JP3404702B2 - Manufacturing method of mask plate for partial plating - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a masking plate for partial plating for partially plating a lead frame for a semiconductor device.

[0002]

2. Description of the Related Art A lead frame for a semiconductor device is usually plated with a noble metal such as gold or silver for the purpose of improving electrical characteristics. However, since such a precious metal material is expensive, in recent years, it is general to mask unnecessary portions and perform plating treatment only on the truly necessary portions.

FIG. 7 is a diagram showing a semiconductor device lead frame. The lead frame 1 includes a pad 2 for mounting a semiconductor element and a support bar 3 for supporting the pad 2.
An inner lead 4 arranged around the pad 2 and extending radially, and a tie bar 5 connecting the inner lead 4 with each other.
And an outer lead 6 connected to each of the inner leads 4 and a frame body 7 connecting the outer leads 6. Of these, usually, the plating 8 made of a noble metal such as gold or silver is applied only to one surface of the tip 2 of the pad 2 for mounting the semiconductor element and the inner lead 4 for wire bonding. In addition, in the normal manufacturing process, the lead frame 1 is formed in a belt-shaped or short-shaped state in which a plurality of lead frames are connected, and each process is performed.

FIG. 6 shows a mask plate used for masking such partial plating. The mask plate 9 shown here is for subjecting a lead frame formed in a strip shape or a short shape to a plating treatment, that is, the mask plate 9 is a glass plate provided with a plurality of openings 10 corresponding to the pattern of the lead frame. The mask plate 11 is made of a hard material having heat resistance and chemical resistance such as epoxy resin, and the elastic member 12 made of silicon rubber or the like is attached to the surface of the mask plate 11 that contacts the object to be plated. .

Next, a partial plating method using such a mask plate 9 will be described. As shown in FIG. 4, first, the mask plate 9 is mounted on the top plate 13. In addition,
The top plate 13 also has a plurality of openings 10 corresponding to the openings 10 provided in the mask plate 9.
Is provided. The elastic member 1 of the mask plate 9
The surface of the lead frame 1a formed in a strip shape on 2 is placed in contact with the surface to be plated, and the non-plated surface of the lead frame 1a is provided with a pressing plate 14 to prevent the plating solution from wrapping around to the back surface. The lead frame 1a is sandwiched by abutting the elastic member 15 provided on the abutting surface of the object to be plated.

In this state, pressure is applied to the elastic members 12 and 15 of the mask plate 9 and the pressing plate 14, respectively, to the lead frame 1.
The area of the lead frame 1a that does not require plating is masked by closely contacting a. At this time, the plating required area of the lead frame 1a, that is, the surfaces to be plated of the pads 2 and the inner leads 4 of the lead frame 1a are not masked, and as shown in FIG.
It is projected in 0. Then, a plating liquid is ejected into the opening 10 from a nozzle (not shown) corresponding to the plurality of openings 10 provided in the mask plate 9, whereby the lead projected into the opening 10. In the required area of the plated surface of the frame 1a, in this example, the tip portions of the pad 2 and the inner lead 4 described above,
The plating 8 is applied to a desired thickness.

The mask plate 9 used for such partial plating is generally manufactured by a molding method using a mold. As an example of a conventional method for manufacturing the mask plate 9, first, as shown in FIG. 5A, a liquid such as a room temperature curable liquid silicone rubber is placed in a recess of a mold plate 16 made of a metal material such as SK-3. The elastic material 12a is poured. The mold plate 16 is provided with a plurality of convex portions 17 corresponding to the plating area.

Then, as shown in FIG. 5B, a mask plate 11 made of glass epoxy resin or the like is placed thereon so that the contact surface side of the object to be plated contacts the mold plate 16. At this time, the protrusion 17 of the mold plate and the opening 10 of the mask plate are positioned so as to overlap each other. Then, these are pressed by an L-shaped clamp or a mold device (not shown), and in this state, at room temperature for about 17 to 24
The liquid elastic material 12a is left to cure for about an hour. After that, when the liquid elastic material 12a is cured, the mold plate 16 and the mask plate 11 are peeled off,
The above-mentioned mask plate 9 in which the elastic member 12 made of silicon rubber is mounted on the surface of the mask plate 11 that contacts the object to be plated.
Is obtained.

According to such a manufacturing method, the mask plate 9 having the masking elastic member 12 having the same size as the mold plate 16 can be obtained. However, when actually performing plating, the lead frame 1a is mainly subjected to tension applied during positioning during plating and thermal expansion due to exposure to a plating solution that is normally controlled to a high temperature of 60 ° C to 65 ° C. Extension may occur in the longitudinal direction, and as a result, an error may occur in the pitch between the lead frame 1a and the plating area of the mask plate 9.

[0010]

When an error occurs in the pitch of the plating area between the lead frame 1a and the mask plate 9 as described above, it is possible to plate the desired plating area as shown in FIG. I can not do it, and defective products occur frequently. As described above, since the precious metal plating material is expensive, the defect here causes enormous damage.

