JPH0851129A - Pulse heating tool and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the drop-off of the tip end of a tool in a long time soldering operation for by covering the part of the tool side surface including a brazing material surface exposed except a machine mounting part with metal or ceramic having low reactivity with melted solder. CONSTITUTION:Cemented carbide alloy covered with polycrystalline diamond is used at the end of a tool. A shank is formed of Mo and W or their alloy. The end of the tool is connected to the shank by a brazing material. The brazing material has a melting point of 650-1200 deg.C and contains Au, Ag' and Cu or their alloy as main ingredients. The surface of the exposed brazing material and the end of the tool near it are covered on the surface except the side of the shank and the mechanical mount of the tool with a covering material in a range of thickness of 1-100mum. As the covering material, at least one type of metal selected from Cr, Mo, W, Ni having a low reactivity with the melted solder or ceramic is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding tool which is a thermocompression bonding tool used for mounting semiconductor elements such as ICs and LSIs on a substrate, and in particular, a pulse used for solder bonding. It concerns heat type tools.

[0002]

2. Description of the Related Art In recent years, various electronic devices using semiconductor elements have been developed, and the technological progress in this field is remarkable. In order to bring out the electrical characteristics of a semiconductor element and to fully exert its performance, the electrodes formed on the element and the leads of the package are joined (inner lead bonding), and the leads and external terminals such as a printed wiring board. It is necessary to join with (outer lead bonding). Conventionally, the electrodes of the semiconductor element and the leads of the package have been joined by a method of joining metal thin wires (bonding wires) made of gold, copper or the like one by one with a tool called a capillary, that is, wire bonding. Recently, instead of this wire bonding, a mounting method using a wireless bonding technique that does not use a bonding wire has been attracting attention due to its excellent features such as high mounting efficiency and flexibility in package design. Of these, the film carrier (C
TAB (Tape Automated Bondin), in which a wiring pattern is formed on a laminated tape of u foil and resin and Sn or Au plating is applied)
The g) method has been put to practical use for mounting LCD driver etc. Further, the TAB method mounting is used not only in such inner lead bonding but also in the outer lead bonding process. In outer lead bonding by the TAB method, outer leads of a film carrier are joined to a printed wiring board or a lead frame which is an external terminal. In the case of joining with a printed wiring board, Cu plated with Sn or the like
Of the lead and the substrate electrode of Au or the like are joined by soldering. Further, in the case of joining with the lead frame, Au on the film carrier tape and Ag on the lead frame are joined by thermocompression bonding. A tool called a bonding tool is used for thermocompression bonding in mounting of these TAB methods, but recently, a tool with dramatically improved performance has been developed by using diamond as a tool tip material. In particular, a tool in which a specific base material is coated with polycrystalline diamond by a vapor phase synthesis method is used as a tool tip material (Japanese Patent Laid-Open No. 2-224349, Japanese Patent Application No. 6-6290).
No. 5) has been widely used due to its excellent heat resistance and wear resistance of the tool.

[0003]

As described above, the tools disclosed in Japanese Patent Application Laid-Open No. 2-224349 and Japanese Patent Application No. 6-62905 are most widely used at present due to various excellent features. In particular, there is a problem to be further improved in the application of bander bonding in the outer lead bonding process. That is, the tool of Japanese Patent Application No. 6-62905 has the structure shown in FIG. 1, but when this tool is used for soldering for a long time, the polycrystalline diamond itself at the tip of the tool is large. Despite the fact that no damage is seen, the tool tip end comes off the brazed portion and the tool life is reached. The cause of such problems is that the solder melted and evaporated during welding adheres to the brazed part of the tool and diffuses into the brazing material, resulting in a change in the brazing material composition and the formation of brittle intermetallic compounds. The strength of the brazed joint is reduced. In order to solve the above problems, the present invention is directed to Japanese Patent Application No. 6-6290.
By further improving the invention of No. 5 specification, it is intended to provide a pulse heating tool in which the tip of the tool does not fall off even if it is used for a long time in the application of soldering.

