JP3264059B2 - Bonding tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding tool used for mounting a semiconductor device such as an IC or an LSI.

[0002]

2. Description of the Related Art In order to bring out the electrical characteristics of a semiconductor device, it is necessary to electrically connect an electrode formed on the semiconductor device to a lead of a package and the lead to an external terminal such as a wiring board. is there. Conventionally, the connection between the electrode on the semiconductor element side and the lead wire is made by using a thin metal wire made of gold or copper as a conducting wire and using a tool called a capillary.
A method called wire bonding in which the wires are bonded one by one, and a lead wire called a film carrier tape in which tin is plated on a patterned copper foil, and all electrodes on the semiconductor element are bonded using a bonding tool heated to a predetermined temperature. To connect all the leads to the TAB system (Tape A
This is performed by a method called “utomated bonding”.

On the other hand, a lead wire is connected to an external terminal such as a wiring board or a lead frame by a tin-plated lead wire, or a lead wire not formed and a solder electrode formed on the wiring board by screen printing or the like. Alternatively, a gold-plated lead wire is bonded to a gold-plated or silver-plated lead frame by using a bonding tool heated to a predetermined temperature.

[0004] The bonding tools used here include Mo, Fe-Ni alloy, Ni alloy, Ti and Ti.
Alloys, W and W alloys, Fe-Ni-Co alloys and other metal tool shank parts are used to improve the flatness, wear resistance, temperature distribution, etc. of gas phase synthetic diamond and diamond Crystal, sintered diamond, cBN
A tool to which a tool tip made of a hard material such as a sintered body or silicon nitride is adhered is used, and is heated to a predetermined temperature by inserting a heater into a tool shank of a bonding tool. .

[0005]

In recent years, semiconductor devices have been increasing in size and length due to multifunctionality and high integration.
Furthermore, in order to improve the mounting efficiency, a method of mounting a plurality of semiconductor elements collectively has begun to be adopted, and correspondingly, a bonding tool has been required to be larger and longer. In particular, when joining the lead wire of a film carrier tape to a wiring board or lead frame, the pressing load of the bonding tool at the time of mounting tends to increase not only to increase the size of the tool tip but also to obtain reliable bonding strength It is in.

However, as the bonding surface becomes larger or longer, the tip end of the tool also becomes larger, and therefore, the area of connection with the tool shank tends to increase. Generally, the hard substance used at the tool tip has a lower coefficient of thermal expansion than the tool shank. Therefore, these two
When the two parts are joined by brazing, the thermal stress generated at the joint interface is further increased, which has caused a problem that the tool tip is separated from the tool shank during use. Further, even when peeling did not occur, the tool pressing surface was warped due to the influence of internal thermal stress, and the tip of the tool was cracked due to repeated mounting loads.

In order to solve this problem, a method of fixing the joint between the tool shank portion and the tool tip portion with a screw or a clamp pin has been proposed by the present applicant (Japanese Patent Laid-Open No. 3-191538). However, in this case, even the joint surface processed with sufficient care has a warp of several μm to 10 μm, and further, due to the influence of the surface roughness, the entire joint surface of the tool tip and the tool shank portion. Does not contact uniformly, the heat applied by the heater to the tool shank side is not sufficiently transmitted to the tool tip, and the temperature distribution of the tip pressing surface and the ability to follow the rise and fall of temperature, ie, the temperature response, It was inferior to the accessory.

In addition, since the tool tip mainly made of a brittle material is fixed directly to the tool shank by screwing, clamping pin fastening, etc., a tightening force is applied to a narrow area of the tool tip, so that the tool is not used. In addition, there was a problem that the tip of the tool was chipped, cracked, and loosened.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a bonding tool for semiconductor mounting comprising a tool tip and a tool shank is provided. Gold between the tool shank parts,
It has one or more intermediate layers selected from soft metals such as silver, copper, platinum, tantalum, nickel and aluminum, and the tool tip has an area of 10 mm ² or more provided on a metal stopper. The tool has a flat surface, and is mechanically fixed by being pressed against the tool shank side by the stopper, and the thickness of the soft metal of the intermediate layer is one layer. It is 0.005 mm or more and 10 mm or less.

According to the bonding tool of the present invention, a soft metal is inserted into the joining interface between the tool tip and the tool shank, whereby the joining interface is sufficiently adhered to each other by utilizing the deformation of the metal, so that the joining tool from the shank side can be used. Heat can be easily transmitted to the tool tip, and the temperature distribution and temperature responsiveness at the tip can be improved. The soft metal layer preferably has a thickness of 0.005 mm or more and 10 mm or less.

Further, since the tool tip is applied with a tightening force to the tool shank side on a flat surface of 10 mm ² or more provided on the stopper, and the tool tip does not directly contact the screw, it is hard material. The tip of the tool does not crack or chip, so that it can be used stably for a long time. Also, gold,
By inserting one or more metals selected from soft metals such as silver, copper, platinum, tantalum, nickel, and aluminum, the mounting force applied to the tool tip becomes more uniform.

[0012]

The bonding tool according to the present invention will be described below in detail with reference to FIGS.

The bonding tool according to the present invention has a structure as shown in an exploded perspective view of FIG.
Is the tool shank, 3 is gold, silver, copper, platinum, tantalum,
An intermediate layer made of a soft metal such as nickel and aluminum;
Reference numeral 4 denotes a metal stopper, and reference numeral 5 denotes a fixing screw.