Further, when such an error occurs, the pitch cannot be controlled in the conventional manufacturing method. Therefore, the mold plate 16 itself has to be recreated to correct the error, which is troublesome and costly. Was becoming. The present invention has been made in view of the above circumstances, and is a portion that solves the above-mentioned problems and can perform favorable partial plating by arbitrarily adjusting the pitch difference of the plating area between the lead frame and the mask plate in partial plating. It is an object of the present invention to provide a method for manufacturing a plating mask plate.

[0012]

In order to achieve the above object, in the mask plate for partial plating of the present invention, a curable liquid elastic material is poured into a mold plate, and the mask plate is placed on top of this. The elastic member is attached to the mask plate by pressurizing these by heating with a mold apparatus having a heating mechanism for each of the upper mold and the lower mold to cure the liquid elastic material.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The mask plate for partial plating of the present invention will be described below in detail with reference to the drawings. The same parts as in the conventional example will be described using the same reference numerals. In this embodiment, the structure of the mask plate is the same as that of the conventional example, that is, the mask plate 9 has a plurality of openings 1 corresponding to the pattern of the lead frame 1a.
A mask plate 11 made of a hard material having heat resistance and chemical resistance such as glass epoxy resin provided with 0, and mounted on a surface of the mask plate 11 that contacts the object to be plated,
The mask plate 11 and the elastic member 12 made of silicon rubber or the like having a plurality of openings 10 are formed.

Such a mask plate 9 is manufactured by a molding method using a mold as in the conventional case. That is, FIG.
As shown in (a), first, a liquid elastic material 12a such as a room temperature curable liquid silicone rubber is poured into the recess of the mold plate 16 made of a metal material such as SK-3. The mold plate 16 is provided with a plurality of convex portions 17 corresponding to the plating area. Then, as shown in FIG. 5B, a mask plate 11 made of glass epoxy resin or the like is formed on the mold plate 1 on the side to be plated.
Place it so that it touches 6. At this time, the protrusion 17 of the mold plate and the opening 10 of the mask plate are positioned so as to overlap each other.

In this state, in the present invention, the mold plate 16 and the mask plate 11 are pressurized by using the mold device 18 as shown in FIG. The mold apparatus 18 used in the present invention is provided with heating mechanisms 21a and 21b in the upper mold 19 and the lower mold 20, respectively, and these can independently adjust the temperature. In this embodiment, the mold plate 16 is brought into contact with and placed on the lower die 20 of the mold device 18, and the upper die 19 is brought into contact with the mask plate 11.

An example of a method of manufacturing the mask plate 9 using the mold device 18 will be described below. In this example, the plate thickness is 0.
Fe-called alloy 42 having a width of 25 mm and a width of 70 mm
A mask plate 9 was manufactured for the purpose of partially plating the lead frame 1a made of a Ni alloy material. The mask plate 11 used in this example is 490 × 90 × 1.5 (m
m) made of glass epoxy resin material, and the mold plate 16 is 480 × 90 × 15 (mm) SK
-3 material, and the liquid elastic material 12a is a room temperature curable liquid silicone rubber. Aiming to extend the mask plate 9 by about 25 μm in the longitudinal direction, the temperature of the heating mechanism 21a of the upper mold 19 is set to 170 ° C. and the temperature of the heating mechanism 21b of the lower mold 20 is set to 140 ° C. Pressurized with pressure for 4 minutes. The mask plate 9 was stretched twice under the same conditions, and the first stretch of the mask plate 9 was 23 μm.
m was 30 μm for the second time.

A heating mechanism 21 for the upper mold 19 and the lower mold 20.
The set temperatures of a and 21b are approximately 130 ° C to 250 ° C.
Within the range, each is arbitrarily set in consideration of the material of the mask plate 11 and the mold plate 16 and a desired correction value. In the present invention, the longitudinal elongation of the mask plate 9 can be corrected within a range of approximately 200 μm with respect to the entire length of the mask plate 9, depending on the material, and the error is within ± 20 μm. is there. Needless to say, the pressure and the heating time for pressurizing the mold device 18 can be appropriately changed depending on the material used.

After this, when the liquid elastic member 12a is completely hardened, the mold plate 16 is peeled off from the mask plate 11 to attach the elastic member 12 made of silicon rubber to the surface of the mask plate 11 that contacts the object to be plated. The mask plate 9 is obtained.

The partial plating method using such a mask plate 9 is similar to the conventional method, that is, the mask plate 9 is first mounted on the top plate 13 as shown in FIG. The top plate 13 also has a mask plate 9
Similarly, a plurality of openings 10 corresponding to the plurality of openings 10 provided in the above are provided. Then, the strip-shaped lead frame 1a is placed on the elastic member 12 of the mask plate 9 so that the surface to be plated of the lead frame 1a is in contact with the surface of the lead frame 1a. The lead frame 1a is sandwiched by abutting the elastic member 15 provided on the object contact surface of the pressing plate 14 so as not to go around.

