JP2002160016A - Tool for bending lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die and a punch, of which working surfaces coming into contact with a lead frame are coated with diamond, enabling easy polishing of the diamond coated surfaces, thereby causing no defect due to the polishing upon the production of the die and the punch for bending a lead frame. SOLUTION: The working surfaces of a die and a punch, which make contact with the lead frame, and bonded with a diamond chip synthesized in a vapor phase by means of soldering, adhesives etc. The parts to be bonded to the diamond chip are bonded to a base material separated from the bodies of the die and the punch. Thereby polishing of the diamond chip is more simplified and the bodies and the diamond chip are reusable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bending die and a punch used for forming an outer lead frame of an IC / LSI package.

[0002]

2. Description of the Related Art IC / L used as electronic components incorporated in various electronic devices such as computers and control devices.
The outer lead of the SI package is bent and formed into a predetermined shape.

A die and a punch as shown in FIGS. 7 and 9 are used as the molding tool. SKD steel or cemented carbide is generally used as a material for the tool, and the die and the punch have an integral structure. The portion where the outer lead mainly slides is lapped.

As a molding method, there is a method as shown in FIGS. The method shown in FIG. 11 uses a tool for bending a gull wing-shaped lead, and the lead set on the die as shown in FIG. And the lower surface side of the lead hits the die as the punch descends, and is formed into a shape similar to the die.

As another molding method, a DIP shown in FIG.
There is also a method of bending a type of package, in which a lead is sandwiched between a pressure pad and a die, and a punch descends to bend the lead. When the punch is lifted after bending, the lead springs back and springs up. Therefore, the lead is formed in consideration of the springback amount.

The leads of an IC / LSI package are generally plated with solder in order to make it easier to mount the solder on the substrate and to improve the corrosion resistance of the leads. As shown in FIG. 11, when the punch is lowered and the lead is applied to the die and bent and formed, the surface where the die and the punch are in contact with the lead, in other words, the surface where the die and the punch face each other (hereinafter, referred to as a processing surface) ) Rubs the solder plating of the lead, and a part of the solder plating adheres to the processing surface of the die or punch.

[0007] This adhesion accumulates during repeated molding,
Unevenness occurs on the processing surface of the die or punch, and the flatness (coplanarity) of the lead bending and the bending (skew) of the leads in the parallel direction deteriorate. this is,
The same can occur in the method shown in FIG.

In IC / LSI, both coplanarity and skew are required to be 100 μm or less, and in the future, lead pitch will be further miniaturized, so that stricter accuracy will be required.

In order to prevent such deterioration in accuracy, the processing surface of the die or punch is cleaned with a gold brush or a metal spatula every several thousand to 50,000 shots so that the lead shape can be maintained. The solder attached to the die and the punch is difficult to clean, and in some cases, the die or the punch must be removed from the apparatus. In addition, Ra is arithmetic mean roughness Ra defined by JISB0601.

[0010]

In order to solve the above problems, the present inventors have proposed a tool such as a die and a punch as described in Japanese Patent Application Laid-Open No. 7-212842. This example is shown in FIG. 8 and FIG. In this proposal, a diamond or diamond-like carbon film is formed on a processing surface of a die or a punch by a vapor phase synthesis method, so that solder plating does not easily adhere to the processing surface. Further, the surface roughness of the processed surface is set to 0.08 μm Ra or less so that a deposit of solder plating is hardly generated.

As described above, the diamond film formed on the base material by the vapor phase synthesis method has a very small thickness. It is not so difficult to polish this film to have a surface roughness of 0.08 μm or less, but pinholes may be generated on the polished surface, and further polishing is required to remove this. Required. However, this pinhole has a size of about 20 μm, and the film thickness of diamond is very thin as described above. Film thickness may be required.

A diamond thin film is formed on a cemented carbide or ceramic material as a base material by a vapor phase synthesis method.
Since the CVD process is performed at a high temperature, there is a possibility that the film is peeled off when the laminated film thickness is increased due to the difference between the coefficient of thermal expansion of the base material and the coefficient of thermal expansion of diamond.

