JPH0650360U - Lead frame for semiconductor device - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To prevent the adhesive such as paste from flowing out while suppressing the interference of the inner leads with the array area and maintaining stable support of the pads. [Constitution] In a lead frame in which a support bar 4 is protruded outward integrally with a pad 2 for mounting a semiconductor chip, a portion where the support bar is connected to the pad is a wide planar head 8, and a width is formed on an upper surface of the head. A groove 8a that crosses the direction or a partially recessed recess is provided. When the adhesive for fixing the semiconductor chip to the pad 2 is directed to the support bar side, the frictional resistance on the head acts largely and the flow is cut off by the recess. Since the pad 2 is supported by the wide head 8, the recess 8 is formed in this head.
Even if a is provided, the strength is compensated and stable pad support becomes possible. Further, since only the tip of the support bar 4 is widened, the interference with the area of the adjacent inner leads 5 is small.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a lead frame for a semiconductor device, and to a lead frame structure for preventing an adhesive such as a paste for fixing a semiconductor chip from flowing out from a pad to a support bar side.

[0002]

[Prior art]

 A lead frame used for assembling a semiconductor device is formed by patterning inner leads and outer leads around a pad on which a semiconductor chip is placed, and a typical plan view of the lead frame is shown in FIG. Shown in.

In the figure, a strip-shaped thin metal plate is used as a material, and a lead frame pattern is formed in a region excluding the side rails 1 at both ends by pressing or etching. The lead frame pattern is centered on the pad 2, and the semiconductor chip 3 is mounted and fixed on the upper surface of the pad 2 using a die bonding paste.

The pad 2 having a quadrangular planar shape is supported at its corners by four support bars 4. These support bars 4 are integrally extended from the side rails 1 and support by receiving loads from the pads 2 and the semiconductor chip 3.

A large number of inner leads 5 are arranged around the pad 2, and the tip portions of the inner leads 5 are all in the posture of facing the pad 2. Further, a large number of outer leads 6 which are continuous with the inner leads 5 and extend outward are formed as a part of the pattern. A tie bar 7 is provided at a boundary portion between the inner lead 5 and the outer lead 6 so as to connect adjacent lead portions. When the semiconductor chip 3 and the inner lead 5 are wire-bonded with each other and then packaged with a resin or plastic encapsulant, the tie bar 7 stops the encapsulation burr and connects the leads to maintain the space between them and prevent deformation. To prevent.

The semiconductor chip 3 mounted on the pad 2 and the inner lead 5 are connected by wire bonding. Due to this connection, the semiconductor chip 3 must be positioned on the pad 2 with high accuracy and maintained in a stable fixed state. For this reason, various semiconductor chip 3 fixing structures have been conventionally used, but as described above, for example, there is a method of bonding to the upper surface of the pad 2 using a paste.

However, when such a paste is used, the paste is likely to flow out when a heat treatment for adhesion is performed after coating. In this case, since the pad 2 is connected to the support bar 4, the softened paste tries to spread around the support bar 4 through the support bar 4. If the paste squeezes out in this way, there is a risk that it may cause an obstacle during resin encapsulation or affect the stable fixing of the semiconductor chip 3.

To address such a problem, for example, in Japanese Patent Laid-Open No. 60-62143, the support bar 4 is detoured in a curved shape instead of a straight shape at the boundary between the support bar 4 and the pad 2. A configuration is disclosed in which a planar shape is provided and a protrusion is provided in the detour portion in the width direction. Further, Japanese Patent Laid-Open No. 2-303057 discloses a support bar 4 having a recess on the upper surface of the tip thereof.

By providing these protrusions and depressions, the paste that is about to flow out from the pad 2 can be received like a weir, and the semiconductor chip 3 can be stably fixed.

[0010]

[Problems to be solved by the device]

 However, if the support bar 4 has a planar shape that bypasses the tip portion, it interferes with the planar space occupied by the tip portions of the inner leads 5 arranged adjacent to the support bar 4. For this reason, the gap between the inner leads 5 and the like will be further reduced as the number of pins increases as in recent years, and the processing problem will increase.

In addition, if the tip of the support bar 4 is provided with a recess, it does not interfere with the range of the inner lead 5. However, since the thickness of the recess is thin, it is unavoidable that the support of the pad 2 is weak in strength. Therefore, there is a possibility that the pad 2 may vibrate during wire bonding between the semiconductor chip 3 and the inner lead 5, resulting in a bonding error.

As described above, in the conventional structure, although the flow-out of the paste can be prevented, there still remain problems such as interference with the inner leads and a reduction in the pad supporting strength in the case of multiple pins.

The problem to be solved in the present invention is to prevent the adhesive material such as the paste from flowing out while suppressing the interference of the inner lead with the array area and maintaining the stable support of the pad.

[0014]

[Means for Solving the Problems]

 The present invention comprises a pad for mounting and fixing a semiconductor chip on the upper surface with an adhesive for bonding, a support bar protruding outward from the pad for supporting the pad, and an inner lead having a tip facing the pad. A lead frame having rows and a head having a planar shape wider than the support bar is formed at a portion where the support bar is connected to the pad, and the entire length in the width direction is formed on the upper surface of the head. Alternatively, it is characterized in that a recess is provided in a part thereof.

