JPH06204379A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent whisker-shaped solder plating from being generated even if PPF is used for a lead frame. CONSTITUTION:The clamping pressure for clamping a mold by holding a solder plating 29 of PPF 21 from both sides should be a pressure preventing the part of the solder plating 29 which is held by the mold from being deformed. Then, when injection of a mold resin 8 into the mold is completed, the clamping pressure is increased and final forming pressure is applied to the mold resin 8. Therefore, since the mold resin 8 has been filled into the part inside a dambar even if the clamping force for deforming the solder plating 29 is reached, deformation of the solder plating 29 due to the presence of the filled mold resin 8 and hence squeeze-out into the damper can be prevented. Also, by controlling the rising timing of the clamping force of the mold based on the amount of displacement of a plunger, the squeeze-out into the inside of the dambar of the solder plating can be positively prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a resin-sealed semiconductor device using a lead frame, and in particular, a lead frame having an outer lead portion plated with solder (alloy of Sn and Pb) in advance is used. The present invention relates to a method of manufacturing a resin-sealed semiconductor device.

[0002]

2. Description of the Related Art As a resin-sealed semiconductor device using a lead frame, a structure shown in FIG. 6 is known. This semiconductor device includes a lead frame 1, a semiconductor element 6 mounted on the lead frame 1, and a molding resin 8 that exposes a part of the lead frame 1 to the outside and covers the semiconductor element 6 and the lead frame 1. Prepare The lead frame 1 has a die pad 2 for mounting the semiconductor element 6 and a plurality of lead terminals 3 on both sides with the die pad 2 interposed therebetween. The portion of each lead terminal 3 covered with the molding resin 8 is the inner lead portion 4.
The portion exposed to the outside of the mold resin 8 is referred to as the outer lead portion 5.

Silver plating 2a is formed on the upper surface and side surfaces of the die pad 2, and a semiconductor element 6 is mounted on the silver plating 2a. A silver plating 4a is formed on the end of the inner lead portion 4 on the die pad 2 side, and the silver plating 4a and the semiconductor element 6 are connected by a wire 7. An outer plating 9 made of solder or tin is formed on the outer lead portion 5.

A semiconductor device having such a structure is initially manufactured by a manufacturing process using a mold as shown in FIG. That is, in this manufacturing process, the die pad 2
The lead frame 1 having the silver plating 2a on the inner lead portion 4 and the silver plating 4a on the inner lead portion 4 is used. First, the semiconductor element 6 diced to the lead frame 1 is diced.
Is die-bonded onto the inner lead portion 4 to form a semiconductor element 6
And the lead frame 1 are wire-bonded.

Next, the lead frame 1 is set in a mold. Then, the mold resin 8 is sealed in the mold,
Then, it is held (cured) for a predetermined period of time. After that, the outer lead portion 5 is subjected to exterior plating 9, the lead terminal 3 is formed and bent to form a final product, and thereafter, a test is performed to manufacture.

However, in this conventional manufacturing process, the outer plating 9 of the outer lead portion 5 formed after the molding resin 8 is sealed is performed in a surface treatment step different from the step using the mold, and the treatment is performed. Since the place where the process is performed is different, there is a drawback that the whole manufacturing process requires a considerably long time.

Therefore, in order to eliminate the surface treatment process for forming the exterior plating from the manufacturing process of the semiconductor device and shorten the time, silver plating is applied to the inner lead portion and the die pad and solder plating is applied to the outer lead portion in advance. Lead frame (hereinafter referred to as PPF (Pre-Plated-F
name). ) Is used to manufacture a resin-sealed semiconductor device.

FIG. 8 is a cross-sectional view showing a part of the resin-sealed semiconductor device using the PPF, showing a state in which the PPF 21 is sandwiched between the molds 10 during manufacturing. As shown in this figure, in the resin-sealed semiconductor device using the PPF 21, the silver plating 24a formed on the inner lead portion 24 and the solder plating 29 formed on the outer lead portion 25 do not come into contact with each other, Also, in consideration of the corrosion resistance of the outer lead portion 25, a structure is often adopted in which a part of the solder plating 29 enters the mold resin sealing region, that is, the cavity portion 13 of the mold 10, and the solder plating 29 is located above and below the mold. 11,
It is sealed in the mold resin while being clamped to the 12 parting surfaces 11a and 12a.

