JP3015550B2 - Semiconductor device lead frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a QFP (Quu
ad Flat Package) or SOP (S
The present invention relates to a lead frame of a semiconductor device applied to a mall outline package.

[0002]

2. Description of the Related Art FIG. 1 shows a lead frame of a semiconductor device applied to a conventional QFP. In the lead frame 10, a substantially square island 11 on which a semiconductor chip (not shown) is provided is connected to an outer frame 13 by tie bars 12 provided at four corners. A plurality of outer leads 14 are provided around the island 11, and one ends of these outer leads 14 are connected by a dam bar 15 for preventing resin from flowing out during resin molding. The other end of the outer lead 14 is connected by an outer lead connecting bar 16, and the outer lead connecting bar 16 is connected to the outer frame 13 by a connecting bar 17. Further, the outer frame 13 is provided with a pilot hole 18 used for transporting and positioning the lead frame 10.

[0003]

However, the lead frame of the above-mentioned conventional semiconductor device has a small thickness of 0.15 mm, and may be deformed in an assembly process from die bonding to lead forming. In particular, in the wire bonding step and the molding step, the lead frame is easily deformed because thermal stress is applied to the lead frame.

That is, in the wire bonding step, first, the lead frame is heated on the preheater frame. At this time, the lead frame is deformed into a convex shape due to thermal stress. Thereafter, when the lead frame is transported under the frame retainer of the bonding apparatus, the semiconductor chip may collide with the frame retainer and be damaged. In addition, when the lead frame is transported after the bonding is completed, the semiconductor chip and the metal wiring may collide with the frame retainer and be damaged, thereby lowering the yield.

On the other hand, in the molding process, the current thermal expansion coefficient of the molding resin is 42 alloy (Fe-42% Ni alloy).
And smaller than the Cu alloy, but closer to the Cu alloy. Therefore, the mold resin shrinks,
When the molding is completed, the larger the mold resin is, the more stress is exerted when the resin contracts, and the lead frame is pulled and the frame is deformed. This tendency is remarkable in the case of 42 alloy. FIG. 2 shows a deformed state of the frame after the completion of the molding. The lead frame 21 is vertically deformed with respect to the mold resin 22.

[0006] The deformation of the lead frame also affects the subsequent trim forming process of the outer lead. That is, when the lead frame is deformed, the position of the pilot hole 18 provided in the outer frame 13 of the frame is shifted from a predetermined position. For this reason, when the pilot hole 18 is used as a position detection and conveyance means, the position detection and conveyance cannot be performed normally. Even if the position detection and conveyance can be performed, since the frame is deformed, in a so-called Po process for cutting the dam bar 15, a portion deviated from a position to be originally cut is cut, and an undercut is performed. (Bite-in).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to prevent deformation of a lead frame due to thermal stress or stress when resin shrinks, and to convey it during bonding. While improving performance,
An object of the present invention is to provide a lead frame of a semiconductor device which can prevent undercut of an outer lead.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a mounting portion on which a semiconductor chip is mounted,
A first connecting portion having one end provided at a corner of the mounting portion;
A straight portion, and both ends of the straight portion are connected to an outer frame, and the other end of the first connecting portion is orthogonally connected to a substantially central portion of the straight portion. A second connecting portion having a width smaller than that of the first connecting portion;
And a plurality of outer leads
Third connection for integrally connecting the other ends of the outer leads
In parallel with the third connecting portion via the fourth connecting portion.
Connected to the outer frame via a fifth connecting portion.
A sixth connecting portion which is connected and has a width smaller than that of the third connecting portion;
And

[0009]

[0010]

According to the present invention, the width of the first connecting portion provided at the corner of the mounting portion on which the semiconductor chip is mounted is larger than the width of the first connecting portion having both ends connected to the outer frame. A narrow second connection is provided. Therefore, when a thermal stress or a stress at the time of resin shrinkage is applied to the lead frame, the second connecting portion is deformed, so that the entire lead frame can be prevented from being deformed.

Also, the outer frame is connected in parallel to a third connecting portion integrally connecting the other end portions of the plurality of outer leads via a fourth connecting portion and a fifth connecting portion. And a sixth connecting portion having a width smaller than that of the third connecting portion. Therefore, when thermal stress or stress at the time of resin contraction is applied to the lead frame, the second connecting portion is deformed and the third connecting portion is deformed, so that the entire lead frame can be more reliably prevented from being deformed.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

In a lead frame 30 shown in FIG. 3, a substantially square island 31 on which a semiconductor chip (not shown) is provided has tie bars 32 at four corners. The tip of the tie bar 32 is connected to the center of a support bar 33 orthogonal to the tie bar 32. This support bar 33
Is narrower than the tie bar 32, and both ends thereof are connected to an outer frame 36 via connecting portions 34 and 35.

A plurality of outer leads 37 are provided around the island 31.
One end of 7 is connected by a dam bar 38 for preventing resin from flowing out during resin molding. The other end of the outer lead 37 is connected by an outer lead connecting bar 39, and the outer lead outer connecting bar 41 is connected to the outer lead connecting bar 39 by a plurality of connecting bars 40 in parallel. The outer lead outer connecting bar 41 is narrower in width than the outer lead connecting bar 39, and is connected to the outer frame 36 by a plurality of connecting bars 42. Furthermore, the outer frame 36 is provided with a pilot hole 43 used for transporting and positioning the lead frame 30.