[0004]

The present invention is a pulse heat tool and a method for manufacturing the same as shown in the following (1) and (2). (1) A metal or ceramic in which a tool tip and a shank are joined by a brazing material, and a portion of a side surface of the tool including the exposed surface of the brazing material is low in reactivity with molten solder except for a machine mounting portion. A pulse heat tool characterized by being coated with. (2) After brazing the tool tip and the shank, covering the side surface of the tool including the exposed surface of the brazing material with a metal or a ceramic having low reactivity with molten solder, except for the machine mounting portion. A method for manufacturing a characteristic pulse heat tool. Further, the present invention includes the following aspects (3) to (18). (3) The pulse heat tool according to (1) above, wherein the metal to be coated is at least one selected from Cr, MO, W, Ni, Pd, and Pt. (4) The ceramic to be coated is Al ₂ O ₃ , SiO ₂ ,
The pulse heat tool according to (1) above, which is at least one selected from ZrO ₂ and TiO ₂ . (5) The pulse heat tool according to the above (1), (3) or (4), which has a coating thickness of 1 to 100 μm. (6) The above-mentioned (1), wherein the tip of the tool is a cemented carbide coated with polycrystalline diamond.
The pulse heat tool according to (3), (4) or (5). (7) The shank is at least one selected from Mo and W, (1), (3),
The pulse heat tool according to (4), (5) or (6). (8) The brazing material contains any one of Cu, Ag and Au as a main component and has a melting point of 650 to 1,200 ° C. (1), (3), (4), ( 5),
The pulse heat tool according to (6) or (7). (9) The method for producing a pulse heat tool according to the above (2), wherein the metal to be coated is at least one selected from Cr, Mo, W, Ni, Pd and Pt. (10) The coating ceramic is Al ₂ O ₃ , Si
(2) or (9) above, which is at least one selected from O ₂ , ZrO ₂ and TiO _2.
Manufacturing method of pulse heat tool. (11) The method for manufacturing a pulse heat tool as described in (2), (9) or (10), wherein the coating thickness is 1 to 100 μm. (12) The above-mentioned (2), wherein the tip of the tool is a cemented carbide coated with polycrystalline diamond.
The method for manufacturing a pulse heat tool according to (9), (10) or (11). (13) The shank is at least one selected from Mo and W, (2),
The method for manufacturing a pulse heat tool according to (9), (10), (11) or (12). (14) The brazing material contains Cu, Ag, or Au as a main component and has a melting point of 650 to 1,200 ° C. (2), (9), (10), ( 11),
(12) or the manufacturing method of the pulse heat tool of (13). (15) The method of coating a metal is any one of a plating method, a PVD method and a CVD method (2), (9), (1)
The method for manufacturing a pulse heat tool according to 1), (12), (13) or (14). (16) PVD method, C
The above (2), (10), (11), (12), (1) which is either the VD method or the hydrolysis method of a metal alkoxide.
3) or the manufacturing method of the pulse heat tool of (14). (17) The pulse heat tool according to (8), wherein the brazing material contains Ti, Sn, In, or Ni in addition to the main component. (18) The pulse heat tool according to (14) above, wherein the brazing material contains Ti, Sn, In, or Ni in addition to the main component.

[0005]