[0015]

[Action]

 When the adhesive on the pad softens due to heating etc., a small amount will flow out through the support bar connected to the pad. At this time, since the wide head is directly connected to the pad, the contact area of the adhesive also becomes large, and the flow is suppressed by the frictional resistance. In addition, the adhesive is dropped into the concave portion provided in the head to interrupt the flow. Therefore, the adhesive is prevented from flowing out toward the support bar.

Since the pad is supported by the support bar through the wide head, even if the head is provided with a concave portion, the decrease in strength thereof can be compensated by the length in the width direction, and the pad can be stably supported.

[0017]

【Example】

 FIG. 1 is a plan view showing a main part of a lead frame of the present invention, which is an enlarged view of a portion corresponding to the pad shown in FIG. 4 and a region around the tip of the inner lead.

In the figure, the pad 2 has four support bars 4 protruding from the corners thereof, and the tips of the inner leads 5 are arranged so as to face the periphery thereof. The outer lead and other patterns are exactly the same as those shown in FIG. 4, and the support bar 4 is integrated with the outer side rail.

At the tip of the support bar 4 integrated with the corner of the pad 2, a head 8 having a width about twice as large as that of other portions is provided. As shown in the enlarged view of FIG. 3A, the head 8 has a width gradually increasing from the tip of the support bar 4 and its end is integrated with the corner of the pad 2. Further, on the upper surface of the head 8, there is provided a single groove 8a as a recess, which crosses in the width direction. This groove 8a can be obtained by simultaneously pressing and recessing or forming a notch or the like when press-forming the pattern of the lead frame from the material.

Here, when the semiconductor chip 3 is placed and fixed on the pad 2 as described with reference to FIG. 4, a paste is applied as an adhesive to the upper surface of the pad 2. This paste is applied to at least the entire area of the lower surface of the semiconductor chip 3.

The semiconductor chip 3 is adhered and fixed to the paste by heating, and at this time, a part of the paste is softened and flows out to the outside of the pad 2. Such a paste flows out toward the support bar 4 integrated with the pad 2 and covers the upper surface of the head 8.

Since the head 8 is wide in the width direction, when the paste from the pad 2 side is received, the frictional resistance due to the large area is used to reduce the fluidity of the paste. Further, when the paste flows into the groove 8a, the paste becomes a recess, so that the paste needs a force to crawl upward from the groove 8a in order to move outward from the groove 8a. Therefore, the resistance of the surface of the head 8 and the interruption of the flow by the groove 8a are possible, and the outflow of the paste toward the support bar 4 is suppressed.

It should be noted that the amount of paste flowing out is limited, and the flow does not result in the entire groove 8a being filled at the same time. Therefore, it is always possible to interrupt the flow of the paste by setting the groove 8a to have an appropriate depth and utilizing the size of its inner volume due to its wide width.

In this way, the flow out of the paste from the pad 2 can be stopped by the head 8 portion, and a sufficient paste remains on the pad 2. Therefore, the semiconductor chip 3 can be stably fixed on the pad 2, and subsequent processing such as wire bonding can be performed well.

Since the head 8 is provided with the groove 8a and the thickness thereof is partially thinned, the width of the head 8 is wide, so that the strength reduction due to the groove 8a can be compensated by the wide width. Therefore, the force for supporting the pad 2 by the four support bars 4 is not attenuated, and the pad 2 can be stably held. Therefore, the vibration and swing of the pad 2 at the time of wire bonding or the like can be suppressed, and the processing can be performed with higher accuracy.

Further, since the head 8 is only provided by widening the width of the tip portion of the support bar 4, the range in which it interferes with the arrangement region of the tip portion of the inner lead 5 can be small. For this reason, even with the multi-pin specification, there is no obstacle to the miniaturization of the inner leads 5 and the reduction of the intervals between them.

In the embodiment, the concave portion is the single groove 8a that crosses the head 8 in the width direction, but it may be a plurality of grooves, or a part of the region included in the head 8 may be partially depressed. It may be good.

[0028]

[Effect of device]

 In the present invention, the adhesive is prevented from flowing out from the pad, the semiconductor device can be stably fixed on the pad, and the accuracy of wire bonding with the inner lead is improved. Further, even if the concave portion is provided, the width of the head is wide, so that the pad can be supported with sufficient strength, the vibration does not occur in the pad during the wire bonding and other processes, and the processing accuracy is further improved. Furthermore, since only the tip of the support bar is widened, it does not interfere with the arrangement of the tips of the inner leads, and can be sufficiently applied to a multi-pin lead frame.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing an embodiment of a lead frame of the present invention.

FIG. 2 is a vertical sectional view taken along the line AA of FIG.

3A and 3B are details of the head, in which FIG. 3A is an enlarged plan view thereof, and FIG. 3B is a vertical sectional view taken along the line BB of FIG. 3A.

FIG. 4 is a plan view showing a general pattern of a lead frame.

[Explanation of symbols]

 1 Side Rail 2 Pad 3 Semiconductor Chip 4 Support Bar 5 Inner Lead 6 Outer Lead 7 Tie Bar 8 Head 8a Groove (Concave)

Claims (1)

[Scope of utility model registration request] 1. A pad for mounting and fixing a semiconductor chip on an upper surface with an adhesive for bonding, a support bar projecting outward from the pad to support the pad, and an inner lead having a tip facing the pad. In a lead frame having rows, a head having a planar shape having a width wider than that of the support bar is formed in a portion where the support bar is continuous with the pad, and an entire length or a width in the width direction is formed on an upper surface of the head. A lead frame for a semiconductor device, characterized in that a recess is provided in the portion.