JPH04324970A - Manufacture of semiconductor device lead frame - Google Patents

Abstract

PURPOSE:To prevent large burrs from occurring locally by a method wherein the corners of a tie bar and a dam section, a tie bar, and the corner R of an outer lead are punched out in a tie bar blanking process in the fabrication of a lead frame in such a manner that an upper die punch and a lower die cutting edge are positioned at a right angle with the corner R. CONSTITUTION:The corners of a tie bar and a dam section, a tie bar, and the corner R of an outer lead are punched out at A and B through such a manner that a lower die cutting edge 9 and an upper die punch 8 cutting edge are positioned at a right angle with a tangential line of the R section in a tie bar blanking process. In such a relation between a lead frame and a die (punch and die), when a frame is cut, a cutting process takes place uniform throughout the punch 8 and the die 9, so that the cut area of the frame is kept uniform in state after the frame is cut. Burrs occur uniform along the cut area and large burrs hardly occur, so that a lead frame can be enhanced in yield.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tie bar removal process in the manufacture of lead frames for semiconductor devices.

0002

[Background Art] With the demand for smaller size and higher performance of electrical equipment, semiconductor devices (ICs) are required to produce high-mix low-volume products and shorten delivery times. Lead processing is a process after IC mold resin encapsulation. (Removal of unnecessary resin waste from the dam part, removal of tie bars, removal of outer periphery, and bending) are manufactured using an integrated automatic assembly line. FIG. 2 shows a conventionally used IC lead frame. FIG. 3 shows the lead frame after molding with resin. 1 is a molded package, 2 is a tie bar, 3 is an internal lead, 4 is an external lead, 5 is an outer frame, and 6 is a dam portion (unnecessary resin). In the process of manufacturing IC lead frames (pressing products or etching products), two tie bar parts,
The radius of the corner part of the dam part in Figure 6 is machined within the minimum possible limit during machining (abrasion and life of the mold used for frame machining (not shown), and its management, etc.). R shape like 7 (R=0.1~0.2
mm).

FIG. 5 shows a structural diagram of a tie bar cutting die (upper die, lower die). Reference numeral 8 indicates an upper die punch, and 9 indicates a lower die cutting edge (die side).

FIG. 6 shows the positional relationship between the frame and the die (die and punch) when punching out the tie bar portion of the lead frame.

The tie bar punch 8 of the upper die has a dimension slightly smaller than the dam part dimension of the frame (0.0 mm on one side) in consideration of the amount of resin shrinkage during resin molding of the mold package 1 and the amount of change in tie bar pitch. 03~0.05m
In order to perform the processing in step m), punching is performed while being positioned at the R portion of the frame dam portion 7.

[0006] The cutting phenomenon in normal punching is that burrs 14 are formed on the dam part 11, cut surface 12, and fracture surface 13 as shown in FIG.
is occurring.

[0007]

[Problems to be Solved by the Invention] However, in the tie bar removal process of lead frame processing described above, since the R portion of the dam portion 7 is cut, burrs are generated.
There is a problem in that the appearance of To explain the occurrence of this burr, as shown in FIG. 7, the die 9 is located at the R position of the dam part 7 of the frame, and the clearance is approximately 0.0.
The punch 8 is positioned with a gap of 1 mm. At this time, the cutting phenomenon when cutting the frame dam part 7 is as follows.
Tensile stress and compressive stress of C are generated in the A direction part and it is cut, but part of the B direction part becomes free,
As the punch 8 enters, it becomes torn downward by the die and punch. For this reason, large burrs (burrs 14 during cutting) are generated downward. This generated burr becomes a burr state in the direction of the tie bar in the subsequent process (solder plating, bending process) and short-circuits with the adjacent frame, causing a defect.

[0008] Another problem was that the appearance of the product was not good.

The present invention eliminates the above-mentioned problem of large burrs that occur when cutting the R portion of the tie bar of a frame during lead processing (tie bar extraction process), and eliminates product defects due to burrs. The purpose of this invention is to provide an excellent device for removing tie bars.

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a method for removing corners of tie bar parts and dam parts (unnecessary resin parts), corners of tie bar parts, and corners of external leads in the tie bar removal process of lead frame processing. A means is provided for punching out the R part of the part so that the cutting edges of the upper die and the lower die are positioned at right angles.

[0011]

[Function] As mentioned above, in the lead processing (tie bar removal process), the dam part side (unnecessary resin part) located at the tie bar part of the lead frame and each corner part of the external lead part are removed from the frame R. A method of punching by positioning the lower die and upper punch, which are the cutting edges, at right angles to the part (material).
Since the tie bar cutting die was used, the occurrence of burrs becomes uniform, and the occurrence of large localized burrs, which was the case in the past, is eliminated.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.

The positional relationship between the frame and the mold (lower die 9, upper punch 8) when punching out the tie bar portion 2 of the lead frame is shown.

The die cutting edge 9 of the lower die and the cutting edge of the upper die punch 8 are applied to the corner portion 7 of the tie bar portion 2 and the dam portion 6 (unnecessary resin portion), and to the R portion which is the corner portion of the external lead 4. A shape in which the blade is located perpendicular to the tangent of the R part (A in the figure,
(as shown in B). A frame and type like this (
The cutting phenomenon (relationship between tensile stress and compressive stress) when cutting the frame occurs almost uniformly between the punch 8 and the die 9.
All the frame cut surfaces after cutting will be in a uniform state.

[0015]

Effects of the Invention As explained above, in lead processing (tie bar removal process), each corner of the dam part side (unnecessary resin part) located at the tie bar part of the lead frame and the external lead part is removed from the frame R part. By using a punching method (tie bar cutting die) in which the lower die and upper punch, which are the cutting edges, are positioned at right angles to the (material), the occurrence of burrs (burrs) becomes uniform, and some parts like before. It was possible to eliminate the occurrence of large localized burrs. By eliminating the occurrence of large burrs, an improvement in yield can be expected.

[Brief explanation of drawings]

[Fig. 1] Illustration of an embodiment of the present invention

[Figure 2] Lead frame configuration diagram

[Figure 3] Lead frame after molding resin

[Figure 4]
R part explanatory diagram

[Figure 5] Structure diagram of tie bar removal die

[Figure 6] Positional relationship diagram between frame and mold

[Figure 7] Diagram explaining the occurrence of burrs

[Figure 8] Diagram explaining the burr situation

[Explanation of symbols]

2 Tie bar part 4 External lead 6 Dam section 7 Corner part 8 Punch 9 Die

Claims (1)

[Claims] Claim 1: In the tie bar cutting process in the lead frame processing process of semiconductor devices, the dies of the upper punch and the lower punch, which are tie bar cutting dies, are inserted into the dam part side and the external lead located in the tie bar part of the lead frame. 1. A method for manufacturing a lead frame for a semiconductor device, which has a cutting section positioned perpendicular to a side R-shaped portion, and cuts a tie bar with the punch.