JP2003133503A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which ensures the prevention of short circuitings between adjacent lead portions by suppressing cream solder from flowing out of the lead portions, while retaining the sufficient coating amount of the cream solder in conducting the actual mounting of a semiconductor chip on a substrate and not permitting bond strength between the two to lower. SOLUTION: The semiconductor device 21 is provided with a semiconductor element 22, a lead frame having a plurality of lead portions 23 which extend to the semiconductor element 22, and a resin material 24 for sealing the semiconductor element 22 and the lead portions 23. The lead portions 23 extend to the under surface of the semiconductor element 22, and electrodes 25 of the semiconductor element 22 are mounted to the ends of the extending leads 23. A groove 33 for collecting solder is formed on the under surface of each lead portion 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type semiconductor device using a lead frame.

[0002]

2. Description of the Related Art Conventionally, a chip type semiconductor device having a plurality of element electrode portions (hereinafter referred to as a semiconductor chip) has a semiconductor element mounted on a metal lead frame having a plurality of lead portions, It is formed by sealing the top with a resin material. Each of the lead portions is electrically connected to each element electrode portion of the semiconductor element, and the back surface thereof is an external electrode portion connected to a substrate such as a mother board. To mount such a semiconductor chip on the substrate, an appropriate amount of cream solder is applied to a predetermined position of the substrate to be mounted in advance, and the back surface of each lead portion of the semiconductor chip is placed thereon. Then, a reflow process is performed to bond the semiconductor chip to the substrate.

[0003]

However, when the above-mentioned semiconductor chip is mounted on a substrate via cream solder, if the lead portion which is an external electrode portion of the semiconductor chip is small or the amount of cream solder applied is too large. , Excessive cream solder overflows. In particular, in a small-sized semiconductor chip, the lead portion itself is minimized, and the space between adjacent lead portions is very narrow in order to increase the arrangement density. Further, since the back surface of the lead portion and the board to be mounted are both flat surfaces, it is easy to spread the semi-liquefied cream solder to the surroundings by sandwiching it between the back surface of the lead portion and the board. Therefore, the cream solder heated and melted by the reflow process may spread and protrude, and adjacent lead portions may be short-circuited by the cream solder. In the past, measures such as suppressing solder squeeze out by reducing the amount of cream solder applied were taken, but conversely, if the amount of cream solder applied is too small, the bonding strength between the semiconductor chip and the substrate is increased. There was a problem that became weak.

Therefore, an object of the present invention is to secure a sufficient amount of cream solder to be applied when mounting it on a board without lowering the bonding strength with the board, and to apply the applied cream solder to the lead portion. It is an object of the present invention to provide a semiconductor device in which the protrusion of the lead portions is suppressed and a short circuit between adjacent lead portions is reliably prevented.

[0005]

In order to solve the above-mentioned problems, a semiconductor device according to claim 1 of the present invention includes a semiconductor element and a lead frame having a plurality of lead portions extending toward the semiconductor element. In a semiconductor device including the semiconductor element and a resin material that seals the lead section, the lead section extends to a lower surface side of the semiconductor element, and an element electrode section of the semiconductor element is mounted on the extended tip section. A solder pool is formed on the back surface of the lead portion.

According to the present invention, when the semiconductor chip is bonded onto the substrate such as the mother board via the cream solder, a part of the fluidized cream solder may escape into the solder pool formed on the back surface of the lead portion. Therefore, the solder paste can be effectively prevented from protruding from the lead portion.

The solder pool is preferably formed by a recess provided on the back surface of the lead portion. The recess can be easily formed by etching or the like when molding the lead frame. As a concrete example of the recessed portion, for example, a recessed groove or a recess provided on the back surface of the lead portion, or the entire back surface of the lead portion is roughened by an etching process to make it a rough surface. The depth, number, position, shape, etc. of the recessed grooves or recesses can be set as appropriate, but the effect is great when they are formed on both ends of the back surface of the lead portion where cream solder easily escapes.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a semiconductor device according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing a semiconductor chip according to the first embodiment,
2 is a sectional view showing a state before the semiconductor chip is mounted on a substrate, and FIG. 3 is a sectional view showing a state after the semiconductor chip is mounted on the substrate.

As shown in FIGS. 1 and 2, a semiconductor chip 21 according to this embodiment includes a semiconductor element 22, four lead portions 23 on which the semiconductor element 22 is mounted, and the lead portion 23. It is composed of a resin material 24 that seals the semiconductor element 22. The semiconductor element 22 is a square thin plate of silicon crystal, and has element electrode portions 25 at four corners.

The lead portion 23 is formed on a strip-shaped lead frame 31 as shown in FIG. 4 by etching or the like, and the tips thereof face the frame body 32 in the mounting direction of the semiconductor element 22. Is extended.
The tip of the lead portion 23 extends to the lower side of the element electrode portions 25 formed at the four corners of the semiconductor element 22, and a concave surface 28 on which the end portion of the semiconductor element 22 is placed is formed on the upper surface of the tip. ing. In addition, the back surface 29 of each lead portion 23
A concave groove 33 having a rectangular cross section is formed at each of the front end and the rear end of the. As shown in FIGS. 2 and 3, these recessed grooves 33 are formed when the lead portion 23 is bonded to the substrate 12.
A part of the cream solder 13 sandwiched between the two serves as a solder pool that escapes. By forming the groove 33 at the front end and the rear end of the back surface 29, it is possible to effectively prevent the cream solder 13 from protruding from the front and rear ends of the lead portion 23.