The pulse heat tool of the present invention is an improvement of the one having a structure in which the tool tip and the shank are joined by a brazing material. That is, except for the machine mounting portion of the tool having such a structure, the portion of the side surface of the tool including the exposed surface of the brazing material is covered with a metal or ceramic having low reactivity with molten solder. On the tool tip,
In particular, as disclosed in Japanese Patent Application No. 6-62905,
It is preferable to use a cemented carbide coated with polycrystalline diamond. This is because this member has excellent characteristics required for the pulse heat tool, such as thermal response, temperature distribution, and durability. In addition, the shank is preferably selected from Mo and W or their alloys from the viewpoint of suppressing the generation of thermal stress due to the difference in thermal expansion between the shank and the constituent member of the tool tip as much as possible. The tip of the tool and the shank can be joined by any known method, but the method of using a brazing material having a melting point of 650 to 1,200 ° C. is particularly effective. Here, as the brazing material, Au, Ag and Cu
Alternatively, an alloy containing any of these alloys as a main component and other elements (for example, Ti, Sn, In, Ni, etc.) to the extent that the characteristics of the brazing material are not impaired is used. Such a brazing material has a shear strength of 20 to 30.
A high joint strength of kg / mm ² can be realized.
In the present invention, after brazing the tool tip and the shank, the part of the side surface of the tool including the exposed surface of the brazing material is coated with a metal or ceramic having a low reactivity with the molten solder, except for the machine mounting portion. is necessary. Specifically, as shown in FIG. 2, coating is performed so as to cover the exposed brazing material surface and the tool tip side surface and the shank side surface in the vicinity thereof. The area to be coated may extend beyond the range shown in FIG. 2 without impairing the tool performance, but the polycrystalline diamond coating surface of the tool tip and the machine attachment portion of the shank should not be coated. This is because coating the tool tip surface only impairs the properties of the polycrystalline diamond and does not have any good effect on preventing the tool tip from falling off. Also, with respect to the machine mounting portion of the shank, when the coating material is a ceramic having no conductivity, power cannot be supplied from the machine, and therefore coating is only a new problem. As a material for coating, specifically, C
At least one metal selected from r, Mo, W, Ni, Pd, and Pt, or an alloy thereof, or Al
_At least one ceramic selected from ₂ O ₃ , SiO ₂ , ZrO ₂ and TiO ₂ or their composite oxides is used. Since these materials have low reactivity to molten solder or have a small diffusion coefficient, it is possible to prevent the composition change of the brazing material. As a coating method, any known method can be applied. For example, when the material to be coated is a metal, PVD (Physical Vaper Depositio) such as plating, sputtering or ion plating is used.
n), CVD (Chemical Vapor Deposition), etc. can be used. In the case of ceramics, PVD, CVD,
It is more effective to hydrolyze and coat the metal alkoxide. In addition, in order to remarkably exhibit the coating effect, it is necessary to set the coating thickness to 1 to 100 μm.
This is because if it is thinner than 1 μm, the effect as the blocking layer may be reduced. Further, when the coating is thicker than 100 μm, the adhesion strength with the coated brazing material is reduced, and peeling easily occurs during use, which is not preferable. The pulse heat tool manufactured by such a process is used for solder joining compared to a tool without coating treatment,
It is possible to maintain high brazing strength for a long time. Hereinafter, the present invention will be specifically described with reference to examples.

[0006]

【Example】

(Example 1) 88% by weight of WC, 7% by weight of TiC, C
20 mm x 2 mm x 2 cemented carbide containing 5% by weight of o
It was processed into a shape of mm. After that, this cemented carbide is
A heat treatment of holding the temperature at 1,420 ° C. for 1 hour in a N ₂ atmosphere of Torr and then cooling to room temperature in a vacuum atmosphere was performed. By this heat treatment, microscopic protrusions made of a solid solution carbide of W and Ti are generated on the surface, and the gap between these protrusions is filled with Co eluted from the inside of the cemented carbide. Became clear. This cemented carbide is immersed in nitric acid kept at 25 ° C to dissolve and remove only Co that is eluted, so that the surface is covered with microscopic projections of (W, Ti) C having a length of 5 µm. A cemented carbide was produced. Next, using this cemented carbide as a base material, it was placed inside a hot filament CVD apparatus so that a surface of 20 mm × 2 mm to be a tool tip became a coated surface, and polycrystalline diamond was coated for 30 hours. Table 1 shows the synthesis conditions.

[0007]

[Table 1]

The surface of the recovered cemented carbide has a thickness of 40 μm.
It was revealed that m of polycrystalline diamond was coated. This polycrystalline diamond coated cemented carbide is Mo
Made of shank, melting point 800 ℃, weight composition 68Ag
Bonding was performed using a -27Cu-5Ti brazing material. As a result of the evaluation of the shear strength, the joint strength of this brazing material was 22.
It was confirmed to be Kg / mm ² . Then, the polycrystalline diamond at the tip of the tool was processed into a mirror-finished state of 0.08 μm in terms of Rmax by a diamond grindstone.
The thickness of polycrystalline diamond after mirror finishing is 20 μm.
Met. Regarding the tool obtained by the above method,
Further, a treatment for coating the surface of the brazing material with the method shown in Table 2 and the metal material was performed. The coating was performed around the exposed side surface of the brazing material shown in FIG. In addition, as a comparison, a tool without this coating treatment was also prepared.

[0009]

[Table 2]

In order to evaluate the durability of these tools in soldering applications, a tool having a tip temperature of 400 ° C. was repeatedly pressed 800,000 times onto a plate made of solder having a thickness of 5 mm. The results are shown in Table 3. The shear strength in the table is the value after the above repeated evaluation of the tool in which the tip of the tool did not come off.

