JPH07202103A - Method for manufacturing resin-sealed semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a method for manufacturing a resin-sealed semiconductor device in which the outer lead portion of the lead is accurately bent and smoothly mass-produced. [Structure] In a surface-mounting resin-sealed type device in which a plurality of leads are drawn out from two directions, a chip is mounted, and a lead frame that has been resin-sealed is bent (3) Solder plating (4) is performed, and pre-bending processing (2) is performed as a pre-processing step for bending the lead frame. Bending punches that are used in the bending process that occurs when the leads are soldered with solder plating, and solder punching on the bending die, deterioration of the lead bending shape, and bending punches that occur due to variations in solder plating thickness. It is less likely that the clearance of the bending die will change and that the solder plating will be peeled off at the portion where the resin burr is sandwiched when the lead is bent. Further, by reducing the distance between the chips formed on the lead frame by pre-bending and restoring the distance by bending, it is possible to absorb a change in length during bending.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin-sealed semiconductor device formed by using a lead frame.

[0002]

2. Description of the Related Art In a resin-encapsulated semiconductor device, a semiconductor element (hereinafter referred to as a chip) is mounted on a lead frame, and the chip is covered with a resin encapsulant together with a part of the lead portion of the lead frame. The unnecessary portion is cut and removed, and the lead protruding from the resin sealing body is molded so as to be easily attached to the circuit board to form a product. A conventional SOP (Small Outline Package) type resin-sealed semiconductor device will be described with reference to FIG. The figure is a plan view of the SOP and a cross-sectional view of a portion along the line AA '. The packaged chip 1 is attached to a molded lead frame 2 and covered with a resin encapsulant 3 such as an epoxy resin. The lead frame 2 includes the lead 21 and the chip 1.
And a semiconductor element mounting portion 22 for mounting the. An inner lead portion of the lead 21 and a connection electrode (not shown) of the chip 1 are connected by a bonding wire 4 such as Au. Chip 1, semiconductor element mounting portion 22, inner lead portion of lead 21, and bonding wire 4
Are sealed in the resin sealing body 3. In the SOP type, the leads 21 are led out in opposite directions from two facing sides of the resin sealing body 3. The exposed portion (outer lead portion) of the lead 21 is led out in a substantially vertical direction so that it can be easily attached to a circuit board, but is bent in a substantially vertical direction in the middle, and the tip is again almost horizontal. It extends and has a so-called gull-wing shape (FIG. 8B).

Such a resin-encapsulated semiconductor device has a mounting step of mounting the chip on a lead frame, a wire bonding step of connecting the chip and the lead with a bonding wire, and a resin encapsulation for sealing the chip with a resin encapsulant. A semiconductor device assembling process is completed through a stopping process, a finishing process of processing the lead frame so as to be easily attached to the circuit board, and finally a marking process. The main finishing process is to apply solder plating on the surface of the lead frame so that it can be easily attached to the circuit board, separate unnecessary parts from the lead frame, and process the leads into gull-wing shapes so that they can be easily attached to the circuit board. It is to be.

The finishing process will be described with reference to FIG. The figure is a flow chart of this process, in which the chip is mounted, and the mounting of the mounted chip into a resin-coated lead frame is performed so as to be mounted on a circuit board. First, the lead frame is plated with solder (1). FIG. 10 is a plan view of this solder-plated lead frame. The lead frame 2 has a structure in which a frame portion A including a semiconductor element mounting portion and a lead portion is repeatedly formed in one direction, and the semiconductor element mounting portion and the lead portion of each frame portion A are the same as those of the lead frame 2. It is supported by a frame 23 on the outer periphery. The lead portion is composed of a pair of rows of leads 21 facing each other around the semiconductor element mounting portion. The lead 21 and the frame 23 are supported and connected by a support bar 24 by the frame 23. Frame part A and frame part A next to it
The columns of the leads 21 face each other via the frame 23. At this stage, the chip (semiconductor element) has already been attached to the semiconductor element mounting portion and further covered with the resin sealing body 3.

