JP3048480B2 - Lead forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead forming method in a lead processing step among semiconductor manufacturing steps.

[0002]

2. Description of the Related Art Generally, after a molding process, a deburring process, and a soldering process are completed, a semiconductor package is cut into individual pieces from a long lead frame in a lead processing process, and a peripheral edge of each semiconductor package is cut. Is formed into a predetermined shape.

FIG. 4 is a view for explaining an example of a lead forming method in a lead processing step. First,
In FIG. 4, reference numeral 20 denotes an upper die, and 21 denotes a lower die. Among them, the upper die 20 is provided with a punch 22 and a knockout 23, and the lower die 21 is provided with a die 24. When performing lead forming, the semiconductor package 25 cut into individual pieces is set on the die 24 of the lower die 21 as shown in FIG. When the upper die 20 descends from this state, the knockout 23 first comes into contact with the lead 26 on the periphery of the semiconductor package 25 and the spring 27
The lead 26 is sandwiched between the die 24 and the die 24 by the elastic force of the above. When the upper die 10 is further lowered, each lead 26 is sandwiched between the punch 22 and the die 24 and formed into a predetermined shape as shown in FIG.

[0004]

When removing resin burrs attached to the lead frame surface in the above-described deburring step before lead processing, pressure is applied to the lead frame by high-pressure injection of an aqueous solution or the like. This may cause variations in the height of the tip of the lead at the periphery of the package. However, in the above-described conventional lead forming method, the lead on the package periphery is formed into a predetermined shape in a state where the height of the lead tip remains uneven. The variation in the height of the bottom surface of the leads is reflected in the variation in the height of the bottom surface, and this variation in the height of the bottom surface of the lead causes soldering failure when the manufactured semiconductor device is surface-mounted on a mounting surface such as a substrate. I was For this reason, conventionally, a lead inspection process or a lead correction process is provided after forming a lead into a predetermined shape, and this has been dealt with. However, in this case, a great increase in the number of work steps is caused. Did not.

Some of the conventional lead forming methods aim at flattening the lowermost surface of the lead by forming the lead into a predetermined shape and then, for example, uniformly pressing each lead from above. However, even with this, it was not possible to eliminate the influence of the variation in the height of the lead tip.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has as its object to provide a lead forming method capable of suppressing variations in the height of the lowermost surface of a lead after forming.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and a first aspect of the present invention relates to a lead forming method for bending a plurality of leads extending from a semiconductor package into a predetermined shape . Using a mold,
A fulcrum is a portion of the lead near the semiconductor package.
Then, the lead is separated from the semiconductor package.
By applying a pressing force to the bent end,
Above or below, the bending angle in the given shape
A first step of performing a bending process at an angle smaller than
The lead is bent into the predetermined shape by using a die.
And a second step of working.

[0008]

In the lead forming method of the present invention,
The multiple leads extending from the semiconductor package
When bending into a shape, first
Upward or downward, the bending angle is
By performing bending in the range of 2 to 5 degrees, spring
Insufficiency of correction due to backing
Without applying strong stress, the height of the lead
Rack is corrected, and then the bending is performed on the lead.
Bend at a bending angle larger than the angle
Of the height of the lowermost surface of the lead
Variation is suppressed. In addition, the other read-form of the present invention.
In the semiconductor package
When bending multiple leads into a predetermined shape
First, the portion of the lead near the semiconductor package
As a fulcrum, from the semiconductor package in the above lead
Applying a pressing force to the remote end
Without any pinching, and with very little force
The variation in the height of the lead tip is corrected by
By bending the lead into a predetermined shape, the lead
Variations in the height of the lowermost surface can be suppressed.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of the lead forming method according to the present invention. In FIG. 1, reference numeral 1 denotes a semiconductor package, and a plurality of leads 2 extend at a predetermined pitch around the periphery of the semiconductor package 1. Here, FIG. 1A is a plan view (upper side) and a side view (lower side) showing a package state before forming. In this state, the height of the lead end of the package periphery varies as shown in the figure. It is assumed that W has occurred.