In this state, pressure is applied, and the elastic members 12 and 15 of the mask plate 9 and the pressing plate 14 are respectively applied to the lead frame 1.
The area of the lead frame 1a that does not require plating is masked by closely contacting a. At this time, the plating required area of the lead frame 1a, that is, the surfaces to be plated of the pads 2 and the inner leads 4 of the lead frame 1a are not masked, and as shown in FIG.
It is projected in 0. Then, a plating liquid is ejected into the opening 10 from a nozzle (not shown) corresponding to the plurality of openings 10 provided in the mask plate 9, whereby the lead projected into the opening 10. In the required area of the plated surface of the frame 1a, in this example, the tip portions of the pad 2 and the inner lead 4 described above,
The plating 8 is applied to a desired thickness.

Here, in actual plating, the lead frame 1a may be slightly elongated in the longitudinal direction due to the temperature of the plating solution or the tension applied to the lead frame 1a during positioning of the plating. Since the mask plate 9 is adjusted according to the extension of the lead frame 1a, the lead frame 1
Even if the extension of a occurs, there is no error in the pitch of the plating area between the lead frame 1a and the mask plate 9, and the plating area does not shift, so that good plating can be performed. Further, even if such a pitch error of the plating area suddenly occurs during plating, it is only necessary to perform the work of reattaching the elastic member 12 of the mask plate 9 using the mold device 18 described above. There is no need to take the trouble of recreating the mold plate 16 as in the conventional case.

In the present embodiment, the example in which the lead frame 1a is formed in a strip shape has been described, but the present invention is not limited to this, and the present invention can be applied to a case where it is formed in a short shape. Further, although the lead frame of the type in which the leads extend in four directions has been described in the present embodiment, the present invention is not limited to this, and the lead frame may be extended in one direction or two directions. The invention is applicable. Further, as for the material of the lead frame 1, the present invention can be applied to not only the alloy 42 material used in the present embodiment but also copper material, for example.

Further, in the present embodiment, the glass epoxy resin material is used as the material of the mask plate 11, but the material is not limited to this, and any other material can be used as long as it can satisfy chemical resistance, heat resistance and insulation. It can also be replaced by the material. As for the material of the elastic member 12, urethane, fluorine-based resin, synthetic rubber, natural rubber, etc. may be used as long as it is a liquid elastic material at room temperature or thermosetting, other than the room temperature curable silicone rubber used in the present embodiment. Applicable. Further, as the material of the mold plate 16, a metal material other than SK-3 used in the present embodiment, such as an aluminum material, or a resin material such as a glass epoxy resin may be used.

[0024]

As described above, according to the method for manufacturing the mask plate for partial plating of the present invention, the influence of the temperature of the plating solution during the partial plating, the tension applied to the lead frame during the positioning of the plating, etc. Even if the lead frame stretches due to the plating conditions, the error in the pitch of the plating area between the lead frame and the mask plate can be easily adjusted in advance or at any time.
Even with such extension of the lead frame, it is possible to perform good plating without causing a shift in the plating area.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a deviation of a plating area, which is a problem of the conventional technique.

FIG. 3 is a sectional view showing a partial plating method.

FIG. 4 is a diagram showing a partial plating apparatus and method.

FIG. 5 is a diagram showing a method for manufacturing a mask plate.

FIG. 6 is a view showing a mask plate.

FIG. 7 is a diagram showing a lead frame for a semiconductor device.

[Explanation of symbols]

1,1a lead frame 2 pads 3 Support bar 4 inner lead 5 tie bars 6 outer leads 7 frame 8 plating 9 Mask board 10 openings 11 Mask plate 12 Elastic member 12a Liquid elastic material 13 Top plate 14 Press plate 15 Elastic member 16 Mold plate 17 convex 18 Mold equipment 19 Upper mold 20 Lower mold 21a, 21b heating mechanism

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-59-190384 (JP, A) JP-A-9-209190 (JP, A) JP-A-8-319596 (JP, A) JP-A-7- 88980 (JP, A) JP-A-3-291394 (JP, A) JP-A-3-219084 (JP, A) Actually open 59-40362 (JP, U) Actually open 1-87165 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 5/02 C25D 7/12 H01L 23/50

Claims (2)

(57) [Claims] 1. A method for manufacturing a mask plate for partial plating, wherein an elastic member is provided on a surface of a mask plate to be contacted with an object to be plated, wherein the mask is placed on a liquid elastic material at room temperature or thermosetting which is poured into a mold plate. The plate is placed, each of the upper mold and the lower mold is equipped with a heating mechanism, and the upper mold and the lower mold are independently pressurized while being heated by a mold device heated to an arbitrary temperature, A method for manufacturing a mask plate for partial plating, characterized in that a liquid elastic material is cured and the elastic member is attached to the mask plate. 2. The upper mold and the lower mold are heated to different temperatures.
A method for manufacturing a mask plate for partial plating as described.