JP3495566B2 - Semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which an island is omitted and the external dimensions can be reduced.

[0002]

2. Description of the Related Art The most popular technique for sealing a semiconductor device is a transfer molding technique for sealing the periphery of a semiconductor chip with a thermosetting epoxy resin. A lead frame is used as a support material for the semiconductor chip, the semiconductor chip is die-bonded to the island of the lead frame, the bonding pad and the lead of the semiconductor chip are wire-bonded with a wire, and the lead is placed in a mold having a desired outer shape. It is manufactured by setting a frame, injecting epoxy resin into a mold, and curing it.

On the other hand, the wave of miniaturization and weight reduction for various electronic devices is unavoidable, and semiconductor devices incorporated therein are also required to have higher capacity, higher functionality and higher integration. Therefore, a technique that has existed as an idea for a long time (for example, Japanese Patent Laid-Open No. 55-1111517) has attracted attention as a technique for encapsulating a plurality of semiconductor chips in one package, and there has been a movement to realize the technique. That is, the first semiconductor chip is fixed on the island, the second semiconductor chip is fixed on the first semiconductor chip, and the corresponding bonding pad and lead are connected by a bonding wire and sealed with resin. It is a thing.

Although this structure increases the cost, it is possible to realize a light, thin and short structure by integrating a plurality of chips. Therefore, rather than the DIP type package having a large outer dimension, there is a strong intention to store it in a surface mount type and thin type package, and this has a great advantage as a whole. However, since it is necessary for the semiconductor chip to have a certain degree of mechanical strength as a support substrate for the circuit element formed on its surface, at least about 200 μm is required.
A certain degree of thickness is essential, and it is desired that the resin has a thickness of at least about 200 μ above the semiconductor chip in terms of the moisture resistance of the semiconductor device and the loop height of the bonding wire. Incorporating all the thicknesses required for manufacturing and stacking two or more chips results in an increase in the external dimensions of the resin, which does not fit into the external dimensions of the conventionally prepared package. There was a drawback to say. Furthermore, such as molds and test measuring equipment,
Most of the manufacturing equipment used in the subsequent process has to be designed differently, and there is a drawback that the cost increase becomes extremely large due to the capital investment.

Therefore, Japanese Patent Application No. 9-55174 (filed on Mar. 10, 1997), FIG. 5, FIG. 6 (cross-sectional view taken along line AA of FIG. 5) and FIG. 7 (BB of FIG. 5). (A cross-sectional view taken along the line), the island 22 on which the semiconductor chips 20, 21 are mounted
It has been announced that the lead and the island are stepped so that the back surface of the resin is exposed on the surface of the resin 23, and a plurality of semiconductor chips are stacked on the island to reduce the height of the resin.

Further, since the warp of the package occurs due to the difference in thermal expansion coefficient between the island 22 and the resin 23, the island size has been reduced. That is, FIG. 5 is a plan view of the first chip 2 on the island 22.
0, a second chip 21 is provided thereon, and the first and second chips 20 and 21 are provided with lead terminals 24 ... It is electrically connected. Further, by extending the tie bars 26a, 26b, 27a and 27b from the respective corners of the island 22 and integrating them with the lead frame,
Supports islands and prevents twisting during molding.

[0007]

Here, the island 22
When fixing the first semiconductor chip 20 with the insulating adhesive 28, the adhesive is applied to the island 22, and the semiconductor chip is placed and pressed to fix the semiconductor chip. However, the thickness of the island and the thickness of the adhesive are factors that still increase the thickness of the sealing resin.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and firstly, a second semiconductor is provided at a position corresponding to one side pair opposed to the other side pair. Paying attention to the fact that the chip projects outward from the first semiconductor chip to form a non-overlapping portion, and the first support lead is applied to the back surface of the second semiconductor chip corresponding to the projecting non-overlapping portion. The two-story chips are brought into contact with each other and supported by the support leads. For example, if the lower first semiconductor chip and the supporting lead have substantially the same thickness, the first supporting lead is
The second semiconductor chip can be supported without protruding from the back surface of the first semiconductor chip, and the thickness of the conventional island can be omitted.