For joining the tool tip 1, the intermediate layer 3, and the tool shank 2, a fastener 4 on the tool tip 1 is screwed to the tool shank 2 with a screw 5 without using brazing. The mechanical joining is performed by tightening. The tool tip 1 is pressed downward by the stopper 4 from above to be fixed to the tool shank 2 via the intermediate layer 3. In this case, the screw 5 is the tool tip 1
The screw 5 and the tool tip 1 and the intermediate layer 3 do not come into direct contact with each other because the screw 5 passes through the projections at both ends of the stopper 4 which coincide with the cutout portions of the intermediate layer 3.

FIGS. 2 and 3 show a bonding tool integrated by screwing. The bonding tool is mounted on a bonding device (not shown) at a device mounting portion 8 of the tool shank 2. At the time of use, a cartridge heater is attached to the heater hole 6 of the bonding tool, and a thermocouple is attached to the thermocouple hole 7, and then the bonding tool is heated to a predetermined temperature so that the semiconductor lead wire and the lead frame are connected. The pressure bonding with the wiring board or the like is performed using the front end pressing surface 9.

FIG. 4 is a plan view of the bonding tool according to the present invention as viewed from above. The contact surface 10 between the stopper 4 and the tool tip 1 is a plane of 10 mm ² or more. FIG. 5 is a partially cutaway sectional view taken along line AA of FIG.
As shown in (1), the joining portion between the tool tip 1 and the tool shank 2 is not in direct contact with the intermediate layer 3. Also, the screw 5 and the tool tip 1 are not in direct contact,
The tool tip 1 is pressed in a surface contact state with the stopper 4 at the contact surface 10, and is fastened and fixed to the tool shank 2 together with the intermediate layer 3.

In the present invention, since the tool tip 1 is attached to the tool shank 2 by mechanical joining via the soft metal intermediate layer 3, the intermediate layer 3 is deformed, and the tool tip 1 and the tool are attached. A uniform contact is made over the entire joint surface of the shank portion 2. For this reason, compared to the conventional mechanical joining, in which there is no soft intermediate layer and there is a gap in the joint due to the warped surface roughness of the joining surface, the joint is more evenly applied from the entire joint to the tool tip when the tool shank is heated. Heat is transmitted. This provides a uniform temperature distribution during heating,
A bonding tool having excellent descent response can be obtained.

Further, as a mechanical joining means, a tool tip 1
Is fastened to the tool shank portion 2 via the stopper 4 with the area of 10 mm ² or more provided on the stopper 4 without providing a screw hole or the like. No stress is applied, and the tip of the tool is less likely to crack or chip during use as in the case of mechanical joining using a conventional screw or the like directly at the tip of the tool.

[0019]

EXAMPLE A tool tip made of silicon carbide and a tool shank made of a tungsten alloy having two tip pressing surfaces each having a length of 30 mm and a width of 1 mm, and a tool shank made of a tungsten alloy as an intermediate layer, having a thickness of 0.1 mm and a purity of 99.9% gold. Was screwed with a stopper via. The screw is heated to a working temperature of 550 ° C. and tightened at that temperature from the viewpoint of preventing loosening during use, and then, as shown in FIG.
The screw tip 11 was machined to have the same curvature as the inner diameter of the heater hole 6, and the bonding tool of the present invention having a structure in which the screw was not loosened during use by inserting the heater was prepared.

On the other hand, for comparison, a bonding tool was prepared without an intermediate layer of gold, and a tool having a tool shank and a tool tip joined by silver brazing was prepared at 550 ° C.
From the temperature distribution, flatness, and normal temperature of the tip pressing surface at 55
A comparison was made on the durability of the joint when heating and cooling to 0 ° C. were repeated. Table 1 shows the results.

[0021]

[Table 1]

[0022]

As described above, according to the bonding tool of the present invention, the soft metal inserted into the joining interface between the tool tip and the tool shank allows the joining interface to be sufficiently formed by utilizing the deformation of the metal. The tool is brought into close contact, heat from the shank side is easily transmitted to the tool tip, and the temperature distribution and temperature responsiveness at the tip can be improved. Furthermore, since the joining of the tool tip is performed by fastening to the tool shank with a plane of 10 mm ² or more provided on the stopper, it does not directly contact the joining member such as a screw and is made of a hard substance. The tool tip does not crack or chip,
Stable use over a long period of time becomes possible.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the structure of a bonding tool according to the present invention.

FIG. 2 is a perspective view of the bonding tool of the present invention.

FIG. 3 is a front view of the bonding tool of the present invention.

FIG. 4 is a plan view of the bonding tool of the present invention.

FIG. 5 is a partially cutaway sectional view taken along line AA shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tool tip part 2 Tool shank part 3 Intermediate layer 4 Stopper 10 Contact surface between the stopper and the tool tip part

Claims (2)

(57) [Claims] 1. A bonding tool for semiconductor mounting comprising a tool tip and a tool shank, wherein a gold, silver, copper, platinum, tantalum, nickel, aluminum or the like is provided between the tool tip and the tool shank. It has one or two or more intermediate layers selected from soft metals, and the tool tip is pressed against the tool shank side by a plane having an area of 10 mm ² or more provided on a metal stopper. A bonding tool, which is mechanically fixed at 2. The bonding tool according to claim 1, wherein the thickness of the soft metal of the intermediate layer is 0.005 mm or more and 10 mm or less per layer.