The manufacturing process in this case is performed as shown in FIG. First, the inner lead portion 24 and the die pad are preliminarily silver-plated 24a and the outer lead portion 25 is solder-plated 29 to the PPF 21, and the dicing semiconductor element is die-bonded on the die pad to wire the semiconductor element and the PPF 21 to each other. Bond. The PPF 21 is set in a mold.

Next, the die 10 is clamped at a pressure of about 3 ton / cm ^{2 with} respect to the area of the PPF 21 portion sandwiched by the die. Next, the mold resin melted in the pot formed in the mold 10 is extruded by the plunger provided in the injection molding machine, and the mold resin is injected into the cavity 13 of the mold 10 through the runner of the mold 10. After pouring, when the filling is completed, a final molding pressure of about 100 kg / cm ² is applied to hold and cure for about 2 minutes. Then, it is removed from the mold 10 and a predetermined test is performed.

[0011]

By the way, in the case of the conventional manufacturing process shown in FIG. 9, the PPF 2 in which the solder plating 29 is formed on the outer lead portion 25 as described above.
Since 1 is often used, die bonding, wire bonding, or the like in a temperature range where the solder does not melt, for example, 175 ° C. or lower,
It is necessary to inject mold resin. Further, in the mold resin injection step, as shown in FIG. 10, the vicinity of the dam bar 23a provided for connecting the lead terminal 23 to the outer lead portion 25 is about 3 by the parting surface of the mold.
The mold is clamped at a pressure of ton / cm ² .

To this end, as shown in FIGS. 8 and 10, the solder plating 2 clamped at the parting surface of the mold is used.
The nine portions may be deformed, and the deformed solder-plated portion 29a that protrudes between the lead terminals 23 may be formed. When the mold resin is injected into the cavity 13 of the mold, as shown in FIG. 11 (a sectional view taken along the line AA 'in FIG. 10), the portion surrounded by the dam bar and the lead terminal 23. (Hereafter, this part is called the part inside the dam bar.)
Is filled with the mold resin 8.

Further, before cutting the dam bar 23a and bending each lead terminal 23 to finally finish the manufacturing process, the mold resin 8 filled in the inner part of the dam bar is dropped. Since 29a exists in a state of protruding between the lead terminals 23, the molding resin 8 cannot be dropped sufficiently. In addition, when the dam bar 23a is cut in this state, the deformed solder plated portion 29a remains attached to the side surface of the lead terminal 23, and the lead terminal 23
12 is bent, the solder-plated portion remaining at the time of cutting becomes a beard shape that is bent away from the side surface of the lead terminal 23, and as a result, this beard-shaped solder is formed. The plating 29b not only electrically shorts the lead terminals 23, but also the beard-shaped solder plating 29
The loss of b causes various problems.

As a countermeasure against this problem, there has been proposed a method of manufacturing without forming the solder plating 29 on the PPF portion to be clamped by the mold. However, in this case, the lead terminal portion where the solder plating is not formed is not sealed with the mold resin and is exposed to the outside, so that the corrosion resistance is inferior and a resin burr is generated in the exposed portion. This is not preferable because it causes another problem.

The present invention has been made to solve the above-mentioned problems of the prior art, and a PPF is attached to a lead frame.
It is an object of the present invention to provide a method for manufacturing a semiconductor device, which can prevent the occurrence of beard-like solder plating even if the above method is used.

[0016]

According to a method of manufacturing a semiconductor device of the present invention, a lead frame is connected to a semiconductor element, a part of the lead frame is exposed to the outside, and the semiconductor element and the lead frame are made of resin. Covered semiconductor device,
In the method of manufacturing a semiconductor device manufactured by using a mold, as the lead frame, an outer lead portion exposed to the outside of the resin is subjected to solder plating, and the lead frame is set in the mold, A step of sandwiching the solder-plated outer lead portion from both sides and clamping the mold with a first pressure applied, and a step of injecting a mold resin into the cavity portion of the mold in the clamped state. And, after the injection of the mold resin into the cavity is completed, the mold clamping pressure of the mold is set to a second pressure higher than the first pressure.
And a step of applying a final molding pressure to the molding resin injected into the cavity after increasing the mold clamping pressure of the mold to a second pressure.
Thereby, the above object is achieved.

The timing of raising the mold clamping pressure from the first pressure to the second pressure is such that the plunger is used as a means for injecting the mold resin into the cavity of the mold, and the displacement amount of the plunger is set. It is preferable to carry out based on.