In the lead forming method of this embodiment,
First, as shown in FIG. 1 (b), the semiconductor package 1
The plurality of extended leads 2 are bent at a predetermined angle θ with respect to a horizontal plane . The bending angle of each lead 2 obtained by this is approximately 2 to 3 degrees is sufficient. However, in order to obtain this bending angle, considering the springback of the lead 2 when it is once bent and then opened, The predetermined angle θ needs to be about 5 °. If the angle θ is set too small, the height of the tip of the lead returns to the original position due to the springback, and conversely, the angle θ
Is set too large, when the lead 2 is bent, a strong stress may be applied to the semiconductor package 1 to cause a package crack or the like. Therefore, it is desirable that the angle θ be kept to the minimum necessary.

After all the leads 2 have been bent at a predetermined angle θ, the lead 2 on the package periphery is connected to the lead 2 shown in FIG. Forming into a predetermined shape as shown in FIG. At this time, the final bending shape of the lead 2 is
Because of the crank shape, the final bending (for
The bending angle of the lead in (Ming) is about 90 °.
The lead bending method employed here may be, for example, a lead bending method using a cam or a lead bending method using a roller (not shown) other than the method using the press die shown in FIG. May be adopted.

As described above, in the lead forming method according to the present embodiment, first, the plurality of leads 2 extending from the periphery of the package are bent downward at a predetermined angle θ to correct the variation W in the height of the lead tips. Is done. As a result, the heights of the tips of the leads 2 are evenly aligned,
By forming the lead 2 into a predetermined shape from this state, variations in the height of the lowermost surface F of the lead are suppressed, and more accurate lead forming is realized.

Incidentally, in an experiment conducted by the present applicant, when a lead was formed into a predetermined shape without bending as in the conventional method, the lead floated from the reference surface (mounting surface) was 81.2 μm on average, and the standard deviation was In the case where the lead was formed into a predetermined shape after being bent as in the present example instead of 15.2 μm, the above-mentioned values were 38.0 μm on average and 9.8 μm in standard deviation, and a remarkable effect was obtained. confirmed.

Here, specific means for bending the lead 2 at a predetermined angle θ will be described. In the present embodiment, as shown in FIG. 2, the lead 2 extending on the peripheral edge of the semiconductor package 1 is bent at a predetermined angle using the upper die 3 and the lower die 4. First, a punch 5 is attached to the upper die 3, and the punch 5 has a concave portion 6 for avoiding collision with the semiconductor package 1 and a pressing surface 7 inclined at a predetermined angle. On the other hand, a die 8 is attached to the lower die 4, and a concave portion 9 for avoiding contact with the semiconductor package 1 and a lead support surface 10 substantially parallel to the pressing surface 7 are formed on the die 8. Have been.

When the lead 2 is bent by using the upper die 3 and the lower die 4 having the above-described structure, first, the semiconductor is placed on the lower die 4 while the lead 2 is placed on the lead support surface 10 formed on the die 8. Set package 1. Then, when the upper mold 3 is lowered from that state, the leads 2 on the package periphery are sandwiched between the lead support surface 10 of the lower mold 4 and the pressing surface 7 of the upper mold 3 as shown in FIG. Thereby, all the leads 2 are bent at a predetermined angle. At this time, in order to bend each of the leads 2 uniformly, it is preferable that the lead support surface 10 of the lower die 4 is in proper contact with the fixed end of the lead 2 (the root of the semiconductor package 1).

