JPH0841677A - Plating method and its equipment - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a plating method and apparatus capable of uniformly and quickly performing solder plating on an external lead of a semiconductor device. [Structure] Semiconductor device 10A immersed in plating solution L
When the outer lead 11b is plated, the semiconductor device 10A is moved in a two-dimensional plane, a plating tank 1 containing a plating solution L, and a plating solution in the plating tank. Device 10A immersed in water
In the plating apparatus, a holding body 15 for holding the holding body and a robot 24 for moving the holding body in a two-dimensional plane are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating method and apparatus for plating an outer lead of a semiconductor device, for example.

[0002]

2. Description of the Related Art For example, when manufacturing a semiconductor device,
There are the following manufacturing processes. That is, a semiconductor element (chip) is die-bonded on the lead frame, and the terminals formed on the semiconductor element and the internal lead of the lead frame are wire-bonded. Then, the semiconductor element is sealed with a resin to form a semiconductor device, and an external lead of the lead frame protruding from the sealing portion of the semiconductor device is formed.
The semiconductor device is punched out from the lead frame after the solder is plated on the lead frame.

Solder plating for the external lead is as follows.
When mounting the semiconductor device on a mounting board, it is common to print a cream solder on the footprint of the mounting board. It is done to measure the improvement of sex.
Also, by plating the outer leads with solder, the corrosion resistance can be improved.

With the recent increase in density of semiconductor devices,
The number of external leads is increasing (increasing the number of pins), and the direction of the external leads is not limited to one side or both sides of the sealing part depending on the type of semiconductor device, but from the four sides like QFP. Some have been derived. As described above, the semiconductor device has different numbers of external leads and different protruding directions of the external leads, and the semiconductor devices are formed in two rows in one lead frame. In any case, there is a demand for uniform and rapid plating of solder on the outer leads in order to improve productivity and quality.

In order to quickly form a uniform plating layer, it is effective to reduce the thickness of the diffusion layer on the surface of the outer lead in the plating solution. Therefore, in the prior art, for example, as shown in Japanese Utility Model Laid-Open No. 52-147115, the object to be plated is moved only in the vertical direction by a piston-crank mechanism, whereby the external releasability is increased.
It was done to reduce the thickness of the diffusion layer on the surface of the window.

By moving the object to be plated in the vertical direction, the thickness of the diffusion layer on the surface of the object to be plated can be made thinner than in the case where it is not moved. However, if the object to be plated is only moved in the vertical direction when the object to be plated is, for example, a semiconductor device, the flow of the plating solution on the surface of the external lead protruding in the direction parallel to the direction of movement is prevented by the sealing portion. Easy to be disturbed. Further, when the outer lead is orthogonal to the moving direction, the widthwise end face of the outer lead impedes the flow of the plating solution.

As a result, the thickness of the diffusion layer on the surface of the outer lead is less likely to decrease uniformly, and plating may not be performed uniformly and quickly. In particular, when the object to be plated is a QFP in which external leads are projected in four directions, or when the semiconductor devices are formed in two rows on one lead frame, such a tendency tends to occur. It will be noticeable.

[0008]

As described above, by simply moving the object to be plated in the vertical direction, the thickness of the diffusion layer is uniformly reduced over the entire surface of the part to be plated when the shape becomes complicated. Since it is difficult to do so, there are cases where plating cannot be performed uniformly and quickly.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a plating method and apparatus capable of uniformly reducing the thickness of the diffusion layer over the entire surface of the object to be plated. To provide.

[0010]

The present invention resides in a plating method characterized in that when an object to be plated immersed in a plating solution is plated, the object to be plated is moved in a two-dimensional plane. Further, according to the present invention, in a plating apparatus for plating an object to be plated, a plating tank containing a plating solution and a holding mechanism for holding the object to be plated immersed in the plating solution in the plating tank. And a driving means for moving the holding mechanism in a two-dimensional plane.