The present invention has been made to solve the above problems, and it is possible to obtain a die and a punch to which solder plating does not easily adhere when bending a lead and to grind the pin and the hole until the pinhole can be removed. It is possible to propose a die and a punch that can solve the above problems in the manufacturing process.

[0014]

A first feature of the lead frame bending die according to the present invention is that in a lead frame bending die of a solder plating, the die has a raised portion on an upper surface of the die, and the raised portion has a raised portion. On the outside and at least the portion facing the punch, the surface roughness of the machined surface is 0.1 mm.
A vapor-phase synthetic diamond chip finished to not more than 08 μmRa is joined, and the vapor-phase synthetic diamond chip is integrally combined with a die body formed of a conductor.

As a second feature, the vapor-phase synthetic diamond chip is joined to a substrate that is divided from the die body, and the substrate is integrally combined with the die body.

A first feature of the lead frame bending punch of the present invention is that, in the solder plating lead frame bending punch, at least a portion facing the die has a surface roughness of 0.08 μm Ra. A vapor-phase synthetic diamond chip finished below is joined, and the vapor-phase synthetic diamond chip is integrally combined with a punch body.

As a second feature, the vapor-phase synthetic diamond chip is joined to a base material that is separated from the punch body, and the base material is integrally combined with the punch body.

A further feature is that the above-mentioned die and punch are combined to provide a tool for bending a solder-plated lead frame.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The lead frame bending die according to the present invention has a raised portion formed on the upper surface of a die body made of SKD steel, cemented carbide, or the like. It is attached with an adhesive or an adhesive. When joining by brazing, the base material is Mo, W, cemented carbide, Si which is close to the thermal expansion coefficient of the diamond tip.
Such as ₃ N _4, ceramics such as SiC are suitable. When bonding with an adhesive, there is no problem as long as the adhesive has heat resistance enough to withstand the polishing heat generated when polishing the diamond chip, and the base material is not particularly limited, but in consideration of corrosion resistance, SUS440C or the like is used. Stainless steel can also be used.

The above-mentioned vapor-phase synthetic diamond chip is provided at least in a portion facing the punch and hitting the lead when the lead frame is processed. Since the vapor-phase synthetic diamond chip is provided with a thickness of 300 to 500 μm, even if a pinhole is generated when the processed surface is polished, it can be polished again and does not become a defective product.
Here, the surface roughness of the processed surface is set to 0.08 μmRa or less, more preferably 0.03 μmRa or less so that deposits such as solder are not generated.

Further, it is more effective to join the diamond chip to a base material that is divided from the die body and to combine the base material and the die body integrally in terms of simplifying the manufacturing process. As described above, the polishing margin for removing the processed surface of the diamond chip by polishing differs depending on the occurrence state of the pinhole. In such a case, in order to fit the overall size of the die to the finished dimensions, it is only necessary to make the base material large and adjust it based on the diamond surface when polishing is completed, so problems such as dimension breakage also occur do not do.

Further, in such a split type structure, when the lead sliding portion of the die is worn, it can be repaired by re-polishing. The dimension removed by the re-polishing can be inexpensively dealt with by rebuilding the die body or building up the plating on the base material side.

The diamond tip is non-conductive, and static electricity generated by friction during lead processing cannot be released through the diamond tip. Therefore, it is necessary to form the die body with a conductive material. As described above, when the diamond chip is attached to the substrate that is separated from the die body, it is possible to release static electricity at the contact portion between the die body and the lead, and the substrate does not need to be a conductive material. .

In the lead frame bending punch of the present invention, a vapor-phase synthetic diamond chip is joined to the punch body by brazing or an adhesive. In the case of joining by brazing, as the base material, Mo, W, cemented carbide, ceramics such as Si ₃ N ₄ , SiC or the like having a coefficient of thermal expansion close to that of a diamond chip is suitable. When bonding with an adhesive, there is no problem as long as the adhesive has heat resistance enough to withstand the polishing heat generated when polishing the diamond chip, and the base material is not particularly limited.
Stainless steel such as 440C can also be used.