As the lead frame, one having solder plating formed from the outer lead portion to the portion covered with the molding resin can be used.

[0019]

According to the present invention, the mold clamping pressure when clamping the mold by sandwiching the outer lead part plated with the solder of PPF from both sides does not deform the solder plated part sandwiched by the mold. Use as pressure. Next, the mold resin is injected into the cavity of the mold in this state, and when the injection is completed, the mold clamping pressure of the mold is increased and the final molding pressure is applied to the mold resin.

Therefore, even when the mold resin injection is completed and the mold clamping pressure is such that the solder plating is deformed, at that time, the mold resin is filled between the lead terminals, that is, inside the damper. Therefore, the presence of the filled mold resin prevents the solder plating from being deformed and protruding to the inside of the dam bar. As a result, beard-like solder plating does not occur.

Further, when a plunger is used as the means for injecting the mold resin, if the timing for increasing the mold clamping pressure of the mold is controlled based on the displacement amount of the plunger, the solder plating is deformed and the inside of the dam bar is deformed. It can be more reliably prevented from protruding to the part.

[0022]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a sectional view showing a semiconductor device manufactured by applying the present invention. This semiconductor device includes a lead frame 21, a semiconductor element 6 mounted on the lead frame 21, and a molding resin 8 that exposes a part of the lead frame 21 to the outside and covers the semiconductor element 6 and the lead frame 21. Prepare The lead frame 21 has a die pad 22 for mounting the semiconductor element 6 and a plurality of lead terminals 23 on both sides with the die pad 22 interposed therebetween. The portion of each lead terminal 23 covered with the molding resin 8 is referred to as an inner lead portion 24,
The exposed portion of the molding resin 8 is called the outer lead portion 25.

Silver plating 22a is formed on the upper surface and side surfaces of the die pad 22, and the semiconductor element 6 is mounted on the silver plating 22a. A silver plating 24a is formed on the end of the inner lead portion 24 on the die pad 22 side, and the silver plating 24a and the semiconductor element 6 are connected by a wire 7. The outer lead portion 25 and the inner lead portion 24 connected to the outer lead portion 25 are provided with silver plating 24
Solder plating 29 is formed separately from a.

Next, an injection molding machine used for manufacturing the semiconductor device of this embodiment will be described.

FIG. 3 is a front view showing the entire injection molding machine 30, and FIG. 4 is a perspective view thereof. Injection molding machine 30
Is the lower die 12 fixed on the base 31 and the base 31
Movable platen 3 that moves up and down along a guide 31a standing upright
2 and an upper die 11 fixed to the movable plate 32 and configured to move up and down with respect to the lower die 12. A runner 12b, a gate 12c, and a cavity portion 12d are formed on the upper layer portion of the lower mold 12. A runner, a gate, and a cavity, which are not shown, are formed in a lower layer portion of the upper die 11 on one side, and a pot 11b for accommodating the mold resin is formed so as to penetrate therethrough. In addition, runners provided in the lower mold 12 and the upper mold 11, respectively,
The gate and the cavity have the same shape and the like in the lower mold and the upper mold. Cavity part 12 of lower mold 12
The d and the cavity of the upper mold 11 form the cavity 13 shown in FIG.

Above the pot 11b is provided a plunger 34 which is vertically moved by, for example, a rod 33a of a hydraulic cylinder 33, and the lower end portion of the plunger 34 enters the pot 11b. When the lower end of the plunger 34 enters the pot 11b, the pot 11
The mold resin 8 warmed in b is pushed out from the pot 11b arranged as shown in FIG.
It is injected into the cavity portion 12d and the like through the runners 12b and the like of Nos. 1 and 12 and the gate 12c and the like. This cavity part 1
2d or the like, that is, 13 described above, is set with the PPF 21 on which the semiconductor element 6 described above is mounted.

A displacement amount measuring instrument 35 for measuring the displacement amount of the plunger 34 is provided near the plunger 34. This displacement amount measuring device 35 is, for example, the plunger 3
4 and a light receiver 35b such as a one-dimensional CCD that is fixed to the vicinity of the plunger 34 by a support (not shown) and receives the light emitted from the light emitter 35a.
With. The displacement amount of the plunger 34 by the displacement amount measuring device 35 is based on the standby position before the plunger 34 pushes out the molding resin, and a predetermined portion of a plurality of light receiving portions provided in the light receiving device 35b receives light from the light emitting device 35a. It is measured by That is, the displacement amount measuring device 35 in this example detects the displacement amount only when the plunger 34 moves from the reference position by a certain distance. The amount of displacement can be changed by adjusting the positions of the light emitter 35a and the light receiver 35b.

