JPH01143394A - Ceramic package with lead - Google Patents

Abstract

PURPOSE:To obtain a ceramic package with leads having preferable adhesive properties of a plating layer with a ceramic substrate by providing front layer ceramics having an anchoring effect. CONSTITUTION:The inner layer 2 of a ceramic substrate is formed by adding and mixing the ceramic material of a stock and a crystal bonding material and further organic binder to form a green sheet, opening holes 4 at predetermined positions and simultaneously punching it in working size. Paste of W, Mo, etc., is filled in the holes 4, the sheet is printed with paste 5a, thereby forming a circuit. Then, a lower layer 3 is similarly formed, pastes 5b, 5c are printed on the sheet thereby to form a circuit. An upper layer 1 is eventually formed of the similar material, surface layer ceramics 6 are formed on the sheet, and holes 4 are opened at predetermined positions. The upper layer 1, the inner layer 2 and the lower layer 3 are laminated under pressure by a press, and baked, thereby forming a package substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic package with leads that establishes conduction between wiring patterns via via holes.

(Prior Art) Conventionally, thick film methods, thin film methods, plating methods, and the like are known as methods for producing ceramic packages with leads that establish conduction between wiring patterns via via holes.

The thick film method, the manufacturing process of which is shown in FIG. 4(a), is characterized by a simple process. The thin film method, whose manufacturing process is shown in FIG. 4(b), and the plating method, whose manufacturing process is shown in FIG. 4(C), have the characteristics of being able to narrow the wiring pattern width and achieve high-density wiring. .

(Problems to be Solved by the Invention) However, in the above-mentioned thick film method, the wiring pattern width on the substrate surface is at the limit of 100 μm with stable quality, and is not suitable for high-density wiring. There were drawbacks.

In addition, in thin film methods, when sputtering or vapor deposition is used, it is sensitive to irregularities, roughness, and defects on the substrate surface.
There was a drawback that the yield rate decreased.

Furthermore, there was also the drawback that the device cost and manufacturing cost were high.

Furthermore, when a conductive paste is used in the via hole in the plating method, when etching with an alkali metal compound, the conductive material inside the via hole is exposed to the etching agent, which has the disadvantage of corroding and causing poor continuity. there were. In addition, after etching the substrate with holes in advance,
When filled with conductive paste and fired, only the paste shrinks during firing, creating voids.

Furthermore, when applying a plating layer to via holes using a plating method, as the density of the via holes increases, the diameter decreases, so electroless plating must be performed in order to make the via holes conductive by plating. This has the drawback that air remains in the holes, which prevents the plating from being completely adhered to, resulting in void defects, which can easily lead to accidents where electrical continuity is lost.

An object of the present invention is to eliminate the above-mentioned problems and provide a ceramic package with leads that has high reliability in via holes and good adhesion between the plating layer forming the electrode pattern and the ceramic substrate. .

(Means for Solving the Problems) The leaded ceramic package of the present invention has a ceramic substrate surface having an electroless plating layer forming a wiring layer on a surface ceramic in which holes having an anchor effect are formed, a back surface and The feature is that electrical conduction is established between the pin and the pin via a via hole.

(Function) In the above-mentioned configuration, due to the action of the surface ceramic layer formed on the ceramic substrate and consisting of holes having an anchor effect, good adhesion between the electroless plating layer forming the wiring layer provided thereon and the ceramic substrate is achieved. A leaded ceramic package can be obtained.

Furthermore, it is preferable to form the via holes by printing, since this results in fewer voids and higher reliability than via holes formed by plating.

(Example) A specific example of the leaded ceramic package and the manufacturing method thereof according to the present invention will be described with reference to FIG. 1 showing a ceramic package and FIG. 2 showing a flowchart of the manufacturing method.

First, the basic model will be explained with reference to FIG.

Although FIG. 1 explains the case where the ceramic substrate consists of three layers, an upper layer 1, an inner layer 2, and a lower layer 3, the number of inner layers is not limited to one layer, and may be two or more layers.