The above-mentioned vapor-phase synthetic diamond chip is provided at least at a portion facing the die and at the time of contact with the lead during processing of the lead frame. Since the vapor-phase synthetic diamond chip is provided with a thickness of 300 to 500 μm, even if a pinhole is generated when the processed surface is polished, it can be polished again and does not become a defective product. Here, the surface roughness of the processed surface is set to 0.08 μmRa or less, more preferably 0.03 μmRa or less so that deposits such as solder are not generated.

As in the case of the die, it is more effective to join the diamond chip to the base material separated from the punch body and to combine this base material with the punch body in terms of simplifying the manufacturing process. . As described above, the polishing margin for removing the processed surface of the diamond chip by polishing differs depending on the occurrence state of the pinhole. In such a case, in order to fit the size of the entire punch to the finishing dimensions,
Since the base material may be made larger and adjusted at the completion of polishing with reference to the surface of the diamond, there is no problem such as cutout of dimensions.

Further, in such a split type structure, when the lead sliding portion of the punch is worn, it can be repaired by re-grinding similarly to the die.
The dimension removed by the re-polishing can be handled at low cost by plating the base material or remanufacturing the die body.

Since static electricity generated by friction during lead processing is released from the die body, the punch does not necessarily need to have conductivity, and the material of the punch body can be appropriately selected.

Various techniques have been proposed as a method for producing a vapor-phase synthetic diamond chip of the present invention. However, a method of forming a diamond layer on a substrate such as silicon by a vapor-phase synthetic method and dissolving the substrate is used. A mother disk with a size of about 50 x 1t is commercially available from De Beers or Norton. There is a method such as performing required chip removal with a laser or the like from this mother disk. Sex is very high.

Further, even if a chip is generated at a corner or an edge during polishing of a diamond chip, if the size of the chip is within the range of the thickness of the diamond chip, the chip is removed by additional polishing. It becomes possible.

[0031]

(Embodiment 1) As a first embodiment of the present invention,
The die is shown in FIG. 1 and the punch is shown in FIG. The die body 6 and the punch body 8 are machined into a shape as shown in FIGS. 1 and 4 using a cemented carbide as a material, and a diamond chip 7 having a thickness of 300 μm is joined thereto by brazing. A raised portion 15 is formed on the upper surface of the die body 6, and is processed into a concave shape for bonding the diamond chip 7 to the outside thereof. By processing according to the size of the diamond chip 7, the bonding is performed accurately. be able to. The processing surface of the diamond chip 7 is polished in advance and finished without pinholes. This is because, in the case of a die body having a shape as shown in FIG. 1, the protrusion 15 on the upper surface of the die body 6 interferes with a grindstone or the like. Is difficult.

As a result of manufacturing the die and the punch by the above-described method, there was no pinhole on the processing surface of the die and the punch, and it was possible to easily manufacture a high-precision die and a punch. The shape of the processing surface of the diamond chip 7 is not limited to a flat surface as in the present embodiment, and a shape having an R-shaped corner portion on the processing surface as shown in FIGS. Can be given as an example.

(Embodiment 2) As a second embodiment of the present invention, a die is shown in FIG. 3 and a punch is shown in FIG. In these, a part of the base material where the die body 6 or the punch body 8 and the diamond chip 7 are joined is divided. First, the die substrate 9 and the punch substrate 10
Is processed into a shape as shown in the figure, and a concave portion for bonding the diamond chip 7 is formed on the upper surface thereof. At this time, the dimensions of the die substrate 9 and the punch substrate 10 in the height direction (vertical direction in the figure) are slightly larger than predetermined dimensions. Next, a diamond chip 7 having a thickness of 300 μm is bonded to the concave portion, and the diamond chip 7 is ground and polished to finish it into a predetermined shape. Polishing of the processed surface of the diamond chip 7 is performed until pinholes are eliminated. Finally, the bottom surfaces of the die substrate 9 and the punch substrate 10 are ground with reference to the processing surface of the diamond chip 7, and the overall size of the die substrate 9 and the punch substrate 10 to which the diamond chip 7 is bonded is determined. Finish to dimensions. The die body 6 or the punch body 8
And fixed with screws.

