JPH041504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the field of semiconductor technology, and particularly to a method of assembling a semiconductor device in that field.

[Conventional technology]

Conventionally, a semiconductor device having a structure in which a plurality of leads (external terminals) protrude from the side surface of a sealed body is attached to a mounting board (wiring board) such as a printed circuit board or a ceramic board, as shown in FIG. 3a or 3b. The structure shown is known. In the structure shown in FIG. 3a, the leads 2 extending from the sealing part 1 are bent in the same direction midway to form an in-line shape, each lead 2 is pushed into a mounting hole 4 provided in a mounting board 3, and the wiring board 3 is
It has a structure (insertion type) in which the distal end portion that penetrates through the mounting board 3 is fixed to the mounting board 3 via the solder 5. The structure shown in FIG. 3b is a structure in which the tip of the inline lead 2 is bent outward again to make it a flat type, and the flat tip 6 is placed on the mounting board 3 and fixed via solder (not shown). .

Note that the wiring layer on the surface of the mounting board is omitted in these figures.

[Problem to be solved by the invention]

The former insertion type structure requires drilling a mounting hole in the mounting board, which has the disadvantage of increasing the cost of the mounting board. On the other hand, the latter flat type can reduce the cost of the mounting board compared to the insertion type, but has the disadvantage that the mounting area is large because the leads are protruded laterally, and the packaging density is low.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for assembling a semiconductor device that can reduce the cost of a mounting board and also improve the packaging density.

[Means to solve the problem]

To achieve the above object, the present invention includes a quadrilateral lead frame for partitioning the components of one semiconductor device, and a semiconductor circuit element positioned at the center of the partitioned lead frame. a quadrilateral tab with a main surface to be fixed, and for each side of the tab, one side has a free end face close to each side of the tab, and the other side has a free end face facing each side of the lead frame. A plurality of leads having end faces arranged at a predetermined interval from each other, a dam connecting the plurality of leads, a tab lead extending from the tab collar and connecting to the dam, and connecting the dam and the lead frame. a step of preparing a lead frame composed of a connecting portion, and coating the lead frame with a film having good solder wettability to improve the solder wettability of the plurality of leads including the other free end surface. fixing a semiconductor circuit element having a plurality of electrodes on its main surface to the main surface of the tab; and connecting one free end of the lead and the electrode of the semiconductor circuit element with a wire. a step of resin-sealing the semiconductor circuit element, inner ends of leads, and wires in a portion partitioned by the dam to form a quadrilateral resin-sealed portion; and cutting the dam and the tab lead. Then, the resin-sealed part is cut off from the frame, and the leads including the other free end faces leading out in four directions from the sides of the sealing body are bent from predetermined points to remove the resin-sealed part. A method for assembling a semiconductor device, comprising the steps of: obtaining a semiconductor device in which a plurality of leads are arranged so that their free end faces can come into contact with the mounting board surface by slightly protruding from the bottom surface. It is in.

[Effect]

According to the above-mentioned means, since the free end surfaces of the plurality of leads are coated with a film having good solder wettability, the solder wettability of the lead free end surfaces is improved, and the lead outer end surfaces are brought into contact with the mounting board surface. This enables reliable soldering and mounting.

Therefore, according to the method for assembling a semiconductor device obtained by the present invention, there is no need to provide a mounting hole in the mounting board, so that the manufacturing cost of the mounting board can be reduced.

Also, like the conventional flat type, the lead 2
Since there is no need to protrude, the mounting area can be reduced and the mounting density can be improved.

〔Example〕

The structure of the present invention will be explained below with reference to Examples.

FIG. 1 shows a mounting structure of a semiconductor device obtained by the assembly method of the present invention.

The semiconductor device 7 shown in the figure is made up of a resin-sealed part 8 having a rectangular parallelepiped shape and a plurality of leads 9 extending from the side surface of the resin-sealed part 8 and bent downward in the middle. Then, this semiconductor device 7 is mounted by bringing the tip end surface of the lead 9 extending downward into contact with the upper surface of the mounting board (wiring layer is omitted) 10, and by using solder 11, which is a solder material, in the contact portion. It is fixed to the substrate 10.

In this mounting structure, the solderability (solder wettability) of the lead end face greatly influences the quality of the connection. Therefore, in order to improve solderability, it is necessary to apply silver plating to the tip end surface of the lead.

A method for assembling a semiconductor device according to the present invention that satisfies this requirement will be described below.