First, the inner layer 2 is a green sheet formed by mixing raw ceramic material and a glass component flux, which is an example of a crystalline binder, as well as an appropriate organic binder, plasticizer, and organic solvent, and is placed in a predetermined position. , which is punched out to the processing dimensions at the same time as the hole 4 is opened. Inside the hole 4, W, Mo.

Filled with paste such as Cu, Ag, Ag-Pd, etc., and further filled with W, Mo, Cu, etc. on the green sheet.
Ag.

5a of Ag-Pd etc. is printed to form a circuit.

Next, the lower layer 3 is a green sheet formed by mixing the raw ceramic material and a glass component flux, which is an example of a crystalline binder, as well as an appropriate organic binder, plasticizer, and organic solvent. At the same time as the hole 4 was drilled, it was punched out to the working dimensions. Inside the hole 4, W, Mo.

Filled with paste such as Cu, Ag, Ag-Pd, etc., and further filled with W, Mo, Cu, Ag on top of the green sheet.

5b and 5C of Ag-Pd etc. are printed to form a circuit. - Finally, the upper layer 1 is formed on the surface of a green sheet formed by mixing the raw ceramic material and a glass component flux, which is an example of a crystalline binder, as well as an appropriate organic binder, plasticizer, and organic solvent. In this case, a surface layer ceramic 6 is formed by applying granular ceramic by printing, using a roll coater, spraying, or the like, and punching out holes 4 at predetermined positions at the same time as punching.

The upper layer 1, the inner layer 2, and the lower layer 3 are laminated under pressure using a press or the like, and then fired to form the package substrate 7.

The package substrate 7 is subjected to electroless plating and further electroplating if necessary, and then a circuit 8 is formed on the lower layer 1 and the surface by a printing method or a photolithography method. A pin 10 is attached to the lower layer 3 by a method such as brazing.

FIGS. 3(a) to 3(d) are diagrams illustrating the method for forming the surface layer ceramic of the present invention.

A ceramic material as a raw material and a glass component flux which is an example of a crystalline binder, as well as an appropriate organic binder,
A multi-layered structure is formed by arranging granular ceramic material 9 as shown in FIG. 3(a) and providing surface ceramic 6 on a green sheet formed by adding and mixing a plasticizer and an organic solvent. do. Next, when the green sheet is sintered, the glass component of the crystalline binder in the green sheet oozes out and wets the surface of the granular ceramic material as shown in FIG. 3(b). A bonding layer 12 is formed using the glass component. After sintering, the lower end of the granular ceramic material is sintered to become denser and firmly bonded to the clean sheet through the bonding layer 12. In this way, granular protrusions are formed by these granular ceramic materials, and gaps 13 are formed between the granular protrusions, which widen toward the back when viewed from the upper surface side. As shown in FIG. 3(C), a part of the applied electroless plating layer 15 penetrates into this gap 13 and solidifies, thereby exerting a strong anchor effect.

Ceramic materials including the granular ceramic material 9 include alumina, beryllia, silicon nitride, zirconia, mullite, and the like. In addition to the glass component, the crystal binder may include a material having a lower melting point than the main component ceramic,
There are materials with large diffusion coefficients. In short, any ceramic material and crystal binder may be used as long as the ceramic material and crystal binder are used to form a ceramic having a structure in which the crystal binder serves as a sintering aid for a ceramic material containing the main component. The reason for this is that the crystal binder has a tendency to migrate significantly during firing, diffuse with a concentration gradient, and migrate to surfaces such as grain boundaries where the energy level is low, and this results in wetting the surface of the granular ceramic. be.

In explaining the basic model, the surface ceramic 6 is made of the granular ceramic material 9 arranged in one layer that does not contain the crystal binder, but even if the surface ceramic 6 contains the crystal binder. Alternatively, the granular ceramic material 19 may have two layers, three layers, etc. A drawing corresponding to FIG. 3(b) in the case of two layers is shown in FIG. 3(fi), where the same numbers indicate the same contents.