The resin encapsulation body 3 also includes a part of the lead 21 close to the chip, and the portion of the lead not covered with the resin encapsulation body 23 is called an outer lead 21. Frame parts A, A, ...
.. All the leads 21 face in the same direction. In FIG. 10, the leads are oriented in the horizontal direction of the figure. In this case, the lead part of the lead frame should be plated, but selective plating of the lead frame is
Since the number of mask processes increases, it is appropriate to plate the entire lead frame in consideration of its efficiency. The frame 23 is formed with a jig hole 6 which is also used for positioning, and is used as needed. Further, in the present invention, since electroplating is used, solder plating is performed by electrically connecting the frame of the lead frame and the plating electrode. After plating the lead frame surface, the lead frame is mounted in a predetermined position on a molding die (die) (2).

Next, the tip of the outer lead exposed from the resin sealing body of the lead portion of the lead frame and the frame portion are separated by a molding die (preliminary cutting step).
(3). FIG. 11 is a plan view of the lead frame after the preliminary cutting. As shown in the drawing, a preliminary cut is performed by cutting off the support bar 24 connecting the outer lead 21 and the frame 23. After that, the outer lead is bent (4). FIG. 12 is a plan view of the lead frame subjected to the bending process and a cross-sectional view of a portion along the line AA ′ of the plan view. The lead 21, which is horizontally led out from the resin sealing body 3, is bent in the vertical direction by a predetermined length immediately after coming out from the resin sealing body 3. Therefore, the horizontal position of the horizontal portion of the tip of the lead 21 is located slightly below the bottom surface of the resin sealing body 3. Next, after the bending process is completed, the tips of the outer leads are cut to form the lead portions to be attached to the circuit board (tip cutting step) (5). FIG. 13 is a plan view of the lead frame with the tip cut and AA ′ of this plan view.
It is sectional drawing of the part which follows a line. Most of the tips of the leads are cut off, leaving only the outer leads 21 protruding from the resin sealing body 3. The last remaining outer frame is removed to form individual resin encapsulated devices.

[0007]

Thus, in the process of assembling the resin-encapsulated semiconductor device as described above, when the forming die is bent by, for example, ironing bending, the forming die such as a bending die is formed by the conventional method. Since the plating film has already been formed when it is mounted on, the plating film formed on the surface of the lead frame adheres to the molding die and the bending punch used for bending together with the molding die. Therefore, it is difficult to accurately dispose the resin-sealed semiconductor device on the circuit board because the lead does not have a predetermined shape due to the plating attached to the molding die or the like. For this reason, conventionally, the molding die and the bending punch have been regularly cleaned to remove the attached solder plating. In addition, since the solder plating thickness varies from lot to lot or from lead frame to lead frame, the clearance between the bending punch and the molding die, which is the dimension required for bending, differs from lot to lot or from lead frame to lead frame. Also, it may cause the lead shape of the semiconductor device to be unstable. Furthermore, when resin burrs adhered on the outer leads during resin sealing, the resin burrs were sandwiched between the outer leads and solder plating even after solder plating, so the leads were bent. In this case, the solder plating at the portion where the resin burr is sandwiched may fall off.

In order to prevent the peeling of the solder plating, it is necessary to inspect a resin burr at the time of resin molding, control a resin molding die, and remove a resin burr, resulting in an increase in manufacturing process and an increase in manufacturing cost. There is. Also, it is necessary to adjust the resin molding die to minimize the occurrence of resin burr,
This leads to an increase in die cost. The present invention has been made under such circumstances, and an object of the present invention is to provide a method of manufacturing a resin-sealed semiconductor device, in which the outer lead portion of the lead is accurately bent and smoothly mass-produced. ing.

[0009]

SUMMARY OF THE INVENTION The present invention is a surface mount type resin encapsulation type device in which a plurality of leads are drawn out from two directions, and a lead frame on which a chip is mounted and resin encapsulation is bent. This is characterized in that the lead frame is plated with solder after the above. Further, it is characterized in that pre-bending processing is performed as a pre-processing step for bending the lead frame.

