JPH0633297A - Electroforming method - Google Patents

Abstract

PURPOSE:To effectively prevent the discoloration and elution of a plating metal layer by depositing a plating metal layer on a metallizing metal layer deposited on the inner surface of the recess of a ceramic body to completely cover the surface of the metallizing metal layer and eliminating the battery action and crevice corrosion of the plating metal layer. CONSTITUTION:The ceramic body 1' with the diameter of the opening increased outward, having a recess 2' and with the inner surface coated with a metallizing metal layer 4' is prepared, the ceramic body 1' is dipped in a plating soln. 8, then an electric field is impressed on the metallizing metal layer 4', and plating metal layers 6 and 7 are deposited on the outer surface of the metallizing metal layer 4'.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an electrolytic plating method,
More specifically, the present invention relates to an improvement in a method for depositing a plated metal layer on the outer surface of a metallized metal layer deposited on the inner surface of a recess of a ceramic body by electrolytic plating.

[0002]

2. Description of the Related Art Conventionally, a semiconductor element housing package for housing a semiconductor element, particularly a semiconductor integrated circuit element, is made of an electrically insulating material such as alumina ceramics, as shown in FIG. A cavity A for accommodating the above, and tungsten, molybdenum led out from the periphery of the cavity A through the side surface to the bottom surface
It is composed of a ceramic insulating base 11 having a plurality of metallized metal layers 12 made of high melting point metal powder such as manganese, and a lid 13. A semiconductor element 14 is provided on the bottom surface of the cavity A of the insulating base 11 with a glass, resin, It is fixed via an adhesive such as a brazing material, and each electrode of the semiconductor element 14 is electrically connected to the metallized metal layer 12 via a bonding wire 15, and then a lid 13 is placed on the upper surface of the insulating base 11. Glass,
Insulating substrate 11 is bonded through a sealing material such as resin or brazing material.
A semiconductor device as a product is obtained by hermetically housing the semiconductor element 14 in a container composed of a lid 13 and a lid 13.

In the package for housing a semiconductor element, when the metallized metal layer 12 is brazed to an external electric circuit board, the brazed strength is increased and the metallized metal layer 12 is effectively prevented from being oxidized and corroded. In order to do so, usually, the exposed metal surface of the metallized metal layer 12 is sequentially plated with plated metal layers 16 and 17 made of nickel and gold by an electrolytic plating method.

In the conventional package for accommodating semiconductor elements, the insulating substrate 11 is generally manufactured by the method described below.

That is, as shown in FIG. 4, first, three large-area unfired ceramic sheets (ceramic green sheets) 21, 22, and 23 are prepared, and provided on the surfaces of the sheets 22 and 23 and the sheets 22 and 23. Metal paste on the entire inner surface of the through hole 24
Apply 25 by printing.

Next, these sheets 21, 22 and 23 are laminated to obtain a raw ceramic body 26 and fired at a high temperature to form a fired ceramic body 26 'and a metallized metal layer 12.

Then, the fired ceramic body 26 'is dipped in a plating solution and an electric field is applied to the metallized metal layer 12 to form a nickel and gold plated metal layer on the exposed surface of the metallized metal layer 12 by electrolytic plating. The layers are sequentially layered, and finally the fired ceramic body 26 'is cut and separated along the dividing line B formed by the arrangement of the through holes 24, whereby a large number of insulating substrates 11 are manufactured at one time.

[0008]

However, according to this conventional method, the nickel-plated metal layer 16 and the gold-plated metal layer 17 are formed on the outer surface of the metallized metal layer 12 provided on the fired ceramic body 26 'by the electrolytic plating method. In the case of attachment, one of the through holes 24 is closed in the metallized metal layer 12 on the inner surface of the through hole 24 to form a concave shape.
Since the circulation of the plating solution in the inside is extremely poor, the plating metal layers 16 and 17 cannot be completely deposited, and the metallized metal layers 16 and 17 are exposed. Therefore, when the water contained in the atmosphere adheres to this exposed portion, the water comes into contact with the nickel-plated metal layer 16 and the gold-plated metal layer 17 and acts as an electrolyte. Due to the difference in the energy levels of the metals, a battery action in which an electric current flows is caused to gradually elute the nickel-plated metal layer 16 having a low energy level, which causes a short circuit between the adjacent metalized metal layers 12. It was

At the same time, when water adheres to a part of the nickel-plated metal layer 16, a crevice corrosion action occurs in the nickel-plated metal layer 16 due to the difference in oxygen concentration, and an oxide (rust) is formed on the nickel-plated metal layer 16. May cause discoloration. Further, since this oxide is conductive and has a property of being easily diffused, the metallized metal layers 12 adjacent to each other are short-circuited by the diffusion of the oxide, and as a result, the function as a semiconductor device is hindered. Induces the serious drawback of coming.