In the above configuration, when the lead frame 30 is heated in the wire bonding step and a thermal stress is applied to the lead frame 30, or when the resin contracts and the stress is applied to the lead frame 30 in the molding step. The narrow support bar 33 and the outer lead outer connecting bar 41 are deformed. Therefore, the thermal stress applied to the lead frame 30 is absorbed by the support bar 33 and the outer lead outer connection bar 41, and the lead frame 30 is prevented from being deformed in a direction perpendicular to the surface thereof. Therefore, when the lead frame is carried, the semiconductor chip mounted on the lead frame does not collide with the frame holder, so that the yield can be improved.

Further, since the lead frame 30 is not deformed, the position of the pilot hole 43 does not shift. Therefore, the transport performance of the lead frame can be improved, and the undercut of the outer lead can be prevented in the Po process. FIG. 4 and FIG.
This is a modification of FIG. 3, and the same parts as those in FIG. 3 are denoted by the same reference numerals, and only different parts will be described.

[0017] In FIG. 4, the connecting portions 34a, 35 a is
The support bar 33a is longer than the connecting portions 34 and 35 shown in FIG. 3, and the support bar 33a is shorter than the support bar 33 shown in FIG.

In FIG. 5, the support bar 33b
Is longer than the support bar 33 shown in FIG. 3, and the connecting portions 34 and 35 shown in FIG. 3 are omitted. That is, both ends of the support bar 33b are directly connected to the outer frame 36. 4 and 5, the same effects as in the embodiment shown in FIG. 3 can be obtained.

FIGS. 6 to 8 show a comparison between the structure of the present invention and the conventional structure. In FIG. 6, the first embodiment is different from the lead frame of the present invention shown in FIG.
mm 42 alloy, tie bar 3
2, the width of the outer lead connecting bar 39 is 0.5 mm.
6mm, the width of the support bar 33 orthogonal to the tie bar 32 is
0.3mm, width of outer lead outer connecting bar 41 is 0.2mm
Is the case. The second embodiment is the same as the first embodiment except that the material is different from that of the first embodiment.

In Comparative Example 1, the conventional lead frame shown in FIG. 1 was manufactured from a 42 alloy having a thickness of 0.15 mm, and the width of the outer lead connecting bar 16 was the same as in Examples 1 and 2. Comparative Example 2 has the same conditions as Comparative Example 1 except that the material is different from Comparative Example 1. In each of Examples 1 and 2 and Comparative Examples 1 and 2, 100 lead frames having the same configuration were manufactured, and the following measurement was performed.

FIG. 7 is a diagram showing a case where a semiconductor chip is bonded to each of the lead frames manufactured under the conditions shown in Examples 1 and 2 and Comparative Examples 1 and 2 and then heated on a wire bonder. It shows the result of measuring the amount of deformation by an eddy current sensor and the transfer failure rate during wire bonding. One lead frame is provided with four islands, and a semiconductor chip is bonded to each island. As is clear from FIG. 7, in Examples 1 and 2, the amount of deformation was small with respect to the thermal stress, and therefore, no transport failure occurred.

FIG. 8 shows the amount of deformation of the frame when the above-described bonded lead frame is molded with, for example, resin KE-300TS-1, and the percentage of undercut defects after the Po process. The defect rate of the undercut was determined to be defective when cut into the state as shown in FIG. 9A, and as non-defective when it was as shown in FIG. 9B. As is clear from FIG. 8, in Examples 1 and 2, the amount of deformation of the frame due to the shrinkage of the resin was small, so that no undercut defect occurred. In the case of the present invention, the deformation of the lead frame can be prevented regardless of the material of the lead frame. Note that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention.

[0023]

As described above in detail, according to the present invention, deformation of the lead frame is prevented from thermal stress and stress when the resin contracts, the transfer performance at the time of bonding is improved, and the outer lead is formed. A lead frame of a semiconductor device capable of preventing undercut can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part showing a lead frame of a conventional semiconductor device.

FIG. 2 is a side view showing a state in which a lead frame of a conventional semiconductor device is resin-molded.

FIG. 3 is a configuration diagram of a main part showing one embodiment of the present invention.

FIG. 4 is a configuration diagram of a main part showing a modification of FIG. 3 ;

FIG. 5 is a configuration diagram of a main part showing a modification of FIG. 3 ;

FIG. 6 is a diagram showing the implementation conditions of the lead frame of the present invention and a conventional semiconductor device.

FIG. 7 is a diagram showing a deformation amount and a transfer failure rate of a lead frame of a semiconductor device of the present invention and a conventional semiconductor device due to thermal stress.

FIG. 8 is a diagram showing a deformation amount due to resin shrinkage of a lead frame of the present invention and a conventional semiconductor device and an undercut defect rate.

FIG. 9A shows an undercut defect, and FIG. 9B shows a non-defective product.

[Explanation of symbols]

30, lead frame, 31 island, 32 tie bar, 33, 33a, 33b support bar, 34, 3
5 ... connecting part, 36 ... outer frame, 37 ... outer lead, 39
... outer lead connecting bar, 41 ... outer lead outer connecting bar, 40, 42 ... connecting bar.

Claims (1)

(57) [Claims] 1. A mounting portion on which a semiconductor chip is mounted, a first connecting portion having one end provided at a corner of the mounting portion, and a linear portion. Are connected to the outer frame, and the other end of the first connecting portion is connected to the substantially linear portion at right angles to the center of the linear portion. The second connecting portion is narrower than the first connecting portion. A plurality of outer leads having one end integrally provided around the mounting portion, and a third portion integrally connecting the other ends of the outer leads.
And a third connecting portion, which is connected in parallel to the third connecting portion via a fourth connecting portion, is connected to the outer frame via a fifth connecting portion, and has a width larger than that of the third connecting portion. And a sixth connecting portion having a narrow width.