[0011]

According to the above invention, since the object to be plated moves in a two-dimensional plane in the plating solution, the fluidized stirring of the plating solution on the surface of the object to be plated is made uniform, so that the thickness of the diffusion layer is made uniform. Can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The plating apparatus shown in FIGS. 1 and 2 includes a plating tank 1 containing a plating solution L. A base plate 2 is provided on the inner bottom portion of the plating tank 1, and a pair of support plates 3 are provided upright on the base plate 2 in parallel at predetermined intervals. An opening 3a is formed in one support plate 3. A back plate 5 holding the anode 4 and a mask plate 6 are attached and fixed to each support plate 3 with screws 7.

The back plate 5 and the mask plate 6 are made of an insulating material, and the anode 4 is a net-like one in which a thin plate of titanium or the like is clad with platinum foil to form a roll lath shape. Openings 5a and 6a are formed in the back plate 5 and the mask plate 6, respectively, and the anode 4 is provided with a part thereof exposed from the opening 6a.

As shown in FIG. 2, one end of a circulation line 8 is connected to the bottom of the plating tank 1. This circulation line 8
A pump 9a is provided at an intermediate portion, and the other end is connected to a nozzle 9b arranged so as to face the opening 3a of the one support plate 3 in the plating tank 1. Therefore, if the anode 4 has a mesh-like shape, the plating solution L ejected from the nozzle 9a is activated by operating the pump 9a, and the plating solution L is discharged from the opening 3a of the support plate 3, the opening 5a of the back plate 5, the anode 4 and It passes through the opening 6 a of the mask plate 6.

The nozzles 9a are provided on the back sides of the two support plates 3 and the openings 3a and 5a are formed in each of the pair of support plates 3 and the back plate 5, so that the pair of anodes 4 are plated with the plating solution. L may be distributed.

In this embodiment, the object to be plated by soldering is, as shown in FIG.
A SOJ type semiconductor device 10A having external leads 11b led out from both sides of the external lead 1a.
When solder plating b, the anode 4 is formed in a shape having a pair of strip portions 4a facing the outer leads 11b on both sides of the mold portion 11a.
a is exposed from the opening 6a.

As shown in FIG. 4 (b), the semiconductor device 10B is provided with an external lead 11 from four directions of the mold part 11a.
In the case of the QFP type in which b is derived, the anode 4A may be formed in a rectangular frame shape that faces the outer leads 11b in four directions as shown in FIG. In the case of other types of semiconductor devices, the anode may have a shape facing the external leads led out from the mold portion of each semiconductor device.

A holder 15 for holding the semiconductor device 10A is provided between the pair of support plates 3. The holding body 15 has a pair of mask plates 16 for holding the peripheral portion of the lead frame 17 of the semiconductor device 10A. Each mask plate 16 has a mold portion 11a of the semiconductor device 10A.
And an external lead 11 formed on the lead frame 17
An opening 16a is formed to expose a portion to be b. The inner peripheral surface of the opening 16a is formed as a taper surface inclined outward toward the outer surface side so as not to hinder the flow of the plating liquid L during driving.

In this embodiment, the semiconductor device 10A held by the holding body 15 is in a state before being punched out from the lead frame 17, and for convenience of explanation.
The lead frame 17 of the semiconductor device 10A is shown in FIG.
From the long lead frame 17A to 1 as shown in FIG.
It has a length corresponding to one semiconductor device 10A and is separated.

As is well known, since a plurality of semiconductor devices 10A are formed in one row or a plurality of rows (one row in FIG. 5A) on the long lead frame 17A, in an actual plating operation. Solder plating is simultaneously performed on the external leads 11b of the plurality of semiconductor devices 10A without separating the long lead frame 17A into the minimum length of each semiconductor device 10A. In that case, FIG.
As shown in (b), the anode 4B may be formed in a strip shape in which a plurality of strip portions 4a facing the outer lead 11b of each semiconductor device 10A are continuously provided.

As shown in FIG. 3B, one mask plate 16 of the holder 15 is engaged with a jig hole 18 of the lead frame 17 to position the lead frame 17. With a pair of pins 19 protruding from it, and with a pair of mask plates 16
Through holes 21 through which the screws 19 for joining and fixing the mask plates 16 are inserted are formed at the four corners.