That is, according to the method of manufacturing a resin-sealed semiconductor device of the present invention, the semiconductor element mounting portion to which the semiconductor element covered with the resin sealing body is attached and the semiconductor element are electrically connected to each other and are opposite to each other. A lead portion composed of a plurality of leads drawn out in a direction and a frame portion formed by repeatedly supporting the frame by a frame, and bending the two portions of a boundary portion between adjacent frame portions of a lead frame substantially vertically. A lead frame pre-bending step of shortening the distance between adjacent resin encapsulants, and a step of vertically bending a predetermined region of the lead of the lead portion of the lead frame exposed from the resin encapsulant and the lead frame. A lead frame bending step of substantially returning the bent portion of the lead bent in the preliminary bending step to the original shape; A lead frame plating step of applying solder plating to the lead frame processed in the bending step, and a lead tip cutting step of separating the lead tips exposed from the resin sealing body of the plated lead frame from the frame, Between the adjacent frame parts of the repeatedly formed frame parts, the leads of the respective frame parts are opposed to each other via the frame. The shortened length of the distance between the adjacent resin encapsulants shortened in the lead frame pre-bending step corresponds to the distance between the adjacent resin encapsulants shortened by the bending in the lead frame bending step. It may be longer than the shortened length.

[0011]

[Function] A bending punch used for bending when a lead with solder plating is attached, a solder punch attached to a bending die, a lead bending shape is deteriorated, and a variation in solder plating thickness is caused. It is less likely that the clearance between the bending punch and the bending die will be changed, and that the solder plating will be peeled off at the portion where the resin burr is sandwiched when the lead bending is performed. Also, pre-bending reduces the distance between the chips formed on the lead frame,
The distance is restored by bending.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The resin-encapsulated semiconductor device of the present invention has the same configuration as the conventional SOP type resin-encapsulated semiconductor device shown in FIG. That is, the packaged chip 1 is attached to the molded lead frame 2 and covered with the resin encapsulant 3 such as epoxy resin. The lead frame 2 includes leads 21 and a semiconductor element mounting portion 22 on which the chip 1 is mounted. Inner lead portions of the leads 21 covered with resin and connection electrodes of the chip 1 (not shown)
And are connected by a bonding wire 4 such as Au. The chip 1, the semiconductor element mounting portion 22, the inner lead portion of the lead 21, and the bonding wire 4 are sealed in the resin sealing body 3. SOP type has lead 2
Reference numeral 1 denotes a surface mount type in which two sides of the resin encapsulating body 3 which face each other are led out in opposite directions. The exposed portion (outer lead portion) of the lead 21 is such that the root of the resin encapsulation body 3 is led out substantially vertically so that it can be easily attached to the circuit board. Has a so-called gull wing shape that extends almost horizontally again (see FIG. 8B).

In such an SOP type resin-sealed semiconductor device, a mounting step of mounting the chip on a lead frame, a wire bonding step of connecting the chip and the lead with a bonding wire, and a chip sealing with a resin sealing body. The resin encapsulation step, the finishing step of processing the lead frame so that the lead frame can be easily attached to the circuit board, and the marking step finally complete the semiconductor device assembling step.
The main finishing process is on the surface of the lead frame,
This is to apply solder plating for mounting on the circuit board, separate unnecessary parts from the lead frame, and process the leads into gull-wing shapes so that they can be easily mounted on the circuit board.