In the semiconductor element 22, the lead portion 23 is formed by the solder bumps 26 formed on the element electrode portion 25.
At the same time when it is joined to the recessed surface 28, electrical conduction is achieved. Further, by sealing the upper surfaces of the semiconductor element 22 and the lead portion 23 with the resin material 24, the semiconductor chip 2
1 is formed, but the resin material 24 does not have the groove 33 when the resin is sealed.
It is desirable to mask so that it does not flow inside.

2 and 3 show the case where the semiconductor chip 21 having the above-mentioned structure is mounted on the substrate 12. First, the cream solder 13 is applied to the electrode surface of the substrate 12. The cream solder 13 has a semi-solid shape having fluidity in the applied state, and is liquefied by applying heat treatment such as reflow. It adheres to both sides and solidifies in that state. Next, cream solder 1
So that the lead portion 23 is located on the semiconductor chip 2
1 is placed and passed through a reflow oven to make cream solder 1
3 is melted and solidified to bond the semiconductor chip 21 to the substrate 12. Since the cream solder 13 is melted and liquefied inside the reflow furnace, the cream solder 13 spreads over the back surface 29 of the lead portion 23, but the concave grooves 33 are formed at the front and rear ends of the back surface 29. Therefore, the cream solder 13 that tries to spread outward escapes into the concave groove 33 and does not protrude from the back surface 29 of the lead portion 23.
3 solidifies. The amount of the cream solder 13 applied is appropriately adjusted according to the size of the back surface 29 of the lead portion 23, but since the concave groove 33 is formed, it is possible to suppress the protrusion from the back surface 29 even if a slightly larger amount is applied. You can As described above, the amount of cream solder 13 applied is not too small as in the conventional case, so that the bonding strength of the semiconductor chip 21 can be sufficiently secured.

FIG. 5 shows a second embodiment of the semiconductor chip according to the present invention. In the semiconductor chip 41 according to this embodiment, a pair of front and rear recesses 44 are formed on the back surface 46 of the lead portion 43, and the recesses 44 are used as solder reservoirs. Since the recess 44 forms a closed space unlike the recessed groove 33, the cream solder 13 that has escaped into the recess 44 can be confined, and the protrusion from the lead portion 43 can be suppressed more effectively. be able to. Also,
A step such as masking is not required even when the resin is sealed.

FIG. 6 shows a third embodiment of the semiconductor chip according to the present invention. In the semiconductor chip 51 according to this embodiment, the back surface 56 of the lead portion 53 is roughened by etching or the like, and the entire back surface 56 has a rough surface 5 having an uneven shape.
4 is formed. By using the concave portion of the rough surface 54 as a solder pool, the cream solder 1 applied on the substrate 12
3 can escape into the recessed portion of the rough surface 54 formed on the entire back surface 56, so that the cream solder 13 can be effectively prevented from protruding and the semiconductor chip 51 can be prevented.
The joint strength between the substrate 12 and the substrate 12 can be increased at the same time.

As described above, the semiconductor chip 2 of the present invention
1, 41 and 51 have solder pools composed of recessed grooves 33, recesses 44 and roughened surfaces 54 on the back surfaces 29, 46 and 56 of the lead portions 23, 43 and 53, which are joint surfaces with the substrate 12. Since the cream solder 13 is provided, excess cream solder 13 is allowed to escape into these solder pools, so that the liquefied cream solder 13 is effectively prevented from protruding. Also, cream solder 13
Since a sufficient coating amount can be secured, the bonding strength between the semiconductor chips 21, 41, 51 and the substrate 12 is not reduced.

The semiconductor chips 21, 41, 51 of each of the above-described embodiments have been described for the case where the device electrode portion 25 of the semiconductor device 22 has four poles.
It is not limited to only poles. In addition, the lead portion 2
The number of 3, 43, 53 can also change depending on the number of poles of the semiconductor element to be mounted. Further, in each of the above-described embodiments, flip chip mounting using the solder bumps 26 is shown as the mounting form of the semiconductor element 22, but it goes without saying that the present invention can also be applied to a semiconductor chip using a bonding wire.

[0017]

As described above, according to the semiconductor device of the present invention, when the semiconductor device is bonded to the substrate such as the mother board via the cream solder, the solder pool is formed on the back surface of the lead portion. By letting a part of the cream solder escape, it is possible to effectively prevent the cream solder from protruding from the lead portion.

Further, since the amount of cream solder applied is not too small as in the conventional case, the bonding strength of the semiconductor device can be sufficiently secured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a state before the semiconductor device of FIG. 1 is mounted on a substrate.

3 is a cross-sectional view showing a state after the semiconductor device of FIG. 1 is mounted on a substrate.

4 is a perspective view of a lead frame which is a base of the semiconductor device of FIG.

FIG. 5 is a perspective view showing a second embodiment of the semiconductor device according to the present invention.

FIG. 6 is a sectional view showing a third embodiment of the semiconductor device according to the present invention.

[Explanation of symbols]

21, 41, 51 Semiconductor device (semiconductor chip) 22 Semiconductor element 23,43,53 Lead part 24 Resin material 29,46,56 back side 31 lead frame 33 groove 44 recess 54 rough surface

Claims (2)

[Claims] 1. A semiconductor device comprising a semiconductor element, a lead frame having a plurality of lead portions extending toward the semiconductor element, and a resin material for sealing the semiconductor element and the lead portion, wherein the lead portion is Extending to the lower surface side of the semiconductor element, the element electrode portion of the semiconductor element is mounted on the extended tip portion,
A semiconductor device, wherein a solder pool is formed on the back surface of the lead portion. 2. The semiconductor device according to claim 1, wherein the solder pool is formed by a recessed portion provided on the back surface of the lead portion.