With the above divided structure, the die substrate 9 and the punch substrate 10 can be easily manufactured, and the die body 6 and the punch body 8 can be repeatedly used, which is economical. . In addition, diamond chip 7
Is worn out, the diamond chip 7 can be reused if it is removed from the die base material 9 and the punch base material 10 and joined to another die base material 9 and the punch base material 10 and processed into a predetermined shape. .

Comparative Example As a comparative example for the present invention,
The die and punch shown in FIGS. 8 and 10 were manufactured. The die substrate 9 and the punch substrate 10 were processed into predetermined dimensions, and a diamond thin film was formed on the upper surfaces of these by a vapor phase synthesis method. The thickness of this thin film was about 20 μm. As a result of polishing the diamond thin film, 13 out of 100 holes had pinholes, and the 13 holes were polished again. However, there are some with large pinholes, and eight substrates were exposed during repeated polishing,
These became defective products.

[0036]

As described above, since the diamond chip of the vapor phase synthesis is provided on the processing surface of the die and the punch of the present invention, even if a pinhole is generated when the processing surface is polished, it is re-used. Polishing is possible, and even if a chip is generated in a corner portion or an edge portion during polishing, the chip can be removed by additional polishing, so that a defective product does not occur. In addition, since the diamond chip can be processed and then joined, the polishing can be easily performed, and the versatility is very high.
Furthermore, by joining the part to which the diamond chip is joined to the base material separated from the die or punch body, the body can be used repeatedly, and the diamond chip can be reused by repolishing.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a die of the present invention.

FIG. 2 is a perspective view showing another embodiment of the die of the present invention.

FIG. 3 is a perspective view showing still another embodiment of the die of the present invention.

FIG. 4 is a perspective view showing an embodiment of the punch of the present invention.

FIG. 5 is a perspective view showing another embodiment of the punch of the present invention.

FIG. 6 is a perspective view showing still another embodiment of the punch of the present invention.

FIG. 7 is a perspective view showing an example of a conventional die.

FIG. 8 is a perspective view showing an improved example of a conventional die.

FIG. 9 is a perspective view showing an example of a conventional punch.

FIG. 10 is a perspective view showing an improved example of a conventional punch.

FIG. 11 is a conceptual diagram illustrating a method for forming a gull-wing type lead.

FIG. 12 is a conceptual diagram illustrating a method of forming a DIP lead.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Punch 3 Pressure pad 4 Lead 5 LSI mold body 6 Die body 7 Diamond chip 8 Punch body 9 Die base material 10 Punch base material 11 Die contact surface (work surface) 12 Punch contact surface (work surface) 13 Screw 14 diamond thin film 15 ridge

Claims (5)

[Claims] 1. A die for bending a solder-plated lead frame, wherein the die has a raised portion on its upper surface, and at least a portion facing the punch outside the raised portion has a rough surface of a processed surface. A vapor-phase synthetic diamond chip finished to 0.08 μm Ra or less is joined, and said vapor-phase synthetic diamond chip is integrally combined with a die body formed of a conductor. Die. 2. The method according to claim 1, wherein the vapor-phase synthetic diamond chip is joined to a base material that is separated from the die body, and the base material is integrally combined with the die body. Die. 3. A solder-plated bending punch for a lead frame, wherein at least a portion facing the die is bonded with a vapor-phase synthetic diamond chip having a processed surface having a surface roughness of 0.08 μm Ra or less. A punch for bending a lead frame, wherein a vapor-phase synthetic diamond chip is integrally combined with a punch body. 4. The punch according to claim 3, wherein said vapor-phase synthetic diamond chip is joined to a base material divided from said punch body, and said base material is integrally combined with said punch body. punch. 5. A lead frame processing tool, wherein a die according to claim 1 or 2 and a punch according to claim 3 or 4 are combined to bend a lead frame that has been plated with solder.