Secondly, by disposing the first support leads in the vicinity of each of the four parts, the two-story chip can be stably supported without twisting. Third
In the second structure, 2 located on the other side
This is to be solved by providing a second support lead, which is located near the other side of the U-shaped bottom, between the first support leads of the book. Since the first support lead is thin and mechanically weak, it is difficult to hold the semiconductor device after molding. However, by providing the second support lead, the mechanical strength can be increased.
Further, if the resin is placed right next to the resin injection hole of the mold, the resin flow comes into contact with the second support lead, and the resin can be poured into a narrow portion which is a non-overlapping portion of the second semiconductor chip. .

Fourth, the problem is solved by replacing the first support lead with a U-shaped lead and bringing the bottom portion into contact with the back surface of the second semiconductor chip which is the non-overlapping portion. is there.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described in detail below with reference to FIG. In the figure, 50, 5
Reference numeral 1 denotes a first semiconductor chip and a second semiconductor chip, respectively. First
And on the silicon surface of the second semiconductor chips 50, 51,
Various active and passive circuit elements are formed in the previous process,
Further, a bonding pad 52 for external connection is formed on the peripheral portion of the chip. The bonding pad 5
2 to cover the silicon nitride film, the silicon oxide film,
A passivation film such as a polyimide insulating film is formed, and the upper portion of the bonding pad 52 is opened for electrical connection.

The second semiconductor chip 51 is fixed on the passivation film of the first semiconductor chip 50 with an insulating adhesive, here an epoxy adhesive.
Here, the first semiconductor chip 50 and the second semiconductor chip 5
1 has different sizes, and at least the left and right sides of the second semiconductor chip 51 project from the sides of the first semiconductor chip 50 to form a non-overlapping portion. That is, the back surface corresponding to the left and right sides of the second semiconductor chip 51 and the vicinity thereof is a space without the first semiconductor chip 50.

According to the present invention, the support leads are arranged in the non-overlapping space, and the support leads are used instead of the islands. Specifically, first, the first support leads 59a, 59b, 60a, 6 are formed on the left and right sides of the second semiconductor chip 51, particularly in the regions located near the four corners.
0b is to be placed. Here, in order to reduce the number of sheets in the drawing, two types of support leads are shown as the support leads 59a and 59b on the right side and the support leads 60a and 60b on the left side.
In fact, it is better that the four support leads are unified.

The support lead on the right side is formed to have a wide width by entering the sealing resin from the outside, but the width may be the same.
Further, in order to prevent lateral movement of the chip, the chip may be brought into contact with the side edge of the first semiconductor chip 50. Further, the left side support lead enters the sealing resin from the outside to have a wide width, and is bent into an L shape at the non-overlap portion. Also, like the support lead on the right side, they may have the same width,
It may be brought into contact with the side edge of the first semiconductor chip 50.

Here, the support leads only need to support a two-story semiconductor chip, and one support lead may be provided on each side.
It may be supported by three on one side and two on the other side. Further, in the present application, the number is four, but more may be supported. Here, the second support lead 70 is provided between the left and right support leads. The support lead is provided to support the strength of the first support lead.
That is, after being molded, the lead terminals are cut and bent into a predetermined shape while supporting the semiconductor device with the support leads. However, since the first support leads are thin, a second support lead 70 is separately provided. The support strength is increased. If the bottom T side surface of the second support lead is arranged right next to the resin injection hole of the mold, the injected resin comes into contact with the side surface and divides the flow into two sides, the back side and the front side with respect to the paper surface. , Also shows the function of allowing resin to be satisfactorily poured into the space of the non-overlapping portion. Further, the width of the support lead becomes narrower when it comes out of the sealing resin, in order to prevent intrusion of water or the like.

Next, the support lead shown in FIG. 2 will be described. Similar to FIG. 1, the left 70a, which shows two types on the right and left, will be described first. U-shaped support lead 70 on the left side
In FIG. 3A, the second support lead 70 of FIG. 1 is extended to the non-overlapping portion of the second semiconductor chip 51. This enhances the support strength of the two-story chip before molding, and further supports the strength of the support leads 59a, 59b, 60a, 60b after cutting and bending of the lead terminals after molding. Right side second support lead 71
Shows only an example in which the U-shape is changed to a straight line, and three or more pieces may be provided on the side edge.

Further, the support lead and the second semiconductor chip 51.
An adhesive is applied to the back surface in consideration of mutual fixation. However, it may not be applied. This is because the support lead only needs to support the chip, and the double-layered chip can be supported by the bonder jig even during bonding. When wire bonding is completed, the chip can be supported by wires.