Next, conditions under which granular protrusions as described above are formed will be described in detail.

1) The total amount of the component corresponding to the crystal binder contained in the green sheet 11 and the component corresponding to the crystal binder contained in the ceramic material, including the case where the total amount of the component corresponding to the crystal binder contained in the green sheet 11 is not included at all, is Must be greater than the total amount.

The reason for this is that at least the uppermost layer particles of the surface ceramic 6 formed on the green sheet 11 are not filled with the crystal binder, and granular protrusions are formed there.

2) The green sheet 11 is densified by sintering,
It is necessary to sinter at a temperature that will bond it to a dense body.

The reason for this is that if the surface layer ceramic 6 is sintered at the temperature at which it is fired, the green sheet 11 will not be sintered densely but will be in a brittle state.

3) The shape of the granular ceramic material needs to be spherical or close to spherical, such as an ellipse.

The reason for this is to form a gap 13 that widens toward the back when viewed from the front side.

The granular gaps 13 of the granular ceramic material can be controlled by an oxidatively combustible gap-forming material such as graphite or carbon particles having a size that forms a desired gap between the granular ceramic materials.

Next, in order to form a multilayer structure of the green sheet 11 and the surface ceramic 6, the most suitable method is selected and used from among the following methods (1) to (4).

■ A paste slurry prepared by mixing a granular ceramic material with an organic binder, an organic solvent, a plasticizer, a gap forming material, etc. and adjusting the viscosity to 2000 cps is coated on both sides of the strip-shaped green sheet 11 using a reverse coater. A means of spreading.

■ Similar to ■, granular ceramic material is mixed with an organic binder, an organic solvent, a plasticizer, a gap forming material, etc.
00C1] A means for applying a slurry adjusted to a viscosity of S to one or both sides of the green sheet 11 by a spray coating method.

(2) A means for transferring slurry, which has been previously applied to transfer paper, onto one or both sides of the green sheet 11.

■ Means for printing slurry on one or both sides of the green sheet 11 by screen printing.

It should be noted that the multi-layer structure formed by the above-mentioned means will not be welded to each other even if the multi-layer structure is stacked in multiple stages and fired at the same time.

The reason for this is that the purity of the ceramic in the surface layer is high.
This is to prevent welding during firing.

Next, an actual example will be explained.

Example 1 90% by weight of alumina powder with an average particle size of 2 μm and low soda content, 10% by weight of MgO, Cab, 5in2 powder, butyral resin as an organic binder, plasticizer DOP, and organic solvents toluene and butanol were mixed in an alumina ball mill. They were mixed and adjusted to a slurry with a viscosity of about 5000 cps.

This slurry was made into green tape using a tape forming machine.

Predetermined holes were punched out in the green tape using a press machine, and the holes were filled with a paste using dungsten powder with an average particle size of 1 μm, and then predetermined conductor wiring was screen printed with a paste using tungsten powder with the same particle size. The top layer of green tape is Mg050% by weight with an average particle size of 1 μm.
After adjusting the viscosity to 200 cps, a paste using 50% by weight of alumina powder with an average particle size of 2.0 μm was applied as a surface ceramic layer by spraying, and after drying, predetermined holes were similarly punched out and filled with conductive paste. I did it. Tapes with predetermined wiring were laminated and integrated at a temperature of 150°C and a pressure of 20 kg/cm', then cut into predetermined dimensions and fired in a hydrogen atmosphere at about 1600°C. After applying 1 μm of N1 electroless plating to the front surface of the fired substrate, photoresist was applied to the entire surface, a circuit pattern was formed on the surface, and etching was performed with a ferric chloride aqueous solution to form wiring with a line width of 50 μm. In addition, in the same process, a pad of 1.8 diameter for attaching a lead pin was formed on the back surface. A Kovar pin was attached onto this pad using eutectic silver solder (Ag-Cu) in a hydrogen atmosphere at about 850°C.