[0011]

[Table 3]

From this table, the tool No. of the present invention subjected to the coating treatment is shown. Even if the A to D are used for a long time of 800,000 times, the same high bonding strength as that before the use is maintained, while the conventional tool No. which is not subjected to the coating treatment. In E, it became clear that the tip of the tool dropped off after a relatively short number of times of use. It was found that the cause was that the molten solder and the brazing material were alloyed and changed into an alloy composition with low strength by analysis of the brazed surface of the tool tip that fell off. In addition, the above No. In F, although the tip of the tool did not fall off, the bonding strength was significantly reduced. It is presumed that the thickness of the coated Mo was 0.2 μm, which was too thin to be effective. In addition, No. Regarding G, the tip of the tool fell off after a relatively short time of use, because the coated Ni was too thick (300 μm), so partial peeling occurred during use and the brazing material of molten solder was formed from that part. It is considered that this is due to the alloying of.

(Example 2) A cemented carbide containing 90% by weight of WC, 5% by weight of TaC and 5% by weight of Co was 30 mm.
It was processed into a shape of × 2 mm × 1 mm. Then, this cemented carbide was held at a temperature of 1,380 ° C. for 2 hours in a CO atmosphere of 150 Torr, and then heat-treated for cooling to room temperature in a vacuum atmosphere. By this heat treatment, microscopic projections made of solid solution carbides of W and Ta are generated on the surface, and the gaps between these projections are filled with Co eluted from the inside of the cemented carbide. Became clear. This cemented carbide is dipped in hydrofluoric acid maintained at 50 ° C to dissolve and remove only the eluted Co, thereby covering the surface with microscopic projections of (W, Ta) C having a length of 7 μm. A broken cemented carbide could be produced. Next, using this cemented carbide as a base material, it was placed inside the microwave plasma CVD apparatus so that the surface of 30 mm × 2 mm to be the tool tip became the coating surface, and the polycrystalline diamond was coated for 25 hours. Table 4 shows the synthesis conditions.

[0014]

[Table 4] It was revealed that the surface of the recovered cemented carbide was coated with polycrystalline diamond having a thickness of 50 μm. This polycrystalline diamond-coated cemented carbide was applied to a W shank with a melting point of 860 ° C and a weight composition of 60Au-37Cu-.
Bonding was performed using a brazing material of 3In. In addition, according to the evaluation of the shear strength, the bonding strength of this brazing material is 25 kg / mm ²
It was confirmed that After that, the polycrystalline diamond at the tip of the tool was processed into a mirror-finished surface of 0.07 μm in Rmax display with a diamond grindstone. The thickness of the polycrystalline diamond after mirror finishing was 25 μm. Further, the side surface of the tool near the brazing layer was coated with a ceramic thin film utilizing hydrolysis of metal alkoxide according to the following steps. That is, the tool shown in FIG. 2 except for the covering portion of the tool is covered with a masking tape, immersed in a solution prepared by diluting silicon ethoxide with isopropyl alcohol, and then pulled up. It was heated for 1 hour, dried and cured. By this treatment, the SiO ₂ thin film having a thickness of 5 μm could be coated only on the coating portion shown in FIG. Tool No. obtained in this way With respect to H, the corrosion resistance to molten solder was evaluated in the same manner as in Example 1. For comparison, the tool N without this coating process
o. I was also evaluated. As a result, the conventional tool no. In No. 1, which is the tool of the present invention, the tip of the tool dropped off when the evaluation was repeated 20,000 times. For H, no change was seen in the brazed joint strength even after repeated evaluation of 800,000 times. No. In I, Au, which is a component of the brazing material, and Sn, which is a component of the solder, react with each other to form a brittle intermetallic compound (AuS
n, AuSn ₂ , AuSn ₄ ), but No. H
It was confirmed that the covered SiO ₂ thin film prevented this.

Example 3 85% by weight of WC, (Ti,
A cemented carbide containing 7% by weight of Ta and C and 8% by weight of Co was processed into a shape of 40 mm × 1 mm × 1 mm. After that, the cemented carbide is treated in an N ₂ atmosphere of 80 Torr for 1,
After the temperature was kept at 350 ° C. for 2 hours, a heat treatment of cooling to room temperature in a vacuum atmosphere was performed. By this heat treatment, microscopic projections made of solid solution carbides of W, Ti and Ta are formed on the surface, and the gaps between these projections are filled with Co eluted from the inside of the cemented carbide. It became clear. This cemented carbide is dipped in hydrofluoric nitric acid kept at 80 ° C to dissolve and remove only Co that has been dissolved out to obtain (W, Ti, Ta) having a length of 6 µm.
A cemented carbide whose surface was covered with microscopic projections of C could be produced. Next, using this cemented carbide as a base material, it was placed inside a hot filament CVD apparatus so that the surface of 40 mm × 1 mm to be the tool tip became the coated surface, and the polycrystalline diamond was coated for 50 hours. Table 5 shows the synthesis conditions.