[0010]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and its object is to plate a metallized metal layer deposited on the inner surface of a recess of a ceramic body so as to completely cover the surface of the metallized metal layer. To provide an electrolytic plating method in which a metal layer is layered, and the plated metal layer is prevented from causing a battery action or a crevice corrosion effect, and can effectively prevent discoloration or elution from occurring in the plated metal layer. is there.

[0011]

According to the electrolytic plating method of the present invention, a ceramic body having a recess having an opening diameter increasing toward the outside and having a metallized metal layer deposited on the inner surface is prepared. Immerse your body in the plating solution,
After that, an electric field is applied to the metallized metal layer to deposit a plated metal layer on the outer surface of the metallized metal layer.

[0012]

EXAMPLE Next, the electrolytic plating method of the present invention will be described with reference to FIGS.
A case where the method is applied to the manufacturing method of the package for accommodating a semiconductor element shown in FIG.

First, as shown in FIGS. 1 (a) and 1 (b), a green ceramic body 1 composed of three unfired ceramic sheets (ceramic green sheets) 1a, 1b and 1c, which are a first, a second and a third. To prepare.

Each of the unfired ceramic sheets 1a, 1b, 1c
Is alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia
It is formed by adding a suitable organic solvent and a solvent to a ceramic raw material powder such as (MgO) 2 or calcia (CaO 2) and mixing them to form a slurry, which is formed into a sheet by a conventionally known doctor blade method or the like.

Further, a large number of through holes 2b, 2c are formed in the unfired ceramic sheets 1b, 1c so as to divide the respective sheets 1b, 1c into a plurality of sections, and the through holes 2b, 2c are wide. The unfired ceramic sheets 1b, 1c having the area are divided into a plurality of sections having a shape corresponding to a desired ceramic insulating substrate, and are used as a passage for routing a metal layer for a metallized lead described later.

The through holes 2b and 2c are formed in the unfired ceramic sheets 1b and 1c by a conventionally known punching method, and the through holes 2c formed in the unfired ceramic sheet 1c.
Has an opening diameter slightly larger than that of the through hole 2b formed in the unfired ceramic sheet 1b.

Further, in the first and second unfired ceramic sheets 1a and 1b, a cavity for accommodating a semiconductor element is formed in a substantially central portion of each region surrounded by a section line C formed by an array of through holes 2b and 2c. Is formed by a punching method which is well known in the art.

A metallized lead metal layer 4a is printed and applied on the second unfired ceramic sheet 1b from the upper surface to the inner surface of the through hole 2b, and the upper surface of the third unfired ceramic sheet 1c is coated. The metal layer 5 for die attachment for attaching the semiconductor element to the through hole
Metal layer for metallized leads from the inner surface to the lower surface of 2c
4b is printed and applied.

The metallized lead metal layers 4a and 4b and the die attach metal layer 5 are formed by adding a suitable organic solvent or solvent to a refractory metal powder such as tungsten (W), molybdenum (Mo), or manganese (Mn). Then, the paste-like metal paste is printed and applied to each of the unfired ceramic sheets 1b and 1c by adopting a conventionally known screen printing method.

The above three unfired ceramic sheets 1a, 1
The b and 1c are sequentially laminated by precisely aligning the center positions of the through holes 2b and 2c, and thermocompression-bonded by a hot press machine heated to about 150 ° C. to produce the raw ceramic body 1.

Next, the green ceramic body 1 is placed in a reducing atmosphere.
(In H ₂ -N ₂ gas) at a temperature of approximately 1400 to 1600 ° C. to sinter the raw ceramic body 1, the metallized lead metal layers 4 a and 4 b, and the die attach metal layer 5 into a single body, As shown in 1 (c), a fired ceramic having a metallized metal layer 4 ′ and a die attach metal layer 5 ′ that are led to the outside through the inner surface of a through hole (recess) 2 ′ that is closed on one side. Get body 1 '.

