JPH06275755A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To provide a novel manufacturing method of a lead frame which does not involve enlargement of a scale of a device and can reduce an operational time while maintaining strain stress removal operation which is equal to that of a conventional method wherein a thermal treatment process is adopted. CONSTITUTION:A lead frame 10 wherein a number of inside leads 11, a connection piece 12 for connecting an area near a tip part of the inside leads 11, a chip mounting pad 14, etc., are formed by press processing is mounted on a pedestal 60 and is transferred at a specified velocity. A polishing and cleaning material consisting of a number of glass particles of fine diameter are sprayed toward an inside lead 11 of each unit frame 10a in the lead frame 10 to remove strain stress, burr and lubricant remaining in the inside lead 11. The connection piece 12 is removed after the treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame for a semiconductor device, and more particularly to a 42 alloy (iron-N).
(i alloy), Cu, etc., after forming a large number of internal leads and connecting pieces on a plate-shaped substrate by press working, the present invention relates to a processing step of removing strain stress and the like generated in these internal leads.

[0002]

2. Description of the Related Art Heretofore, as a method of manufacturing a lead frame of this type, there has been known a method of adopting a heat treatment step for removing strain stress and the like after press working (for example, Japanese Patent Laid-Open Publication No. Sho.
59-72754). Further, with respect to the formation of the inner lead and the connecting piece, a press work is generally adopted in which a work of punching a predetermined portion of the base material is repeatedly performed.

The above-mentioned conventionally known press working will be described in more detail with reference to FIG. 9. In the drawing, 100 is a base material immovably supported by a die 200 and a stripper 201, and 202 is a die.
A punched hole opened in 200, 203 is a through hole opened in the stripper 201 with the same width as the punched hole 202, 204
Is a punch having a size that can be inserted into the through hole 203. By punching a predetermined position of the base material 100 with the punch 204, a plurality of inner leads 1 can be held while maintaining a constant spacing 101.
It is designed to form 02.

By the way, when the inner lead 102 is formed by such a processing means, the punched spacing is
Upper half portion 10 of the side surface of 101 (that is, the side surface of the inner lead 102)
Whereas 3 is a sheared surface, the lower half portion becomes a fractured surface, and the fractured surface portion remains as a burr 110. In addition, punch 20
Bending moment is applied by the punching and drawing operations of 4 and the inner lead 102 is tilted, and
Strain stress remains in 102. Further, since the punching and pulling operations of the punch 204 are repeated, the adjacent inner leads 102 are inclined in opposite directions.

As a processing means for suppressing the above-mentioned burrs and inclinations, the split vertical punching method shown in FIGS. 2 to 5 has been conventionally known. According to this method, the occurrence of burrs and inclinations can be almost suppressed, but residual strain stress has not been completely eliminated. The divisional upper and lower punching method will be described in detail in the section of Examples.

[Problems to be Solved by the Invention]

Burr, tilt, and
The residual strain stress or the like becomes a factor such as insulation failure due to contact between the internal leads 102 or bonding failure with a chip.
Occurrences of these insulation defects and bonding defects tend to increase with the recent trend toward more compact semiconductor devices and increased pin count, resulting in increased density near the tips of the internal leads 102. Removal becomes more important.

However, in the conventional stress relieving means adopting the above-mentioned heat treatment step, since the furnace and the heat source for the heat treatment are required, the apparatus becomes large in size and a considerable work is required for heating. There is a problem in that productivity is lowered because time is spent.

The present invention has been made in view of such conventional circumstances, and an object thereof is to obtain a stress relieving effect equivalent to that of a conventional method employing a heat treatment process and to increase the size of the apparatus. It is an object of the present invention to provide a novel manufacturing method that is free from the risk of causing this and can shorten the working time.

[0009]

In order to achieve the above-mentioned object, a method of manufacturing a lead frame according to the present invention is provided with a large number of internal leads for electrically connecting to a semiconductor chip and the tips of the internal leads. A method for manufacturing a lead frame for a semiconductor device, which comprises: forming a connecting piece for connecting portions near each other by press working, removing strain stress remaining in the internal lead, and removing the connecting piece after the treatment. In the above, the strain stress removing process is a process of spraying a polishing / cleaning material composed of a large number of fine glass particles onto the inner lead at a low pressure.

