JPS59190384A - Production of mask plate for partial plating - Google Patents

Abstract

PURPOSE:To obtain a mask plate having an Si resin layer having a smooth surface and exact plating regions by placing a resin substrate provided with holes in the position corresponding to the plating regions on a matrix before the curable Si resin cast into the plating regions of the recess provided thereto cures and stripping the matrix upon curing of the resin. CONSTITUTION:A recess 13 consisting of prescribed plating regions having 0.3- 2.0mm. depth is provided in the bottom 12 of a matrix 10 consisting of a photosensitive resin such as preferably polyester resin. An Si resin 15 curable to the deep part at an ordinary temp. is cast into the recess 13 and the resin on projecting parts 11 is scraped off. The resin 15 is packed up to the height flush with an outside frame 14 and the projecting surface 11. A heat- and chemical resistant resin substrate 17 provided with holes 21 corresponding to said plating regions is placed accurately thereon before the resin 15 cures. After the resin 15 cures, the substrate 17 and the resin 15 are stripped from the matrix 10, and the intended mask plate for partial plating laminated with the Si resin layer 22 on the substrate 17 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a mask plate used when performing partial precious metal plating on the island portion and the tip portion of the inner lead of a lead frame for a semiconductor integrated circuit (hereinafter abbreviated as IC).

IC lead frame is 42 alloy (42% Ni, balance of Fe)
, Cobar # (Ni 29%, Co 17%, Fe balance)
After forming a predetermined pattern by press punching or etching a material with high thermal conductivity and strength such as phosphor bronze, the island part (the part on which the fC chip is mounted) and the inner lead tip part (the wire Conventional mask plates are made of materials such as titanium, stainless steel, tantalum, etc., by partially applying noble metals such as gold, silver, palladium alloy, etc. The configuration shown in Figures 1 and 2 was used.In other words, in Figure 1, a resin substrate (1) with only a predetermined plating area cut out (polypropylene, polyethylene, polyester, glass fiber) was used. The cushion layer (2) is made by spray-coating epoxy resin, glass fiber-containing polyester resin, vinyl chloride resin, silicone resin, etc.This mask plate is easy to make, but it can be made by spraying silicone resin. Due to the coating, the surface is uneven (3), and the silicone resin flows into the plating area (hole) (5), causing protrusion (4).
There was a phenomenon in which . This has caused inconvenience when performing partial plating on an IC lead frame using this mask plate. That is, since the silicon surface of the mask plate has uneven parts (3), the IC
The drawbacks are that the plating solution leaks through the lead frame and deposits expensive precious metals outside the plating area.
), there is a protruding part of silicone resin (4),
There was a drawback that the plating area was smaller than the set plating area. On the other hand, as in the mask board shown in Fig. 2, there is a method in which a silicon sheet (6) is attached to a perforated #Lj resin substrate J, and then the silicon sheet (6) is cut by laser cutting or mechanical punching. There is also. Compared to the method of spray coating silicone resin shown in Fig. 1 described above, the surface is smooth (although it has the advantage that the plating solution does not leak due to force), when punching the silicone sheet (1-f6), ), and it was difficult to accurately identify the plating area, similar to the spray coating method. For this reason, when conventional mask plates are used, more expensive precious metals than necessary are deposited, but conversely, the plating area is small, resulting in the production of many defective products.

In order to improve this situation, the present invention provides a method for manufacturing a mask plate having a silicon layer with a smooth surface and a precise plating area. More specifically, when performing partial plating, as shown in Figure 7, the mask plate (9)
Place the IC lead frame body 08) on top of the IC lead frame body 08), and then sandwich the top rubber (19, l) to prevent liquid leakage during plating.
20) is jetted to perform plating, but in that case, the IC lead frame body (
18) When placed on the plate, the plating solution leaks from the gap. In order to improve this problem, the present invention devises a method for forming the cushion layer (2), which plays an important role in partial plating, by imparting adhesion and cushioning properties to the mask plate (9).

The details of the present invention will be explained based on the drawings.