FIG. 1 is a flow chart showing the finishing process. 2 to 5 show a plan view and a sectional view of the lead frame processed in this step. This step is performed until the lead frame in which the mounted chip is resin-coated is molded so as to be attached to the circuit board. First, the lead frame is placed on a processing part of a molding die such as a bending die (1). Then, a lead frame pre-bending step is performed in this molding die (2). FIG. 2A is a cross-sectional view of the lead frame 2 that has been subjected to the pre-bending process.
A cross-sectional view of a portion along the line -A 'is shown in FIG. The lead frame 2 includes a semiconductor element mounting portion and a lead portion,
The frame portion A, which is supported by the frame 23, is repeatedly formed in one direction.
Considering workability, the number of frame portions of one lead frame is appropriately about 8 to 10. The semiconductor element mounting portion and the lead portion of each frame portion A are the lead frame 2
It is supported by the frame 23 between the outer peripheral portion of the frame and the frame portion A. The lead portion is composed of a pair of rows of leads 21 facing each other around the semiconductor element mounting portion. The lead 21 is supported and connected to the frame 23 via a support bar 24.

The frame portion A and the frame portion A adjacent thereto are
The rows of the leads 21 face each other with the frame 23 interposed therebetween. At this stage, the chip (semiconductor element) has already been attached to the semiconductor element mounting portion and further covered with the resin sealing body 3. The resin encapsulation body 3 also includes a part of the leads 21 close to the chip. The resin-encapsulated portion is called an inner lead, and the portion of the lead 21 exposed from the resin encapsulation body 3 is an outer part. It is called the lead. Frame parts A, A, ...
The leads 21 of all are pointing in the same direction. Figure 2
Then, the leads 21 of each frame portion A are all oriented in the horizontal direction in the figure. A jig hole 6 which is also used for positioning is formed in the frame 23 on the outer periphery of the lead frame 2,
Use as needed. Since the chip is arranged substantially in the center of the frame portion A, the resin sealing bodies 3 are arranged in the lead frame 2 at substantially equal intervals. Therefore, all the distances between the adjacent resin sealing bodies 3 are substantially constant.

The bending process performed in this step is performed to form the leads into a gull wing type as shown in FIG. 8 so that the semiconductor device is suitable for surface mounting on a circuit board. This gull-wing type is bent vertically at a part of the outer lead portion of the lead 21 protruding horizontally from the resin encapsulation body 3 a little away from the resin encapsulation body 3, and almost at a part a little away from this folding point. The outer leads 21 are bent horizontally so that the ends of the outer leads 21 are directed in a direction projecting from the resin sealing body 3. Then, in order to surface-mount this semiconductor device on a circuit board, the horizontal portion of the tip of the outer lead 21 is soldered to the wiring of the circuit board. At this time, since the bottom surface of the resin sealing body 3 does not make electrical contact with the circuit board, the semiconductor device is supported by the horizontal tip portions of the outer leads 21 extending from the two sides thereof. ing. Since the outer leads 21 of the lead frame 2 are vertically bent by a predetermined length in this manner, the distance between the adjacent resin sealing bodies 3 is shortened and the length of the lead frame 2 as a whole is also shortened. If the distance between the resin sealing bodies is shortened in this way, for example, even if the lead frame 2 is properly positioned and mounted on the molding die, the lead frame 2 is displaced from the predetermined position, and the lead frame processed here is subjected to the next step. It becomes impossible to automatically convey to the manufacturing equipment.

Therefore, in the present invention, the length of the lead frame is shortened in advance by carrying out the preliminary bending step in this way, and the bent portion is returned to the original state in the next main bending step. This prevents movement of the lead frame due to shrinkage of the lead frame caused by the bending process. In the present embodiment, the contraction of the distance between the adjacent resin sealing bodies due to the main bending process is set to, for example, about 0.32 mm. Then, bending is performed so that the shrinkage of the distance between the adjacent resin sealing bodies caused by the preliminary bending step (2) is about 0.5 mm. The length of this shrinkage needs to be longer than the shrinkage caused by the main bending process in order to achieve the intended purpose. This pre-bending process is performed at the boundary between the frame parts A, as shown in FIG. This pre-bending part B
Are pushed down, and the shrinkage between the resin sealing bodies 3 due to this is about 0.5 mm as described above. The pre-bending process of this lead frame is performed by the frame 2
Do 3 as well.