After assembling the pins, 2 μm of electroless nickel plating was applied, followed by 2 μm of gold cyanide electroless plating to create a plug-in package.

The pattern on the package surface did not peel off when tested for adhesion with Scotch tape.

Also, the tensile strength of the pin attached to the back of the package is 3. It was OK.

Example 2 Kaolin with an average particle size of 4 μm and silica with an average particle size of 2 μm were mixed with the binder, plasticizer, and solvent of Example 1 to prepare a slurry, and then a predetermined green sheet was prepared.

The same punching as in Example 1 was performed, the holes were filled with a paste using molybdenum powder with an average particle size of 1.5 μm and manganese powder with an average particle size of 2 μm, and conductor wiring was printed. The top layer of green tape is zirconia powder with an average particle size of 0.4 μm.
A paste containing 0% by weight was applied as a surface ceramic layer using a reverse coater method. After drying, the punched holes were filled in the same manner as in Example 1.

The tape with the specified wiring is heated at a temperature of 150°C and a pressure of 40°C.
After laminating at a weight of kg/cm2 and making it into a single piece, it was cut into a predetermined size and fired in a hydrogen atmosphere at about 1350°C. After applying 1 μm of electroless copper plating to the entire surface of the fired body, electroplating of copper sulfate to 10 μm and electroplating of nickel to 2 μm was performed, and photoresist etching was carried out in the same manner as in Example 1, leaving a predetermined conductor. . The same brazing nickel/gold plating as in Example 1 was applied to this board to produce a plug-in package.

The pattern on the package surface did not peel off when tested for adhesion with Scotch tape.

The tensile strength of the pin attached to the back of the package was 3.5 kg.

The present invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, although the case where the surface ceramic 6 is applied to the surface of the upper layer 1 has been described, it can also be applied to the surfaces of both the upper layer 1 and the lower layer 30. moreover,
The surface ceramic 6 is coated on a clean sheet and then punched out to the processing dimensions at the same time as the holes 4 are punched at predetermined positions. After punching, a surface layer ceramic 6 may be applied. In addition, upper layer 1,
After the three layers of the inner layer 2 and the lower layer 3 are laminated, the surface ceramic layer 6 may be applied and fired.

(Effects of the Invention) As is clear from the above detailed explanation, according to the leaded ceramic package of the present invention, by providing the surface ceramic having an anchor effect, the electroless plating layer forming the wiring layer and the ceramic substrate Since these are firmly adhered to form an electrode pattern, it is possible to obtain a leaded ceramic package with good adhesion between the plating layer and the ceramic substrate.

In addition, in the preferred embodiment, the surface ceramic can be fired at the same time as the ceramic substrate, which simplifies the process, and since the via holes are formed by printing, they are more reliable than through holes formed by plating. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the leaded ceramic package of the present invention, Fig. 2 is a flowchart of the manufacturing process of the leaded ceramic package of the present invention, and Fig. 3 (a) to (d) are respectively surface layer ceramics. Figures 4(a) to 4(c) are flowcharts showing the manufacturing process of a conventional leaded ceramic package. 1... Upper layer 2... Inner layer 3... Lower layer 4... Holes 5a, 5b, 5cm...
Paste 6... Surface ceramic 7... Package board meter... Circuit 9... Granular ceramic material 10... Pin 11... Green sheet 12... Bonding layer 13... Gap 15.
・・Electroless plating layer

Claims (2)

[Claims] 1. A ceramic package with leads, characterized in that conduction is established between the surface of a ceramic substrate, which has an electroless plating layer forming a wiring layer, and the back surface and pins via via holes on a ceramic surface layer in which holes having an anchor effect are formed. . 2. The leaded ceramic package according to claim 1, wherein the surface layer ceramic and the conductive paste in the via hole are fired at the same time.