A lead frame is provided by a pair of mask plates 16.
When the frame 17 is held, a cathode 22 made of a metal piece such as stainless steel is provided between one of the mask plates 16 and the lead frame 17 so as to be electrically connected to the lead frame 17. .

Lead wires 23 are connected to the anode 4 and the cathode 22, respectively, and the lead wires 23 are connected to the positive and negative sides of a DC power source (not shown).
As shown in FIGS. 1 and 2, the holding body 15 is driven by a robot 24 as a drive mechanism. That is, the robot 24 has an arm 24a, and a hand 25 is provided at the tip of this arm 24a. Then, the holding body 15 is detachably held by a pair of fingers 26 provided on the hand 25.

Normally, the hand 25 of the robot 24 is driven in a three-dimensional direction by a drive source (not shown). However, when the outer lead 11b of the semiconductor device 10 is plated with solder, the hand 25 is provided with the pair of support plates. It is driven in the vertical and horizontal directions between the three, that is, in the two-dimensional plane direction of the horizontal direction indicated by X and the vertical direction indicated by Z in FIG. By combining various movements in the X direction and the Z direction, the hand 25 can be moved along various loci such as a circular shape and a rectangular shape on a two-dimensional plane.

In the plating apparatus having the above structure, when solder plating is applied to the outer lead 11b of the lead frame 17 of the semiconductor device 10A, first, the anode 4 and the cathode 22 are energized to operate the robot 24. Then, the holding body 15 is two-dimensionally moved between the pair of support plates 3 in the X direction and the Z direction. In this case, the holding member 15 is placed in a range in which the pair of strip-shaped portions 4a of the anode 4 are not largely deviated from the outer lead 11b and are not in the non-opposing state, that is, in the range in which the opposing state of the anode 4 and the strip-shaped portion 4a is not removed. Dimensional plane motion.

By moving the holder 15 in a two-dimensional plane, the plating solution L relatively flows on the surface of the outer lead 11b of the lead frame 17 of the semiconductor device 10. If the semiconductor device 10A is circularly moved by controlling the movements of the two-dimensional plane motion in the X and Z directions, the external lead 1
The plating liquid L can be made to flow relatively evenly with respect to the surface of 1b. Therefore, since the thickness of the diffusion layer on the surface of the outer lead 11b is uniformly reduced, the solder plating on the outer lead 11b can be uniformly and quickly performed.

For example, the SOJ type semiconductor device 10A shown in FIG. 4A is mounted in the Z direction (vertical direction) as in the conventional case.
If only the external lead 11b is driven, the external lead 11b extends in the direction orthogonal to the driving direction.
In some cases, the widthwise end face of b may impede the flow of the plating solution L and may not flow relatively uniformly over the entire surface.

When driven only in the X direction orthogonal to the Z direction, the flow of the plating solution L is not obstructed by the influence of the end surface in the width direction of the outer lead 11b, but the width of the mold portion 11a. Both side surfaces in the direction may impede the relative flow of the plating solution L on the surface of the outer lead 11b.

Further, in the case of the QFP type semiconductor device 10A shown in FIG. 4 (b), in either the Z direction or the X direction, if there is only one direction, the end face of the external lead 11b and Due to the influence of the side surface of the mold part 11a, the relative flow of the plating solution L becomes difficult to be uniform.

Therefore, if the semiconductor device 10A is driven in one of the Z direction and the X direction, it is difficult to uniformly and quickly thin the diffusion layer on the surface of the external lead 11b. Solder plating on the surface cannot be performed uniformly and quickly.

However, the present invention is directed to the semiconductor device 1
0A is caused to move in a two-dimensional plane in which the Z direction and the X direction are combined. Therefore, if the two-dimensional plane motion is, for example, a circular motion, the relative flow of the plating solution L on the surface of the outer lead 11b is caused by the end face in the width direction of the outer lead 11b and the mold portion 11a. Since it is difficult to be affected by the side surface, it is easy to make uniform.