Next, a lead frame bending step is performed (3). In the lead frame pre-bending step, the pre-bending process B only needs to be performed on the boundary portion, and no particular high accuracy is required. Therefore, the positioning of the lead frame with the molding die does not have to be highly accurate. However, in this step (3), since high positional accuracy is required due to the necessity of automatic transportation, the lead frame is fixed at a predetermined position using a positioning pin (not shown) of the molding die. Then, the outer lead led out from the resin sealing body is bent into a gull wing shape. At this time, the distance between the adjacent resin encapsulants is shortened by about 0.32 mm as described above. However, since the pre-bending portion was previously made in the pre-bending step and shortened by about 0.5 mm, this The distance between the resin encapsulants, which is flattened and stretched in the portion B and which is originally shortened by the bending process, cancels each other out and does not change, and the positional accuracy is maintained. The bending process is performed on the frame part as well as the outer lead. FIG. 3 is a plan view of the lead frame after bending the lead frame and a sectional view of a portion along the line AA ′. The outer lead 21 is a gull wing molding portion C.
And the pre-bending portion B is flat.

This step will be described with reference to FIG. The outer leads 21 protruding from the resin sealing body 3 of the lead frame fixed to the processing area of the bending die 7 which is a processing die are suppressed by the stripper 8 (FIG. 6).
(A)). Next, the bending punch 9 is operated to operate the resin sealing body 3
The lead portion that is horizontally projected from and is close to the resin sealing body 3 is bent vertically (FIG. 6B). Subsequently, the gull wing molding portion C is formed by bending the tip portion of the outer lead 21 substantially horizontally (FIG. 6C). Next, after moving the lead frame, solder plating is applied to the lead frame (4). FIG. 4 is a plan view of the solder-plated lead frame and a sectional view taken along the line AA '. The lead frame 2 is plated on the entire surface other than the resin sealing body 3. Also,
Since electroplating is used in the present invention, solder plating is performed by electrically connecting the frame of the lead frame and the plating electrode.

Next, a lead tip cutting step of cutting the tips of the outer leads in the processing die is performed (5). FIG. 5 is a plan view of the lead frame with the tip cut and a cross-sectional view of a portion along the line AA ′ of this plan view. Most of the tips of the leads are cut off, leaving only the outer leads 21 protruding from the resin sealing body 3. Through this step, the outer leads 21 that are connected to the frame 23 to form one connection are separated. Finally, the remaining outer frame is removed to form individual resin-sealed semiconductor devices. The horizontal position of the horizontal portion of the tip of the outer lead 21 is located slightly below the bottom surface of the resin sealing body 3. FIG. 7 is a sectional view in which the resin-sealed semiconductor device thus formed is attached to a circuit board.
The outer lead 21 led out from the resin sealing body 3 is connected to the wiring pattern 11 of the circuit board 10 at its tip. The height H of the vertically bent portion of the outer lead 21 is equal to 1/2 of the resin sealing body 3 and the distance h from the surface of the circuit board 10 to the bottom surface of the resin sealing body 3 (H = T /
2 + h). Therefore, the shrinkage of the lead frame due to bending in the present invention is determined by the values of T and h. The lead frame of this example has a width of 16 to 63 mm and a length of 150 to 230 mm, but the present invention is not limited to such values. For example, the width of the lead frame is 10
It may be about 80 mm, and the length is 100 to 30.
It may be 0 mm. And the lead frame is, for example,
42 alloy (Ni 42 wt% Fe alloy) is used.

According to the present invention, since the outer leads of the SOP type semiconductor device are bent in the state where the tips of the outer leads are connected to the frame of the lead frame, the outer leads to which solder plating is applied even after the bending is performed Since it is electrically connected to the frame, the outer lead can be plated with solder after the lead bending process, and the outer lead surface can be bent without solder being plated. As a result, the adhesion of solder plating to the bending punch and bending die used for bending is eliminated,
It is possible to prevent the bent shape of the outer lead from being broken, and it is not necessary to regularly clean the solder plating attached to the bending punch or the bending tie. Further, since the outer lead surface is not plated with solder, the clearance between the bending punch and the bending die becomes constant, and the outer lead shape for each product becomes constant. In addition, the resin burrs attached to the outer leads during resin molding will not cause the solder plating on the part where the resin burrs generated during outer lead bending processing are sandwiched to peel off, and the resin burrs inspection and resin molding die management Also, the resin burr removal step becomes unnecessary, the manufacturing process is simplified, and the cost is reduced.
Further, it is not necessary to adjust the resin molding die in order to minimize the occurrence of resin burr.