In the fired ceramic body 1 ', the opening diameter of the through hole 2c provided in the unfired ceramic sheet 1c is slightly larger than the opening diameter of the through hole 2b provided in the unfired ceramic sheet 1b. Opening diameter of recess 2'is outside (bottom surface)
Is getting bigger towards.

Then, as shown in FIG. 1 (c), plated metal layers 6 and 7 made of nickel (Ni) and gold (Au) are formed on the outer surfaces of the metallized metal layer 4'and the die attach metal layer 5 '. Layer in order. This plated metal layer 6, 7 is a metallized metal layer
4'and the die attach metal layer 5'have the function of preventing oxidative corrosion, and when the metallized metal layer 4'and the external electric circuit board are brazed, or the die attach metal layer 5'and the semiconductor element are brazed. When applying, metallized metal layer
4 ′ and the die attach metal layer 5 ′ and the brazing material are improved in wettability to increase the bonding strength.

Metallized metal layer 4'provided on the fired ceramic body 1'and plated metal layer on the die attach metal layer 5 '
As shown in Fig. 2, the layers 6 and 7 were deposited by immersing the fired ceramic body 1'in a plating solution (nickel plating solution or gold plating solution) 8 and applying an electric field to the metallized metal layer 4'and the die attach metal layer 5 '. It is performed by applying. still,
In this case, since the opening diameter of the recess 2'formed in the fired ceramic body 1'becomes larger toward the outside (lower surface), circulation of the plating liquid 8 in the recess 2'is improved, and as a result, the ceramic body is It is possible to deposit the plated metal layers 6 and 7 on the surface of the metallized metal layer 4'applied to the inner surface of the recess 2'of 1'with a uniform thickness and so as to completely cover the metallized metal layer 4 '. Becomes

The plating solution 8 is, for example, in the case of a nickel plating solution, the composition of the solution 8 is nickel sulfate 180 to 300 g / liter, nickel chloride 30 to 60 g / liter, and boron 20 to 60 g / liter, The calcined ceramic body 1'is dipped in the liquid and an electric field is applied to the metallized metal layer 4'and the die attach metal layer 5'for a current density of 2 to 4 A / dm ² for about 3 minutes. A nickel plating layer 6 is deposited on the surfaces of 4'and the die attach metal layer 5 '.

Finally, the fired ceramic body 1'is cut along the division line C by the arrangement of the through holes shown in FIG. 1 (c) to separate it into individual ceramic insulating substrates, thereby producing a semiconductor device as a product. The storage package is completed.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention.

[0028]

According to the electrolytic plating method of the present invention, since the opening diameter of the recess provided in the ceramic body is increased toward the outside, the metallized metal layer deposited on the inner surface of the recess is plated by the electrolytic plating method. When the layer is deposited, the circulation of the plating solution into the recess is improved, and the plating metal layer can be deposited on the surface of the metallized metal layer so as to completely cover the metallized metal layer. It is possible to prevent discoloration and elution from occurring in the plated metal layer due to the battery action and the crevice corrosion action.

[Brief description of drawings]

1 (a), (b) and (c) show an embodiment of a method for manufacturing a semiconductor device housing package using the electrolytic plating method of the present invention, and (a) shows firing of a semiconductor device housing package. Partial exploded perspective view showing the previous state, (b) is (a)
Is a partial cross-sectional view showing a laminated state, and (c) is a partial cross-sectional view showing a state after firing (b).

FIG. 2 is a schematic view of a plating apparatus for depositing a plating metal layer on the surfaces of the metallized metal layer and the die attach metal layer provided on the ceramic body shown in FIG. 1 (c).

FIG. 3 is a cross-sectional view of a conventional semiconductor element housing package.

FIG. 4 is a partial cross-sectional view for explaining the method of manufacturing the semiconductor element housing package shown in FIG.

[Explanation of symbols]

 1 '... Ceramic body 2' ... Recessed portion 4 '... Metallized metal layer 5' ... Die attach metal layer 6 ... Nickel plated metal layer 7 ... Gold plated metal layer 8 ... ..Plating liquid

Claims (1)

[Claims] 1. A ceramic body having a recess having an opening diameter increasing toward the outside and having a metallized metal layer deposited on the inner surface is prepared, and then the ceramic body is immersed in a plating solution, and thereafter, An electroplating method comprising applying an electric field to the metallized metal layer to deposit a plated metal layer on the outer surface of the metallized metal layer.