As a result, the diffusion layer on the surface of the outer lead 11b can be thinned uniformly and quickly.
Solder plating on the outer lead 11b can be performed uniformly and quickly. Especially, the object to be plated is QFP
When the semiconductor devices are provided in two rows in the semiconductor 10B of the type or in one lead frame, the effect of the two-dimensional plane movement becomes remarkable.

Since the anode 4 has a mesh shape, the plating solution L ejected from the nozzle 9a in the plating tank 1 toward one of the anodes 4 passes through the anode 4 and is a semiconductor device 10A to be plated. Collide with the surface of the outer lead 11b. Therefore, since the stirring effect of the plating liquid L is improved,
This also makes it possible to perform plating uniformly and quickly.

Further, the anode 4 is divided into a plurality of strip portions 4a facing the outer leads 11b in each row of the semiconductor device 10A. Therefore, as shown in FIG. 6A, the strip portion 4a faces the outer lead 11b, and the semiconductor device 10A is driven to be displaced as shown in FIG. 6B. The density of the current flowing between the strip-shaped portions 4a and the outer leads 11b in each row is kept uniform.

In FIG. 6C, the anode 4B is connected to the external lead 11b.
In the case where the semiconductor device 10A is not divided into a plurality of strip-shaped portions 4a in a sheet shape having a size facing the entire semiconductor device 10A, in that case, no current flows in the mold portion 11a. The current density at the base end portion of the outer lead 11b increases. In other words, the current density on the surface of the outer lead 11b becomes non-uniform, which may make it difficult to perform solder plating uniformly.

Further, since the lead frame 17 is held and fixed between the pair of mask plates 16, even if the lead frame 17 is thin and has low rigidity, the robot 24 With this, it is possible to surely perform a two-dimensional plane motion.

In the above embodiment, the semiconductor device 10A is used.
Although only the holding body 15 holding the
Along with the holding body 15, the anode 4 side may also be moved in a two-dimensional plane. By doing so, the anode 4 is provided with a stroke in the Z direction and an X direction of the two-dimensional plane motion of the semiconductor device 10A.
Since the same facing state is maintained with respect to the outer lead 11b regardless of the speed, it is possible to further improve the speed and uniformity of solder plating.

Further, the driving means for moving the holding body 15 in a two-dimensional plane is not limited to the robot 24, but may be a cam mechanism, a link mechanism, or a combination of these mechanisms. It should be a plane movement. Further, the object to be plated is not limited to the semiconductor device, and needless to say, may be another object.

[0039]

As described above, according to the present invention, when plating the object to be plated immersed in the plating solution, the object to be plated is moved in a two-dimensional plane. Therefore, the plating liquid can be relatively uniformly flowed on the surface of the object to be plated, and the thickness of the diffusion layer can be uniformly and quickly reduced. Therefore, the plating on the object to be plated can be uniformly and quickly performed. It will be possible.

[Brief description of drawings]

FIG. 1 is a front view of the overall configuration of an embodiment of the present invention.

FIG. 2 is a side view of the same.

FIG. 3A is an exploded perspective view of the anode side, and FIG. 3B is an exploded perspective view of the holding body.

4A is a perspective view of an SOJ type semiconductor device, FIG.
(B) is a perspective view of a QFP type semiconductor device,
FIG. 3C is a perspective view of an anode for a QFP type semiconductor device.

5A is a plan view of a lead frame, and FIG. 5B is a plan view of an anode used in the lead frame.

6 (a) and 6 (b) are explanatory views of the flow of current between the anode and the external lead of the present invention, and FIG. 6 (c) is a view of the current between the conventional anode and the external lead. Explanatory drawing of a flow.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plating tank, 10A, 10B ... Semiconductor device (object to be plated), 11b ... External lead (object to be plated), 15 ... Holding body, 24 ... Robot (driving means), L ... Plating liquid.

Claims (2)

[Claims] 1. A plating method, which comprises two-dimensionally moving an object to be plated when the object to be plated immersed in a plating solution is plated. 2. A plating apparatus for plating an object to be plated, comprising: a plating tank containing a plating solution; and a holding mechanism for holding the object to be plated immersed in the plating solution in the plating tank. And a drive means for moving the holding mechanism in a two-dimensional plane.