The signal measured by the displacement measuring instrument 35 is given to the mold clamping / mold opening control circuit 36. The mold clamping / mold opening control circuit 36 drives a hydraulic drive device 37 that performs the mold clamping / mold opening of the mold 10 based on the input signal. The height position and the pressing force with respect to the die 12 are adjusted. In addition, in FIG. 4, although the plunger 34 adopts a single plunger system, the plunger 34
It is also possible to use a multi-plunger system having a plurality of pots 11b.

Next, a method of manufacturing the semiconductor device of the present invention will be described.

First, the temperature of the mold 10 is set to 160 ° C. so that the solder plating 29 of the PPF 21 does not melt.
When such preparation is completed, the PPF 21 in which the inner lead portion 24 and the die pad 22 are preliminarily formed with silver plating 24a and 22a with a thickness of 5 μm and the outer lead portion 25 including the dam bar portion is formed with a solder plating 29 with a thickness of 6 μm in advance, Dicing the semiconductor element 6 to 160-1
Die bond on the die pad 22 using an epoxy-based silver paste that can be cured at 70 ° C. After that, the wire 7 is wire-bonded between the semiconductor element 6 and the silver plating 24a of the inner lead portion 24 while applying ultrasonic waves at 160 to 170 ° C. It should be noted that the PPF 21 in the state where the die bonding and the wire bonding are performed in this way
May be prepared in advance and used.

Next, the die-bonded or wire-bonded PPF 21 is set in the mold 10.

The subsequent mold resin injection step will be described with reference to FIG. In FIG. 1, the horizontal axis represents the forming time, and the vertical axis represents the plunger displacement amount (solid line), the lead frame mold clamping pressure by the mold (dashed line) and the molding pressure (broken line). Shows.

The mold 10 on which the PPF 21 is set is clamped. The mold clamping pressure at this time point t ₀ is about 1 ton with respect to the area of the PPF 21 portion sandwiched by the molds 10.
/ Cm ² of pressure.

Next, the mold resin 8 preheated with a high frequency is put into the pot 11b, and the mold resin 8 melted in the pot 11b is t ₀ by the plunger 34.
Push out for a period of ~ t ₁ . Until the time t ₁ when the filling of the mold resin 8 into the cavity portion 13 is completed, almost no molding pressure is applied to the flowing mold resin 8. Therefore, until the time t ₁ , even if the mold clamping pressure is ₁ ton / cm ² , PP
There is no resin burr on the lead terminal 23 of F21.

After the time point t ₁ , the molding pressure starts to be applied. However, when the actual application of the molding pressure is started, the actual cavity portion 13 has a certain distance from the pot 11b, and due to the increase in the density of the filled resin, the actual cavity portion 13 may slightly increase from the time point t _1. The time point t _{2 has} elapsed, and a small time lag (t ₂ −t ₁ ) occurs during this time. On the other hand, the lead frame clamping pressure by the mold is set to, for example, the molding resin 8 immediately before the molding pressure is applied.
Increase in time t ₁ the injection has been completed in a predetermined 3 ton / cm ^2. The mold clamping pressure of 3 ton / cm ² is the same as the mold 1
It is a value for the area of the PPF21 portion sandwiched by 0s. The timing for raising the mold clamping pressure is that the mold clamping / mold opening control circuit 36 drives the hydraulic drive device 37 when the displacement amount of the plunger 34 measured by the displacement amount measuring device 35 reaches a predetermined value. Done by. As the predetermined value, a value when the plunger 34 reaches the lowest point or a position slightly above the lowest point is used.

At time t ₂ , the molding pressure is set to 1
The final molding pressure is set to 00 kg / cm ² , the pressure is applied to the mold resin 8, and this state is held for about 1.5 to 2 minutes to cure. After that, at time t ₃ , the mold clamping / mold opening control circuit 36 drives the hydraulic drive device 37 to raise the upper mold 11 to open the mold, and subsequently, the mold 10 is sealed with the resin as the product. The stopped semiconductor device is taken out.

After that, the product is post-cured at 160 ° C., undergoes a marking step, is cut and bent for lead terminals, is subjected to an electrical test and a visual inspection, and is shipped.