In any of the types shown in FIGS. 1 and 2, the support lead extends on the back surface of the second semiconductor chip 51 located in the non-overlapping portion, so that there is an effect that a separate island need not be provided. . Further, by forming the thickness of the support lead to be equal to or thinner than the thickness of the first semiconductor chip 50, the support lead is prevented from being exposed from the sealing resin. FIG. 3 shows a cross-sectional view taken along the line AA of FIG. 1, and if the support lead has a thickness equal to or smaller than the thickness of the first semiconductor chip 50, the back surface of the support lead including the thickness of the adhesive resin is included. The resin of a certain thickness will be covered.

Next, one end of a bonding wire 56 such as a gold wire is wire-bonded to the bonding pad 52 on the surface of the semiconductor chips 50 and 51, and the other end of the bonding wire 56 is the tip of a lead terminal 57 for external lead-out. It is wire-bonded to the portion 57a. With this, each bonding pad 52 and each lead 57 are electrically connected.

The main parts including the semiconductor chips 50 and 51, the tip portions 57a of the lead terminals, and the wires 56 are packaged by molding the periphery with an epoxy thermosetting resin 58. Similar to the conventional drawings shown in FIGS. 6 and 7, the lead terminal 57 is led to the outside from a position on the side wall of the package that is approximately half the thickness of the resin 58. The lead terminal 57 led out of the resin 58 is bent downward at one end, and is bent again to form a Z-shape. The forming shape is such that the back side fixed portion of the lead terminal 57 is adhered to the conductive pattern formed on the printed circuit board so as to face it.
It is a shape for surface mounting applications. Here, the lead terminals extend to the upper and lower sides in both FIGS. 1 and 2, but may extend to the upper, lower, left, and right sides. In this case, the U-shaped support lead is omitted and the pad is connected to the pad of the second semiconductor chip 51 via a wire.

Further, as described in the conventional example, the lead 57 and the support lead are stepped so that the back surface of the first semiconductor chip 50 is exposed on the surface of the resin 58, and the conventionally used island is omitted and supported. By placing the leads in the non-overlapping space, the height of the resin was greatly reduced. The support leads from the four directions are integrated with the lead frame to prevent twisting during molding.

To briefly explain the manufacturing method, first, the supporting leads provided at the four corners in the state of the lead frame are subjected to step processing so that the height of the semiconductor chip surface to be placed and the tip 57a of the lead terminal is adjusted. The first and second semiconductor chips 50 and 51 are arranged at substantially the same position, and the first and second semiconductor chips 50 and 51 are adhered to the support lead with an adhesive insulating material, and the bonding pad 52 is formed.
And the tip portion 57a of the lead terminal are wire-bonded.

Next, the frame body of the lead frame and the lead terminal 57 are sandwiched and fixed by the upper and lower molds so that the two-story semiconductor chip supported by the supporting leads and the wires is located in the cavity provided in the upper and lower molds. It can be obtained by injecting and curing the resin in such a state. The lead frame is formed by etching or punching a copper-based or iron-based plate-shaped material having a plate thickness of 150 to 200 μ to mold each part such as the support lead and the lead terminal 57. After the molding step, Until cut, each part is held by the frame of the lead frame.

The tip portion 57 of the lead terminal in the held state
The heights of a and the frame body are the same, and only the supporting leads are stepped to have different heights. That is, it is bent upward inside the resin 58, extends substantially horizontally again at a position corresponding to the height of the lead 14, and the cut surface is exposed at the surface of the resin 58 and terminates. Each semiconductor chip 50, 51 is
Immediately before the assembly process, the back surface is polished by a back grinding process to a thickness of 250 to 300 μ. Lead terminal 5
The plate thickness of No. 7 is about 130μ. Since the support leads are formed simultaneously from the plate-shaped material, the plate thickness of the support leads has the same value, and this value is a limit value at which the mechanical strength of each part is maintained.

In the present invention, the island is omitted, and molding is performed so that the back surface of the first semiconductor chip 50 is exposed on the surface of the resin 58, so that the resin has a sufficient thickness.
Further, when the lead frame is set in the cavity, it can be obtained by placing the back surface of the first semiconductor chip in contact with the cavity surface of the lower mold and sealing with a resin.