By the way, in the above-described lead bending means, since the lead 2 is completely sandwiched from above and below, a large pressure is applied to the surface of the lead 2 and there is a concern that the solder on the surface of the lead 2 may be peeled off. . As a countermeasure for this, as shown in FIG.
One of the lead support surfaces 10 of the mold 4 (for example,
The pressing surface 7) is connected to the free end side of the lead 2, that is, the semiconductor package.
Formed so as to contact the end remote from the die 1 and the other end (eg,
For example, the lead support surface 10) of the lower mold 4 is fixed to the fixed end of the lead 2.
Side, that is, in contact with the vicinity of the semiconductor package 1.
To bend the lead 2 to a predetermined angle.
When the semiconductor package 1 is near the lead 2
With the side part (the contact part of the lead support surface 10) as a fulcrum,
End of lead 2 remote from semiconductor package 1
(Lead tip). In this way, when the upper die 3 is lowered to press the pressing surface 7 and the lead support surface 10 against the leads 2 as shown in FIG. 3, both ends of each of the leads 2 are parallel in size. Since two forces having the same and opposite directions, that is, couples P1 and P2 are applied, it is necessary to completely pinch the lead 2 as described above.
In addition , the lead 2 can be bent to a predetermined angle with a very small force, thereby eliminating the fear of solder peeling.

In the lead forming method of the above embodiment, when the lead 2 is bent at a predetermined angle, the lead 2 is bent downward. However, the bending direction of the lead 2 in the present invention is limited to only the downward direction. Instead, even if the lead is bent upward at a predetermined angle, the variation in the height of the lead tip is corrected, and the same effect as described above can be obtained.

In this embodiment, the type of semiconductor device to be handled is QFP (Quad Flat Pa).
Cage) type is described as an example, but the lead forming method of the present invention is based on SOP (Small Ou).
line Package) type, Q
FJ (Quad Flat J-leaded Pac)
Kage) type and SOJ (Small Outlin)
The same effect can be obtained even when the present invention is applied to the case of handling other surface mount type semiconductor devices such as an e-J-leaded Package) type.

[0019]

As described above, according to the present invention,
Extending from semiconductor package according to the forming method
When bending multiple leads into a predetermined shape
First, upward or downward with respect to a plurality of leads,
Bending angle is 2 to 5 degrees with respect to the horizontal plane
To correct the lack of correction due to springback.
Inviting or stressing semiconductor packages
Without any variation in the height of the lead tip.
Wear. And then, the bending angle with respect to the lead
Bend at a larger bending angle and place the lead in place.
By adjusting the shape, the height of the lead
I can suppress the luck. This reduces the bending angle
The tip of the lead is too high due to the springback
Situations such as not being able to fully correct for variations in
Conversely, it is strong in semiconductor packages because the bending angle is too large
For example, package cracks may occur due to stress.
Make the height of the bottom surface of the lead uniform without inviting situations
Becomes possible. Also, other lead forming of the present invention
According to the method, a plurality of resources extending from a semiconductor package are provided.
When bending a lead into a predetermined shape, first
With the vicinity of the semiconductor package in the fulcrum as a fulcrum,
At the end of the above lead away from the semiconductor package
Applying a pressing force completely sandwiches the lead surface
End of the lead
The height variation can be corrected. And that
After that, the lead is bent into a predetermined shape.
The variation in the height of the lowermost surface of the lead can be suppressed.
You. This causes the solder to peel off on the surface of the lead
The height of the bottom surface of the lead
It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of a lead forming method according to the present invention.

FIG. 2 is a view for explaining a lead bending means.

FIG. 3 is a diagram for explaining another bending means of the lead.

FIG. 4 is a diagram for explaining an example of a lead forming method.

[Explanation of symbols]

 1 semiconductor package 2 lead

Claims (2)

(57) [Claims] In a lead forming method for bending a plurality of leads extending from a semiconductor package into a predetermined shape, a first die is used to form the semiconductor package on the leads.
With the vicinity of the package as a fulcrum,
Applying a pressing force to the end remote from the semiconductor package
By the above or below with respect to the lead,
Bending at an angle smaller than the bending angle for a given shape
Using a first step of performing a second mold, song said lead to said predetermined shape
And a second step of shaping. 2. The method according to claim 1, wherein the bending angle in the first step is water.
The angle is in the range of 2 to 5 degrees with respect to the plane.
The lead forming method according to claim 1.