[0022]

As described above, since the outer lead is solder-plated after the lead bending process, the outer lead surface can be bent without solder being plated.
As a result, it is possible to prevent the solder plating from sticking to the bending punch and bending die used for bending work, preventing the bent shape of the outer lead from collapsing, and regularly cleaning the solder plating on the bending punch and bending tie. There is no need to do it. Further, since the outer lead surface is not plated with solder, the clearance between the bending punch and the bending die becomes constant, and the outer lead shape for each product becomes constant. Further, since there is no shrinkage of the lead frame at the time of bending, it is possible to accurately perform automatic conveyance during the manufacturing process.

[Brief description of drawings]

FIG. 1 is a flow chart of a manufacturing process according to an embodiment of the present invention.

2A and 2B are a plan view and a cross-sectional view of a lead frame according to an embodiment of the present invention.

FIG. 3 is a plan view and a cross-sectional view of a lead frame according to an embodiment of the present invention.

FIG. 4 is a plan view and a cross-sectional view of a lead frame according to an embodiment of the present invention.

5A and 5B are a plan view and a sectional view of a lead frame according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating bending processing of an example according to the present invention.

FIG. 7 is a cross-sectional view in which the resin-sealed semiconductor device of the embodiment according to the present invention is attached to a circuit board.

FIG. 8 is a cross-sectional view of the present invention and a conventional resin-encapsulated semiconductor device.

FIG. 9 is a flowchart of manufacturing steps of a conventional resin-encapsulated semiconductor device.

FIG. 10 is a plan view and a sectional view of a conventional lead frame.

FIG. 11 is a plan view of a conventional lead frame.

FIG. 12 is a plan view and a cross-sectional view of a conventional lead frame.

FIG. 13 is a plan view and a cross-sectional view of a conventional lead frame.

[Explanation of symbols]

 1 chip 2 lead frame 3 resin encapsulant 4 bonding wire 6 jig hole, positioning hole 7 bending die 8 stripper 9 bending punch 21 lead (outer lead) 22 semiconductor element mounting part 23 lead frame frame 24 lead frame support bar

Claims (2)

[Claims] 1. A frame comprising a semiconductor element mounting portion to which a semiconductor element covered with a resin encapsulant is attached, and a lead portion electrically connected to the semiconductor element and having a plurality of leads extending in opposite directions. A lead frame in which a frame portion supported by the above is repeatedly bent, and two portions of a boundary portion between adjacent frame portions of the lead frame are bent in a substantially vertical direction to shorten a distance between the adjacent resin sealing bodies. A pre-bending step, and bending a predetermined area of a portion of the lead of the lead portion of the lead frame exposed from the resin sealing body in a vertical direction, and substantially bending the bent portion of the lead bent in the lead frame pre-bending step. The lead frame bending process to return it to its original shape, and the lead frame processed in the lead frame bending process is solder plated And a lead tip cutting step of separating the lead tips exposed from the resin encapsulant of the plated lead frame from the frame, the lead frame plating step being performed between adjacent frame sections of the repeatedly formed frame section. In the method of manufacturing a resin-sealed semiconductor device, the leads of the respective frame parts face each other with the frame interposed therebetween. 2. The shortened length of the distance between the adjacent resin encapsulants shortened in the lead frame pre-bending step is the adjacent resin encapsulation shortened by the bending in the lead frame bending step. The method for manufacturing a resin-sealed semiconductor device according to claim 1, wherein the distance between the bodies is longer than the shortened length.