FIG. 6 shows a master mold (10) for obtaining a silicon layer with a smooth surface and a precise plating area. This matrix θ0)
may be made by cutting using metal materials (aluminum, iron, copper, brass) or plastic materials (vinyl chloride resin, glass fiber-containing epoxy resin), but when making many of the same mold in a short time. It is desirable to use a photosensitive resin. Add an explanation of how to make a matrix using photosensitive resin as the material. As the photosensitive resin, commercially available photosensitive resin plates such as polyester, nylon, and polyvinyl alcohol can be used. For example, the product name of Tokyo Ohka Kogyo■ [Rigil
on j, BASF product name f'nyloprint
J, Mukasei Kogyo■, ``Product Name: APR System G42, Mold 20'', etc. For patterning, a negative mask film is prepared so as to have a finish as shown in FIG. In other words, the depth of the recess 03) of the matrix (10) (corresponding to the thickness of the silicon layer) is 0.3 to 20 mm, and the photosensitive resin plate also needs to be this thick, and generally Under these circumstances, when exposed from one side, the photosensitive resin surface that is in contact with the negative mask film will produce a pattern that matches the accuracy of the negative mask film due to the positional relationship between the light source and the negative mask film. Below 0mm, the luminous flux spreads, so the finished area becomes larger.

The angle of inclination at this time is about 10 to 300, so it is necessary to make the pattern of the negative mask film small in advance so that the area through which the light passes is small. After placing them in close contact with each other and exposing them to ultraviolet light or a chemical lamp for several minutes, apply the specified developer (alcohol, pure water or weak alkaline water).
After development and drying, exposure is performed to form a matrix 0 as shown in
0) is formed. This matrix (10) is 0.3 to 20
At the depth of the plating, the predetermined plating area is at the bottom of the pattern (I
2), and the convex surface (11) is slightly smaller than the bottom portion 02) due to the above-mentioned spread of the light beam. Further, an outer frame (14) is provided to prevent leakage when silicone resin is poured. Curing silicone resin, which is an important part of this method, is poured into the recess (13) of the H-type 00) obtained in this way. Anything is fine, and commercially available products include Shin-Etsu Chemical's cold-curing silicone resin, trade name KE61] (TV, E119RT, KE1).
2RTV, KE112RTV, Toshi Silicone (product name of S I-i 9550, S H9551, S I
Examples include -I 9552, SH9555, SH9556, etc. The silicone resin that has been degassed is placed into a matrix (1
0), scrape off the resin on the convex part 01) with a rubber squeegee, steel doctor, rubber roll, etc., and as shown in Fig. is filled with silicone resin (15). On the other hand, the resin substrate 07) which is the mask base material may be made of any material as long as it has heat resistance and chemical resistance as in the conventional method, such as polypropylene, polyethylene, polyester, epoxy resin containing glass fiber, polyester resin containing glass fiber, chloride resin, etc. Vinyl is a possible candidate. The hole (2+) (plating area) provided in this resin substrate 07) is
When using the above-mentioned photosensitive resin plate as a matrix for forming a silicon layer, for the reasons mentioned above, the area is set slightly smaller than the predetermined area, and the pattern convex surface (11) of the matrix shown in Fig. 6 is set.
It must be the same area as. A primer (for example, Primer T from Shin-Etsu Chemical Co., Ltd.) is applied as necessary to the resin substrate 07) provided with the holes (21), and the surface 06) of the silicone resin (15) is placed in the above matrix (10). With the silicone resin (15) at the same height as the convex surface (11) and still in an uncured state where the silicone resin (15) maintains its fluidity, stack the resin substrates (07) as shown in Figure 5. . From the top of the resin substrate 07), several 100 to several kg/cr
A pressure of y is applied and the resin is left to stand until the predetermined curing time of the silicone resin (15) is reached. Silicone resin (1
After 5) has hardened, silicone resin (15
) is peeled off while it is stuck to the resin board (17),
As shown in Fig. 6, a mask plate with a smooth surface of the silicone resin layer (22+) and an accurate plating area, which is the purpose of this method, can be obtained. Using this mask plate, an IC lead frame (( When selective precious metal plating (gold, silver, palladium alloys, etc.) is applied, the plating film spreads to unnecessary areas, resulting in a large amount of material savings. By using a mask plate, the plating area is small (less than 5 mm on one side).
Items that could not be plated in patterns can now be easily plated, and can now be applied to all kinds of products.