According to the present invention, a semiconductor device is assembled using the lead frame 12 shown in FIG. In this lead frame 12, the outer end surface of the lead 9 (the lead end surface introduced from the mold section) is separated from the lead frame 13 at the stage of manufacturing the lead frame. This lead frame is entirely silver plated. As a result, the outer end surfaces of the leads 9 are also coated with silver plating. Then, after fixing the semiconductor circuit element 15 on the tab 14, the electrode of the semiconductor circuit element 15 and the free end of the lead 9 close to the tab 14 are connected with a wire 16, and then the portion surrounded by the dam 17 is connected. It is molded with resin, and the unnecessary dam 17 and lead frame 13 are cut and removed. Further, the tab lead 18 is cut from the resin sealing part (mold part) 19 or the base of the lead frame 13. By bending the leads leading out from the sides of the resin-sealed part in four directions from predetermined points, the lead end faces are made to slightly protrude from the lower surface of the resin-sealed part as shown in FIG. Obtain a semiconductor device.

Note that with a lead frame shaped as shown in Figure 2, there is a risk that the dam may bend outward due to the internal pressure of the resin during resin molding, so connect unnecessary empty lead ends to the lead frame. It is recommended that reinforcement pieces be placed between the dam and the lead frame. Since these empty leads and reinforcing pieces are removed from the leads by cutting the dam, there is no particular problem in manufacturing.

[Effects of the Invention] As described above, according to the method for assembling a semiconductor device of the present invention, even the end faces of the leads are sufficiently coated with a film with good solder wettability, and the solder wettability of the outer end faces of the leads is improved. This improves the soldering performance and enables reliable soldering mounting with the lead end surface in contact with the mounting board. Therefore, the reliability of soldering can be sufficiently ensured, and the reliability of mounting the semiconductor device can be improved.

Therefore, the semiconductor device obtained by the assembly method of the present invention can reduce the mounting board cost,
It is possible to improve the packaging density. Further, there is an effect that the mounting cost of the semiconductor device can be reduced.

Further, according to the present invention, the mounting area can be further reduced by making the distance l from the outer edge of the resin sealing part 8 to the bent part of the lead as short as possible.

Furthermore, if the leads are bent at the interface of the resin-sealed portion, there is an advantage that the leads can be easily bent. Further, by shortening the length (height H) of the leads, the leads are less likely to get caught when handling the semiconductor device. Therefore, the occurrence of lead bending can also be reduced.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing a mounting structure for a semiconductor device according to an embodiment of the present invention. FIG. 2 is a plan view of a lead frame used in one embodiment of the present invention. FIG. 3a is a sectional view showing one form of a conventional mounting structure for a semiconductor device. FIG. 3b is a front view showing another form of the conventional mounting structure for a semiconductor device. 1... Sealing part, 2... Lead, 3... Mounting board, 4...
Mounting hole, 5...Solder, 6...Flat end portion, 7...Semiconductor device, 8...Resin sealing part, 9...Lead, 10...Mounting board, 11...Solder, 12...Lead frame, 13
...Lead frame, 14...Tab, 15...Semiconductor circuit element, 16...Wire, 17...Dam, 18...Tab lead, 19...Mold part.

Claims (1)

[Claims] 1. A quadrilateral lead frame for partitioning the components of one semiconductor device, and a main surface to which a semiconductor circuit element is to be fixed, which is located in the center of the partitioned lead frame. and a quadrilateral tab having, for each side of said tab, one side having a free end face proximate to each side of said tab, and the other side having a free end face facing each side of said lead frame. A plurality of leads arranged at predetermined intervals, a dam connecting the plurality of leads, a tab lead extending from the tab and connecting to the dam, and a connecting portion connecting the dam and the frame body. and a step of coating the lead frame with a film having good solder wettability to coat a plurality of leads including the other free end surface with a film having good solder wettability. fixing a semiconductor circuit element having a plurality of electrodes on its main surface to the main surface of the tab; connecting one free end of the lead to an electrode of the semiconductor circuit element with a wire; sealing the semiconductor circuit element, one free end of the lead, and the wire in a portion partitioned by the dam with a resin to form a quadrilateral resin sealing portion; cutting the dam and the tab lead; , the resin sealing part is cut off from the lead frame, and the leads including the other free end surface led out in four directions from the sides of the sealing part are bent from a predetermined point from the bottom surface of the sealing part. A method for assembling a semiconductor device, comprising the steps of: obtaining a semiconductor device in which a plurality of leads are arranged so that their free end faces can come into contact with a mounting board surface by slightly protruding them;