[0016]

[Table 5]

The surface of the recovered cemented carbide has a thickness of 80 μm.
It was revealed that m of polycrystalline diamond was coated. This polycrystalline diamond coated cemented carbide is Mo
Made of shank, melting point 900 ℃, weight composition 60Cu
Bonding was performed using a brazing material of -30Au-10Ni. still,
According to the evaluation of shear strength, the joint strength of this brazing material is 2
It was confirmed to be 6 Kg / mm ² . After that, the polycrystalline diamond at the tip of the tool was processed into a mirror-finished surface of 0.07 μm in Rmax display with a diamond grindstone. The thickness of the polycrystalline diamond after mirror-finishing is 40
μm. This tool was further coated by various methods shown in Table 6 to complete a pulse heat tool. The coating method is the same as in Example 1 or 2. For comparison, a tool without coating was also prepared.

[0018]

[Table 6] In order to evaluate the performance of these tools, pulse heating was performed in a cycle of 15 seconds so that the tool tip temperature was 400 ° C., and outer lead bonding of the printed wiring board was performed. The results are shown in Table 7, and the conventional tool No. in which the surface of the brazing material is not coated. In U, the tip of the tool fell off after bonding 30,000 times,
All the tools of the present invention endured 800,000 times of bonding, and no change was observed in the bonding strength.

[0019]

[Table 7]

[0020]

By adopting the structure of the present invention, a bonding tool which is superior in corrosion resistance to molten solder in comparison with conventional tools can be realized. That is,
The reliability of the bonding strength at the tip of the tool, which was a problem with the conventional pulse heat tool having a brazed structure, is significantly improved, and the good characteristics inherent to the diamond tool can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a typical structure of a pulse heating tool using polycrystalline diamond as a tool tip surface.

FIG. 2 is a perspective view showing an example in which the pulse heat tool shown in FIG. 1 is subjected to a coating treatment according to the present invention.

Claims (14)

[Claims] 1. A metal in which a tool tip and a shank are joined by a brazing material, and a portion of a side surface of the tool including the exposed surface of the brazing material is low in reactivity with molten solder except for a machine mounting portion. Or a pulse heat tool characterized by being coated with ceramic. 2. The coating metal is Cr, Mo, W, N
The pulse heat tool according to claim 1, wherein there is at least one selected from i, Pd, and Pt. 3. The coating ceramic is Al ₂ O ₃ , S
The pulse heat tool according to claim 1, wherein the pulse heat tool is at least one selected from iO ₂ , ZrO ₂ and TiO ₂ . 4. The pulse heat tool according to claim 1, wherein the coating thickness is 1 to 100 μm. 5. The tool tip portion is made of a cemented carbide coated with polycrystalline diamond.
The pulse heat tool according to any one of 4 above. 6. The shank is at least one selected from Mo and W. 1.
The pulse heat tool according to any one of 1. 7. The pulse according to claim 1, wherein the brazing material contains Cu, Ag or Au as a main component and has a melting point of 650 to 1,200 ° C. Heat tool. 8. After brazing the tool tip and the shank, a part of the side surface of the tool including the exposed surface of the brazing material is covered with a metal or a ceramic having a low reactivity with the molten solder except for the machine mounting portion. A method for manufacturing a pulse heat tool, which is characterized by the above. 9. The coating metal is Cr, Mo, W, N.
9. The method for manufacturing a pulse heat tool according to claim 8, wherein the method is at least one selected from i, Pd and Pt. 10. The ceramic to be coated is Al ₂ O ₃ ,
9. The method for manufacturing a pulse heat tool according to claim 8, wherein the pulse heat tool is at least one selected from SiO ₂ , ZrO ₂ and TiO ₂ . 11. The method for manufacturing a pulse heat tool according to claim 8, wherein the coating thickness is 1 to 100 μm. 12. The tool tip portion is made of a cemented carbide coated with polycrystalline diamond.
11. The method for manufacturing a pulse heat tool according to any one of 1 to 11. 13. The shank is at least one selected from Mo and W.
13. The method for manufacturing a pulse heat tool according to any one of 12. 14. The pulse according to claim 8, wherein the brazing material contains Cu, Ag, or Au as a main component and has a melting point of 650 to 1,200 ° C. Method of manufacturing heat tool.