In the above embodiment, the light emitter 35a is provided on the surface of the plunger 34, and the light receiver 35a is provided in the vicinity of the plunger 34.
Although b is fixed, a light receiver 35b may be provided on the surface of the plunger 34 and the light emitter 35a may be fixed near the plunger 34.

In the above embodiment, the light emitting device 35a and the light receiving device 35 are used.
However, the present invention is not limited to this, and the plunger 34 and its vicinity are designed with a non-magnetic material such as austenitic stainless steel, and the plunger 34 is It is also possible to attach a small detection target made of a ferromagnetic material and use a magnetic sensor to detect the detection target. However, if a displacement amount measuring device is attached to the injection molding machine, the displacement amount measuring device may be used.

In the above embodiment, the present invention is applied to the pot type transfer molding performed by using the compression molding machine, but the present invention is not limited to this and can be similarly applied to general plunger molding. The extruder can also be applied when a plunger extruder or a ram extruder is used.

[0042]

As described above, in the case of the present invention, when the mold is clamped, the portion of the PPF where the solder plating is formed is sandwiched, but the clamping pressure is set to a low pressure that does not deform the solder plating, A pressure to deform the solder plating sandwiched between the molds because the mold resin is injected and filled in the mold in that pressure state, and the mold clamping pressure is raised immediately before the final molding pressure is applied. When is added, the inside of the dam bar is filled with resin. As a result, there is no protrusion of the solder plating to the inside of the dam bar due to the mold clamping pressure, so a good resin-encapsulated semiconductor that does not generate whisker-like solder plating even if the lead terminal is cut or bent. The device can be obtained.

[Brief description of drawings]

FIG. 1 is an example of a time chart of plunger displacement, mold clamping pressure, and molding pressure in a mold resin injection step according to the present invention.

FIG. 2 is a sectional view showing a semiconductor device manufactured according to the present invention.

FIG. 3 is a front view showing an injection molding machine used in the present invention.

FIG. 4 is a perspective view showing the injection molding machine of FIG.

FIG. 5 is a plan view showing a pot, a cavity, and the like provided in the mold.

FIG. 6 is a cross-sectional view showing a semiconductor device at the beginning of the related art.

FIG. 7 is a flowchart showing a manufacturing process for manufacturing the semiconductor device of FIG.

FIG. 8 is a cross-sectional view showing a state in which a conventional PPF is clamped in a mold.

9 is a flowchart showing a manufacturing process for manufacturing the semiconductor device of FIG.

10 is a plan view showing the PPF clamped by a mold in the state of FIG.

11 is a cross-sectional view taken along the line AA ′ in FIG.

FIG. 12 is a view showing a situation in which a beard-shaped solder plating is generated in a conventional semiconductor device using PPF.

[Explanation of symbols]

 6 Semiconductor element 7 Wire 8 Mold resin 10 Mold 11 Upper mold 12 Lower mold 21 PPF 22 Die pad 22a Silver plating 23 Lead terminal 24 Inner lead part 24a Silver plating 25 Outer lead part 29 Solder plating 30 Injection molding machine 31 Base 32 Movable plate 33 Hydraulic cylinder 34 Plunger 35 Displacement measuring device 36 Mold clamping / mold opening control circuit 37 Hydraulic drive device

Claims (3)

[Claims] 1. A semiconductor device in which a lead frame is connected to a semiconductor element, and a part of the lead frame is exposed to the outside to cover the semiconductor element and the lead frame with a molding resin by using a mold. In the method of manufacturing a semiconductor device to be manufactured, as the lead frame, an outer lead portion exposed to the outside of the mold resin is used, which is plated with solder.
A step of setting the lead frame in a mold, clamping the mold with the solder-plated outer lead part sandwiched from both sides, and applying a first pressure; and the mold in the clamped state. The step of injecting the mold resin into the cavity of the mold, and the step of injecting the mold resin into the cavity,
A step of increasing the mold clamping pressure of the mold to a second pressure higher than the first pressure; and a mold resin injected into the cavity after the mold clamping pressure of the mold is increased to the second pressure. And a step of applying a final molding pressure to the semiconductor device. 2. A plunger is used as a means for injecting a mold resin into the cavity of the mold, and the mold clamping pressure of the mold is changed from the first pressure to the second pressure at a timing based on the displacement amount of the plunger. The method for manufacturing a semiconductor device according to claim 1, wherein the pressure is raised to the above pressure. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the solder plating is performed by using a lead frame formed from the outer lead portion to a portion covered with the mold resin.