[0010]

According to the above-mentioned means, the inclination of the internal lead is corrected and residual strain stress is removed without damaging the lead surface by the peening effect obtained by spraying a large number of fine glass particles at a low pressure. The same effect as the conventional heat treatment process is obtained. The fine glass particles can be sprayed by using, for example, a well-known spraying device having an injection nozzle at the tip, and the stress removal by the spraying can be achieved in an extremely short time. Further, by spraying the fine glass particles, the burr generated by the press working and the lubricant used for the press working are removed at the same time, and the burr removing step and the degreasing step as a post step can be omitted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the lead frame manufacturing method according to the present invention will be described below. First, the base material of the lead frame 10
Band-shaped ultra-thin metal plate that becomes 10 '(eg 42 alloy plate, Cu
1) and a plurality of internal leads 11 and a connecting piece 12 for connecting the vicinity of the tips of the internal leads 11 to a plate or the like).
Then, press working is performed so as to form a lead frame shape that leaves the chip mounting pads 14 supported by the four leg pieces 13.

The pressing process includes a primary process shown in FIG. 2, a secondary process shown in FIG. 3, and a tertiary process shown in FIG. 2 (1
In the next step), 10 'is a base material that is immovably supported by the die 20 and the stripper 30, 21 is a bite hole formed in the die 20, and 31 is a hole wider than the bite hole 21 in the stripper 30. The through hole 40 is a punch having a size that can be fitted into the through hole 31, and the substrate 1 is lowered by lowering the punch 40.
Spacing at 0'15 Recess on upper half of punching position 1
6 is formed, and the lower half side thereof is projected downward with a width dimension smaller than that of the recess 16 so as to be bitten into the biting hole 21. At this time, the lower limit of the punch 40 is set to the position shown in FIG. After the punch 40 is pulled out and the stripper 30 is removed, the projecting portion 17 is pushed out from the bite hole 21 by the compressed air supplied from the pressurizing means 50 which is connected to the bite hole 21.

In FIG. 3 (second process), FIG.
The base material 10 'processed into the above shape as described above is placed on another die 22 having no bite hole and pressed in the thickness direction by a flat punch 32, as shown in FIG. Protruding part
Push 17 in the direction of recess 16. At this time, the protruding portion 17 and the recess
Shear on both the left and right sides of the part between 16 and scrap 18
The spacing 15 is formed in the state in which is left. In addition, the ends of the sheared portions in the above-mentioned primary process and secondary process are sagged.
18a, which is the side of spacing 15 (ie, the inner lead).
11 side surface), but since the peripheral surface is spherical, there is no risk of adverse effects later.

In FIG. 4 (third step), the pressurizing means in which the substrate 10 'processed as described above is sandwiched between the die 23 and the stripper 33 and communicated with the through hole 24 provided in the die 23. 51
The scrap 18 remaining in the spacing 15 is pushed out of the mold by the compressed air supplied from.

By repeating the above first to third steps, a large number of internal leads 11 having a predetermined width are formed in parallel while maintaining a constant spacing 15, as shown in FIG. A connecting piece 12 for connecting the vicinity of the tip of the lead 11 is formed, and a lead frame 10 in which a plurality of unit frames 10a shown in FIG.

According to such a press working method,
Pressing pressure is applied separately from the upper side in the next step and from the lower side in the secondary step, so that the formed internal leads 11 have a sheared surface on their side surfaces, and the occurrence of burrs is almost completely suppressed. Moreover, the bending moment applied to the inner lead 11 becomes uniform in the vertical direction, the occurrence of tilt is almost suppressed, and the strain stress remaining in the lead 11 becomes extremely small.

Next, the residual strain stress in the inner lead 11 in each unit frame 10a of the lead frame 10 manufactured by the above-mentioned press working is removed. In this step, as shown in FIGS. 6 and 7, the pedestal 60 on which the lead frame 10 manufactured in the previous step is moved and moved in the length direction, and the unit frame 10a in the lead frame 10 to be transferred is moved. The abrasive cleaning material 70 consisting of a large number of fine glass particles is sprayed at low pressure toward the internal leads 11 of the, and the peening effect obtained by this results in the same strain as the conventional heat treatment process without scratching the surface of the leads 11. Get the stress relief effect.

A specific example of the transfer speed of the lead frame 10 is about 20 to 70 mm / sec, and the spraying pressure of a large number of fine glass particles is 1 kg / cm ² or less.
Perform at a low pressure of about 0.6 kg / cm ² . Further, a shock absorbing sheet 61 made of a cushioning material such as rubber is laid on the mounting surface of the lead frame 10 on the receiving table 60 to protect the lower surface of the lead frame 10.

The fine glass particles are sprayed by using a well-known spraying device having a spray nozzle 80 at the tip. A plurality of injection nozzles 80 are installed, if necessary, with injection angles θ ₁ and θ ₂ and heights h ₁ and h ₂ that can spray fine glass particles over the entire area where the internal leads 11 are formed in the unit frame 10a.

