JPH0231502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pin attachment structure and attachment method on a package substrate, and more specifically, a connection pin attachment structure for a multilayer ceramic substrate and a connection pin to the substrate. It relates to a joining means for

(Prior art) Recent computer systems have become more compact and dense,
The requirements for package substrates at the mounting level are becoming stricter in order to achieve higher speeds and higher performance. Specifically, there are demands for higher wiring density on package boards, smaller signal line widths, lower resistance values of signal line conductors, and lower dielectric constants of insulating materials. Package board technology has been developed. For example, multilayer ceramic substrates using alumina green sheets, glass ceramic green sheets can be sintered at around 900℃, and Au and
There are multilayer ceramic substrates that can use Ag-Pd conductors, package substrates that use thin film techniques such as sputtering and vapor deposition on ceramic substrates, and package substrates that use organic insulating materials (polyimide, etc.) in combination with thin film conductors. In this way, densification,
A large number of VLSI chips will be mounted on a miniaturized mounting board, and as a result, the number of I/O terminals for electrical connection with the outside of the board will become extremely large. Therefore, a technique has been developed in which I/O terminals are formed using pins on the back surface of a multilayer substrate.

As a conventional technique for attaching connection pins to this multilayer ceramic substrate, for example, connection pins made of a material such as Kovar or 4.2 alloy were attached to an alumina multilayer substrate using silver solder. Figure 1 is a cross-sectional view for explaining the conventional method, in which conductor pads made of molybdenum or tungsten formed on an alumina green sheet and conductors in through holes are sintered in an annular atmosphere at a temperature of 1500°C or higher. The resulting ceramic substrate 1 and conductor 2, such as molybdenum or tungsten, are shown. A nickel layer 3 is formed on this conductor pad portion by plating, and then a connecting pin 5 of Kovar or 4.2 alloy is attached using silver solder 4. The composition of silver solder is generally a eutectic alloy of 60 mol% Ag - 40 mol% Cu, with a melting point of 779°C and a brazing temperature of about 810°C. It is carried out in a reducing atmosphere. The connection pins and conductors attached to the board are then gold-plated to prevent deterioration. FIG. 2 shows a cross-sectional view of a substrate with connection pins on which a gold layer 6 is formed. This method requires a high brazing temperature, and it is difficult to heat fine thin film patterns formed on the substrate to this temperature.On the other hand, pins are attached to the substrate in advance and then fine thin film patterns such as signal lines are formed. Even in this case, the accuracy when forming various patterns on the pin-equipped substrate becomes low, resulting in poor workability. The same applies to packaging technology in which a pattern is formed on a multilayer ceramic substrate using an organic insulating film (polyimide or the like). Furthermore, it involves a step of gold plating the connection pins and conductor pads after brazing, resulting in poor workability.

Next, in order to lower the processing temperature, Au was used as a brazing material.
−Sn or Au−Si, Au−Sn−Pd, Au−Sn−Ag
etc. were considered. A specific example is shown in FIGS. 3 and 4. In Fig. 3, the ceramic substrate 1
A molybdenum layer 12 is attached to the surface of the substrate 1, and a nickel coating 13 is formed on the molybdenum layer by a plating method or the like. Next, a gold coating 14 is formed on the nickel coating using gold paste, and a gold/nickel solid solution is formed by heat treatment. Subsequently, connection pins 16 coated with gold plating 17 are connected using Au--Sn brazing material 15. In this method, the gold-nickel solid solution is formed at a temperature of approximately 700°C under hydrogen reduction. Further, in FIG. 4, a molybdenum layer 22 is attached to the surface of a ceramic substrate 21, a nickel film 23 is formed on the molybdenum layer, and a gold film 24 for a barrier is formed on the nickel film. On the gold coating, Sn
After being coated with a group metal layer 25 serving as a source of gettering metal, a connecting pin 27 plated with gold 28 is bonded by an Au--Sn brazing material 26. In all of these methods, metal must be formed as an intermediate layer, which is disadvantageous in terms of cost. In addition, a molybdenum pad must be formed in advance on the pad where the connecting pin is attached, which is disadvantageous in terms of process and cost.Furthermore, during heat treatment such as brazing, hydrogen is used to prevent molybdenum from oxidizing. It had to be done in a reducing atmosphere. Furthermore, in order to provide good adhesion between the molybdenum pad and the ceramic substrate, additives such as glass frit must be included in the molybdenum paste, resulting in the problem of increased conductor resistance.

(Object of the invention) The object of the present invention is to eliminate such conventional drawbacks, to enable heat treatment at a lower temperature (400°C or less) and in a neutral atmosphere than the conventional method using silver brazing material, and to be able to perform heat treatment in a neutral atmosphere. To provide a substrate with pins and a method for manufacturing the same, which does not require a gold coating for a barrier as shown in conventional methods, has a very simple structure, is advantageous in terms of workability and cost, and has sufficient pin bonding strength. There is a particular thing.

(Structure of the Invention) That is, the present invention includes a chromium metal layer formed directly on a substrate, a palladium metal layer formed on the chromium metal layer, and a metal pin formed on the palladium metal layer via a brazing material. A step of forming a chromium metal film on a substrate with pins and a substrate, a step of forming a palladium metal film on the chromium metal film, and a step of laminating a dry film, exposing it, and developing it. A method of manufacturing a pin-equipped substrate is characterized by comprising the steps of etching the palladium metal layer and the chromium metal layer, and brazing the connecting pins onto the palladium metal layer using a brazing material.

(Examples) The present invention will be described in detail below based on Examples.