As described above, by omitting the island and extending the support lead on the back surface of the second semiconductor chip which becomes the non-overlapping portion, it is possible to allow the resin 58 to have a sufficient thickness. The external dimensions of can be made thinner.
This allows a plurality of semiconductor chips 5 to be included in one package.
It is possible to provide a semiconductor device that does not increase the thickness of the outer dimension even if 0 and 51 are stacked.

Therefore, the conventional equipment such as the mold and the test measuring device can be used as it is by only changing the lead frame, and new equipment investment is not required, so that the cost of the product can be reduced. Moreover, the thickness of the semiconductor chips 50, 51 need not be made thinner than necessary, and the mechanical strength of the silicon wafer can be maintained, so that the wafer can be handled easily after the back grinding process.

Finally, the back surface of the first semiconductor chip 50 is exposed from the encapsulating resin and may be short-circuited with the wiring of the mounting board or the like due to mounting. Therefore, this exposed portion is insulated. It is preferable to stick it on a sticker. Further, the lead frame may be bent such that the exposed portion faces upward, not downward. In this case, a short circuit with the mounting board can be prevented, but a short circuit with another element or the intrusion of static electricity or the like is considered. Therefore, it is better to attach an insulating seal.

In addition, since the island is omitted in this package, it is possible to use the conventional package size.
The resin can be sealed even on the back surface of the semiconductor chip. Therefore, measures such as short circuit with the back surface of the semiconductor chip and electrostatic breakdown can be taken with the conventional package size.

[0030]

As described above, according to the present invention,
First, the first supporting lead is brought into contact with the back surface of the second semiconductor chip corresponding to the projecting non-overlapping portion, and the two-story chip is supported by this supporting lead, whereby the second semiconductor chip Can be supported and the conventional island can be omitted. Therefore, the thickness of the island can be reduced and the thickness of the package can be reduced.

Second, by disposing the first support leads in the vicinity of each of the four parts, the two-story chip can be stably supported without twisting, and a package in which twisting is suppressed is realized. it can. Third, by arranging the U-shaped support lead close to the other side edge, it is possible to support the mechanical strength of the first support lead. Further, if the resin is placed right next to the resin injection hole of the mold, the resin flow comes into contact with the support lead, and the resin can be poured into a narrow portion which is a non-overlapping portion of the second semiconductor chip.

Fourth, by replacing the first support lead with a U-shaped lead and bringing the bottom portion into contact with the back surface of the second semiconductor chip which is the non-overlapping portion, The function of the support lead and the function of dividing the resin flow at the time of resin injection can be realized by one means.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor device for explaining an embodiment of the present invention.

FIG. 2 is a plan view of a semiconductor device for explaining another support lead.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view taken along line BB of FIG.

FIG. 5 is a plan view for explaining a conventional example.

6 is a cross-sectional view taken along the line AA of FIG.

7 is a sectional view taken along line BB of FIG.

Claims (4)

(57) [Claims] 1. A first semiconductor chip having an electrode formed on an upper surface thereof, and an electrode fixed on the first semiconductor chip and having an electrode on the upper surface.
A formed second semiconductor chip; a lead terminal extending to at least one opposing side edge pair of the first semiconductor chip; the lead terminal, the first semiconductor chip, and the lead terminal; In a semiconductor device having a connecting means for electrically connecting to the second semiconductor chip and a resin for sealing up to the periphery of the semiconductor chip, the other side pair facing the one side pair. At a position corresponding to, the second semiconductor chip projects outward from the first semiconductor chip to form a non-overlapping portion, and a back surface of the second semiconductor chip corresponding to the projected non-overlapping portion. A semiconductor device comprising a first support lead that mechanically abuts and supports the second semiconductor chip. 2. An end portion of the first support lead is
It is closer to the corner than the center of the side of the second semiconductor chip.
The half according to claim 1, wherein the halves are arranged in contact with each other.
Conductor device. 3. The second side of the second semiconductor element is positioned on the other side.
A U-shape is provided between the two first support leads to be placed.
Having a second support lead in the shape of The U-shaped bottom of the second support lead is made of resin.
Between the periphery of the second semiconductor element and the other side of the second semiconductor element
The semiconductor device according to claim 2, wherein the semiconductor device is located. 4. The first support lead has a U-shape, and a bottom portion of the U-shape is in contact with a back surface of the second semiconductor chip serving as the non-overlapping portion. The semiconductor device according to claim 1, wherein the semiconductor device is a semiconductor device.