Example As a matrix material, a photosensitive resin plate (manufactured by Tokyo Ohka Kogyo, part name: Rigilon MX1-100) was used.

As a negative film, the light transmitting area (corresponding to the hole in the mask plate) is 0.6 mm per side from the predetermined plating area.
A small square pattern (5 pieces lined up with each side of 9.2 rpm and pitch of 15 rrrIn) was used.

Bring the negative film into close contact with the resin plate and apply chemical force) L/
77p (wavelength 250-430mm, 4 ow, distance 4
, 5 cm) for 25 minutes. The phenomenon was carried out using tap water at 40°C using a single spray method. 90'c
After drying, post-exposure was performed again for 1 minute using the chemical lamp described above to complete a matrix (QO).

As shown in Figure 3, this matrix has a convex surface (1
1) and a pattern with the bottom (12+) of 10rrtm was formed and its relief depth was o68#. Next,
Pour the blended and defoamed silicone resin (Shin-Etsu Chemical Co., Ltd. KE61RTV) into this mother mold (00) and use a steel doctor to make it at the same height as the pattern convex surface θ1) of the mother mold (10) as shown in Figure 4. Remove excess silicone resin (1
5) was scraped off. While the poured silicone resin (15) still maintains fluidity, overlap the resin substrate sides prepared in advance and apply a pressure of soog/;7 and leave at room temperature for 24 hours, which is the time required for the resin to harden. I let it happen. The resin substrate (17) is made of vinyl chloride with a thickness of 5 mm, and the size of the hole corresponding to the plating area is a square with 92 scales on one side on the side in contact with the silicone resin (15). After the silicone resin has completely hardened, when the silicone resin (15) is peeled off from the mother mold 00) while it is stuck to the resin substrate α7), the surface of the silicone resin layer (22) is smooth and accurate as shown in Figure 6. A mask plate (9) with unplated areas was obtained.

Using this mask plate (9), gold plating with a thickness of 25 μm was performed on a 42 alloy lead frame under the conditions shown in Table 1.

As a result, the plating area was obtained with an error within 10 μm from the set value (conventionally, it was 100 to 200 μm), and a good quality product with no plating leakage was obtained. At the same time, it also contributed significantly to saving expensive money.

Table 1 Selective gold plating conditions

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional partial plating mask plate formed by spray coating with silicone resin. FIG. 2 is a sectional view showing an example of a conventional mask plate for partial plating formed by laminating silicon sheets. FIG. 6 is a perspective view showing an example of a matrix for pouring the silicone resin which is the cushion of the mask plate of the present invention, and FIG. 4 is a perspective view showing the matrix into which the silicone resin of the present invention is poured. FIG. 5 is a sectional view showing a state in which a resin substrate is superimposed on a mother mold into which the silicone resin of the present invention is poured (10)...Mother mold 01)...Convex surface 02) ...bottom α3) ...concavity 0 force・
・・Outer frame (15)・・Silicone resin 06)・・・
・Silicon resin surface 07)...Resin substrate 0
υ...hole (22)...7L pieces of silicone resin layer

Claims (2)

[Claims] (1) Pour a curable silicone resin (15) into a matrix αO having a convex surface (11) corresponding to the plating area,
While the silicone resin (151) is in an uncured state, α force is applied to a resin substrate provided with holes (21) corresponding to predetermined plating areas with high accuracy, and after the silicone resin (15) is cured, the mother mold 00 ) A method for manufacturing a mask plate for partial plating comprising a silicone resin layer laminated on a resin substrate aη. (2) The method for manufacturing a mask plate for partial plating according to claim 1, wherein a photosensitive resin plate is used as a matrix having a convex surface corresponding to the plating area.