at the lower end of the shank 1, a support shaft 7 for supporting the rectangular parallelepiped head 6, and an axial movement of the support shaft 7. Regulating means for regulating. The regulating means includes, for example, a plate-shaped regulating member 17,
A regulating member holding portion 1 for detachably holding the regulating member 17
8 is provided. The head 6 has an insertion hole 9 into which the support shaft 7 is inserted. The diameter of the insertion hole 9 is adjusted by the support shaft 7 so as to correct the parallelism deviation described later.
It is slightly larger than the diameter. The head accommodating portion 23 is provided with a groove 13 that opens downward, and a bearing hole 22 that receives the support shaft 7 on a side surface of the groove 13.
The regulating member holding portion 18 is provided with an insertion hole 8 into which the support shaft 7 is inserted.

When the head 6 and the intermediate member 3 are accommodated in the groove 13, the support shaft 7 is inserted into the insertion hole 8
Then, it is inserted into the insertion hole 9 through the bearing hole 22. The head 6 and the intermediate member 3 are held by the bearing holes 22 supporting both ends of the support shaft 7. Since the head 6 moves up and down with respect to the support shaft 7 at the time of bonding, the intermediate member 3 can correct the deviation of the parallelism with the member to be joined. Therefore, the diameter of the insertion hole 9 is determined in consideration of the displacement.
It is determined. After the support shaft 7 is inserted, the regulating member 17 is inserted into the regulating member holding portion 18, so that the supporting shaft 7 does not fall off.

Next, a description will be given of a tool in which the head and the shank are integrated with each other and are composed of only a metal material.

FIG. 6 is a cross-sectional view of a bonding tool in which a tool made of only a metal material is subjected to high-temperature oxidation treatment to form an oxide film on the tool surface.

As the shank material, an iron (Fe) -chromium (Cr) alloy, for example, a ferritic stainless steel (Fe-25)
~ 30wt% Cr) can be used. Iron (Fe) -chromium (Cr) alloy has excellent workability,
Cr oxide can be easily formed.

The processing method of the tool is described below.

First, the Fe—Cr alloy is processed into a tool shape. Then, the tool is subjected to a high-temperature oxidation treatment at about 1000 ° C. for a certain time to form a Cr oxide film of about 0.1 mm. In the present invention, the Cr oxide film is formed not only on the tip of the tool but also on the entire surface of the tool as shown in FIG. The Cr oxide film is inferior in heat conduction as compared with a metal material. Therefore, if the Cr oxide film is formed on the entire tool as described above, the escape of heat from the heater can be reduced.

After the high-temperature oxidation treatment, the pressurized surface is finished and polished to obtain flatness. In this case, the flatness of the pressurized surface is higher when polishing is performed in a high temperature state. Since this Cr oxide film has poor wettability with Sn and solder, the adhesion of the melt hardly occurs. Since the high-temperature strength of Fe-Cr alloy is not so high, when high pressure is required as in solid-phase bonding, 4
It is necessary to perform bonding at 50 ° C. or lower.

[0043]

According to the bonding tool of the present invention,
It becomes difficult for the molten metal to adhere to the pressing surface.

Further, since an intermediate material is provided for a bonding tool whose head can be replaced, a bonding defect due to a one-sided contact of the tool, which is a problem at the time of bonding, is reduced.
Furthermore, since the head, the intermediate member, and the shank are not joined to each other, warpage due to a difference in the coefficient of thermal expansion of each member hardly occurs.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bonding tool for thermocompression bonding according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the bonding tool for thermocompression bonding shown in FIG.

FIG. 3 is a front view of a bonding tool for thermocompression bonding when the head and the intermediate member shown in FIG. 1 are subjected to a rounding process.

FIG. 4 is a perspective view of a thermocompression bonding tool of the present invention when a rectangular parallelepiped head is used.

FIG. 5 is a partial sectional view of the bonding tool for thermocompression bonding shown in FIG. 4;

FIG. 6 is a cross-sectional view of the thermocompression bonding tool of the present invention in which an oxide film is formed on the surface of the tool.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shank, 2 ... T-shaped head, 3 ... Intermediate material, 4 ... Head holding part, 5 ... Heater insertion port, 6 ... Rectangular head
Reference numeral 7: support shaft, 8: insertion hole of the head housing portion, 9: insertion hole of the head, 10: gap, 11: intermediate material processed by R, 12
... R-shaped T-shaped head, 13 ... Groove, 14 ... Pressing surface, 15 ... Member to be joined, 16 ... Substrate, 17 ... Regulatory member,
18: regulating member holding portion, 19: oxide film, 20: R processed portion, 21: table, 22: bearing hole, 23: head housing portion

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichiro Miyano 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Production Research Laboratory (72) Inventor Akio Hasebe 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Production Technology Laboratory (72) Koji Serizawa, Inventor 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Production Technology Laboratory (56) References JP-A-59-161832 (JP, A (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/60

Claims (9)

(57) [Claims] 1. A thermocompression bonding tool comprising: a shank made of a metal material; and a T-shaped head made of ceramics and having a horizontal portion and a vertical portion, wherein a bonding portion between the shank and the T-shaped head is provided. The shank has a head holding portion at a lower end thereof, and the head holding portion sandwiches a vertical portion below a horizontal portion of the T-shaped head with a gap therebetween, and A bonding tool for thermocompression bonding, wherein a material and the T-shaped head are detachably held. 2. A thermocompression bonding tool comprising: a shank made of a metal material; and a head made of ceramics, wherein an intermediate member is provided between the shank and the head, The head holding means comprises: a support shaft for supporting the head; and a shaft holding means for holding the support shaft. The head is provided with an insertion portion for inserting the support shaft, A part of a shaft is inserted into the insertion portion, and the shaft holding means holds the head via the support shaft. 3. The shaft holding means according to claim 2, wherein the shaft holding means is provided at a lower end of the shank.
A head accommodating portion accommodating at least a part of the head, wherein the head accommodating portion includes a groove that opens downward, and a locking portion that locks the support shaft on a side surface of the groove. Characteristic bonding tool for thermocompression bonding. 4. The thermocompression bonding tool according to claim 3, wherein said shaft holding means further comprises a regulating means for regulating an axial movement of said support shaft. 5. The locking member according to claim 4, wherein the locking portion is a bearing hole into which a part of the support shaft is inserted, wherein the restricting means includes: a restricting member for closing the bearing hole; A thermocompression bonding tool, comprising a holding member detachably held and a regulating member holding portion provided in the head accommodating portion. 6. The thermocompression bonding tool according to claim 1, wherein the intermediate member is a soft metal material or a polymer having elasticity. 7. A shank made of a metal material and a ceramic.
Bonding head with a head composed of
A shaping tool, wherein the shank is connected to the head via an elastic intermediate material.
Thermocompression bonding characterized by having holding means for holding the
For bonding tools. 8. The method according to claim 1, 2, 3, 4, 5, 6, or 7.
Use the bonding tool for thermocompression bonding
Make sure that the lead and lead frame are connected
Characteristic semiconductor device. 9. The method according to claim 1, 2, 3, 4, 5, 6, or 7.
Use the bonding tool for thermocompression bonding
It is characterized by connecting the lead of the
Semiconductor device manufacturing method.