Removal of the strain stress by spraying such fine glass particles at a low pressure can be achieved in an extremely short time, that is, by moving the lead frame 10 once, and at the same time, lubrication used for press working. The agent is removed. Also,
The removal of burrs and the correction of inclination caused by the press working shown in FIG. 9 described in the section of the prior art are also performed by spraying fine glass particles several times, that is, the transfer of the lead frame 10 is repeated 2-3 times. The effect can be obtained with.

Finally, the connecting piece is removed by a known cutting process to obtain a lead frame 10 in which a plurality of unit frames 10b shown in FIG. 8 are arranged in parallel.

Incidentally, as an example of the dimensional relationship of the lead frame manufactured by the manufacturing method of the present invention, w (internal lead width) = e (spacing between leads) = t (plate thickness) ×
It becomes α, and α is generally set to about 1.0 within the range of 1.2 to 0.7. Further, t ₁ shown in FIG. 2 (the lower limit of the punch in the primary step of press working) is t (plate thickness) × 1/3,
C (dimension difference between the concave portion 16 and the protruding portion 17) shown in FIG.
It is about 4 to 6% of (plate thickness). Furthermore, the diameter of each fine glass particle in the abrasive material is w (internal lead width) x 1 /
Approximately 2 to 1/4.

Therefore, when a substrate having a t (thickness) of 0.15 mm is used, w (internal lead width) and e (spacing between leads) are about 15 mm to 0.12 mm and t ₁ (press working). Of 1
The punch lowering limit in the next step) is about 0.05 mm, c (the size difference between the concave portion 16 and the protruding portion 17) is about 0.006 to 0.009 mm, and the diameter of each fine glass particle is 0.03 to 0.05 mm (30 to 50 μm).
m).

The pressing process is not limited to the split top and bottom punching method shown in FIGS. 2 to 5, and a more general pressing method described in the section of the prior art may be adopted. In this embodiment, the split vertical punching method is adopted to prevent burrs and tilts from occurring, and the residual degree of the strain stress is suppressed as much as possible, so that the strain stress can be removed by spraying the polishing and cleaning material in a very short time, that is, This can be done by carrying out the transfer of the lead frame 10 shown in 6 once. In addition, when the general pressing method is adopted, the transfer of the lead frame 10 is repeated 2-3 times, but in this case, the initial purpose is sufficiently achieved.

Further, the shape and dimensional relationship of the unit frames in the lead frame 10, the number and position of the jet nozzles installed,
The transfer means of the lead frame 10 and the like are not limited to those described above. For example, the lead frame has a shape in which the connecting piece 12 is formed integrally with the chip mounting pad 14, or the injection nozzle.
It goes without saying that changes within a well-known range, such as providing 80 so as to be movable along the outer peripheral edge of the chip mounting pad 14, are optional.

[0026]

Since the method of manufacturing the lead frame according to the present invention is configured as described above, the residual strain stress in the inner lead generated by the press working which is a pre-process thereof is well known by the injection nozzle. Using the apparatus, it can be removed in an extremely short period of time in the same manner as the conventional heat treatment process. Therefore, it is possible to provide a novel manufacturing method which is capable of reducing the working time while maintaining the strain stress removing action equivalent to that of the conventional method which employs the heat treatment step, without causing the size of the apparatus to increase.

In addition, by spraying fine glass particles, the burrs generated by the press working and the lubricant used for the press working are removed at the same time, which eliminates the need for a burr removing step and a degreasing step as a post-step. As a result, there are many effects such as downsizing of the device and further shortening of working time.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a lead frame shape, showing a state before cutting a connecting piece.

FIG. 2 is a vertical sectional view showing a primary step of press working.

FIG. 3 is a vertical sectional view showing a secondary step of press working.

FIG. 4 is a vertical cross-sectional view showing a third step of press working.

FIG. 5 is a vertical cross-sectional view showing a process of forming internal leads by repeating press working.

FIG. 6 is a perspective view showing a step of spraying fine glass particles.

FIG. 7 is a front view of the same section.

FIG. 8 is a plan view showing an example of a lead frame shape, showing a state after cutting the connecting piece.

FIG. 9 is a vertical cross-sectional view showing a conventionally known general press working.

[Explanation of symbols]

10: Lead frame 11: Inner lead 12: Connection piece 14: Chip mounting pad 15: Spacing 60: Cradle 70: Abrasive cleaning material consisting of many small glass particles 80: Jet nozzle

Claims (1)

[Claims] 1. A large number of internal leads for establishing electrical continuity with a semiconductor chip and a connecting piece for connecting the vicinity of the tips of the internal leads are formed by press working and then remain in the internal leads. In a method for manufacturing a lead frame for a semiconductor device, which comprises removing strain stress and removing the connecting piece after the treatment, the strain stress removing process is performed by using an internal lead made of a large number of fine glass particles. A method of manufacturing a lead frame, characterized in that the step of spraying the lead frame at a low pressure.