5 to 11 are diagrams showing the manufacturing method of the present invention, and FIG. 12 is a schematic diagram of a substrate with pins of the present invention produced in an example. As shown in FIG. 5, a thin chromium film 32 is coated on the ceramic surface of a multilayer ceramic substrate 31. As shown in FIG. The multilayer ceramic substrate 31 is made of an alumina green sheet printed with molybdenum or tungsten as a conductor, laminated pressed and then sintered in a hydrogen reducing atmosphere at 1500°C or higher, or a glass ceramic green sheet with gold, silver-palladium, or gold printed as a conductor. -Platinum,
A so-called low-temperature sintered ceramic substrate, which is printed with silver-platinum, silver, etc., laminated and pressed, and then sintered in an oxidizing atmosphere at 1000° C. or lower, can be used. In this example, a low-temperature sintered ceramic substrate printed with the latter silver-palladium was used. On the other hand, the chromium thin film was formed by sputtering to a thickness of 500 Å to 2000 Å. Next, a palladium layer 33, which is a metal of group 3 of the periodic table shown in FIG. 6, is formed on the chromium thin film shown in FIG. The palladium layer was formed to a thickness of 500 to 2000 Å by sputtering, similar to the formation of the chromium thin film.
Sputtering was carried out at a temperature of 10 ^-5 torr or less, and then Ar gas was introduced at a temperature of about 10 ^-2 torr. A dry film (manufactured by Dupont, trade name Riston) 34 was applied to the ceramic substrate on which the thin film was formed as shown in Fig. 6. After laminating as shown above, a pin pad pattern mask is placed on top of the other, exposed to ultraviolet light, developed, and the parts other than the pin pad pattern are washed away. Figure 8 shows exposure,
Polymerized resist layer 3 on the pin pad portion remaining after development
5 is shown. Next is the palladium metal etching step, as shown in FIG. 9, where the palladium layer is removed by etching using an FeCl ₃ -based etchant, leaving a pad portion. Figure 10 shows the chromium layer removed by etching, but the etchant used when etching the chromium is
An aqueous solution containing AlCl ₃ and HCl was used. FIG. 11 shows a structure in which a chromium layer and a palladium layer are formed on a ceramic substrate from which a dry film layer has been removed. The dry film layer was removed by burning through heat treatment. The ceramic substrate with the metal pad portion thus obtained was made of Au80.
An alloy brazing filler material 36 having a weight ratio of %Sn20% is placed on a number of Kovar or 4.2 alloy connecting pins 37 with approximately 1 to 3 mg of each pin attached, and bonded to a layer of palladium, which is a group metal. FIG. 12 shows a schematic diagram of a board with pins attached by the above method, and the surface of the connection pin 37 is coated with metal formed by plating or the like. The processing temperature for brazing is 80% Au.
The melting point of the alloy brazing filler metal with a weight ratio of 20% Sn is 280°C, and the test was carried out at a temperature range of 300°C to 450°C for 10 to 30 minutes. The palladium layer causes gettering of Sn in the Au-Sn filler metal, increasing the apparent ratio of Au to Sn and thus increasing the melting point of the brazed joint after cooling or condensation of the filler metal. It has the effect of This is effective in cases where there is a step of applying a thermal cycle after attaching the pin. Also, when the metal applied to the connecting pin is brazed, the metal melts together with the Au-Sn brazing material, increasing the proportion of Au in the Au-Sn brazing material and raising the melting point, producing the same effect. . The adhesion strength of the brazed connection pins to the ceramic substrate was 4.0 Kg/mm ² or more, indicating sufficient strength as I/O pins on a mounting board.

(Effects of the Invention) As described above, by adopting the structure and manufacturing method of the pin-equipped substrate of the present invention, the brazing process can be easily performed.
It can be carried out in a neutral atmosphere at a low temperature of 400℃ or less, and there is no need to previously form a thick metal layer (molybdenum, tungsten, gold, gold-platinum, etc.) for pin pads on the surface of the ceramic substrate, and there is no need to form a barrier layer. It has now become possible to obtain a pin-equipped substrate with a simple structure that does not require any additional gold coating and has sufficient adhesive strength. Further, the present invention is advantageous in terms of workability and cost, and it has become possible to obtain a pin-equipped substrate that is resistant to thermal cycles after pin-setting.

In addition to sputtering, metal film forming methods such as vapor deposition, plating, and screen printing can be used as appropriate.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams showing the structure of a conventional ceramic substrate with pins, Figures 5 to 11 are diagrams showing the manufacturing process of the present invention, and Figure 12 is a diagram showing the manufacturing process of the present invention. FIG. 2 is a schematic diagram of a pin-equipped substrate manufactured by the manufacturing method. In the figure, 1, 11, 21, 31...ceramic substrate, 2, 12, 22...thick film conductor pad layer,
3, 13, 23...nickel layer, 4...silver wax,
5, 16, 27, 37... Connection pin, 6... Gold layer, 14... Gold coating, 15, 26, 36... Au
-Sn wax, 17, 28, 38...gold plating layer,
24... Gold coating, 25... Palladium layer, 32...
...Chromium coating, 33... Palladium coating, 34...
...Dry film, 35...Polymerized resist layer.

Claims (1)

[Claims] 1. A structure in which a chromium metal is formed directly on a substrate, a palladium metal layer is formed on the chromium metal layer, and a metal pin is formed on the palladium metal layer via a brazing material. A board with pins. 2. Forming a chromium metal film on the substrate;
A step of forming a palladium metal film on the chromium metal film, a step of laminating the dry film, exposing and developing it, a step of etching the palladium metal layer and the chromium metal layer, and a step of attaching the connecting pin onto the palladium metal layer using a brazing material. 1. A method for manufacturing a board with pins, the method comprising the step of brazing.