JPS60198760A - Soldering method - Google Patents

Abstract

PURPOSE:To enable treatment at low temperatures in a neutral atmosphere by a method wherein a film of a metal of the group VIa is formed at the part of soldering on a ceramic substrate, and a film of a metal of the group VIII is formed thereon; then, an input-output electrical connection pin of solder is soldered thereon. CONSTITUTION:A chromium film 33 of 300Angstrom -1,000Angstrom thickness is formed on the surface of a multilayer ceramic substrate 31. A layer 34 of palladium a metal of the group VIII is successively formed from above the chromium film 33. The ceramic substrate having a metallic pad is placed on a plurality of the input-output electrical connection pins 36 made of kovar or 4.2 alloy to which an alloy 35 having a weight ratio of Au 80% and Sn 20% has been installed respectively to approx. 1-3mg, and is thus bonded on the layer of palladium a metal of the group VIII. The surface of the metallic pin 36 is coated with an Au coat layer 37 formed by plating and the like.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The invention relates to a method for bonding input/output electrical connection pins on a package substrate, more specifically, to a method for bonding connection pins of a multilayer ceramic substrate to the substrate. (Prior art) The requirements for package substrates at the mounting level are becoming increasingly strict due to the recent miniaturization, high speed, and high performance of recent combinator systems, etc. . Specifically, there are demands for increasing wiring density and miniaturizing signal line widths on package substrates, lowering the resistance value of signal line conductors, and lowering the dielectric constant of insulating materials. A new package substrate technology has been developed. For example, multilayer ceramic substrates using alumina green sheets, low-temperature sintered multilayer ceramic substrates that can be sintered at about 900℃ using glass ceramic green sheets, and low-temperature sintered ceramic substrates that can use silver-palladium conductors, and thin films such as Hesbatter or vapor deposition on ceramic substrates. There are package substrates that use advanced technology, and even package substrates that combine organic insulating materials (polyimide, etc.) with thin film conductors.□On these high-density, miniaturized mounting substrates, there are many ultra-LSI chips. Therefore, the number of input/output terminals for electrical connection with the outside of the board becomes extremely large. Therefore, a technology was developed to form input/output terminals in the form of pins on the back side of the multilayer board. ◎ As a conventional technique, for example, a connecting pin made of Kovar or 4.2 alloy was attached to an alumina multilayer board using silver solder. The figure shows a ceramic substrate 1 and a conductor made of molybdenum or tungsten after sintering conductor pads made of molybdenum or tungsten formed on an alumina green sheet and conductors in through holes at a temperature of 1500°C or higher in a reducing atmosphere. A nickel layer 3 is formed on this conductor pad portion by plating, and then a connecting pin 5 made of copal or 4.270 mm is attached to a silver filter 54. The composition of silver solder is generally Ag6
0mo/fb-Cu40rrDl! *The eutectic alloy used has a melting point of 779℃, and the processing temperature for brazing is q8.
(at about 10℃), the zero-order substrate is processed in a hydrogen reducing atmosphere to prevent oxidation of conductors such as sorybdenum. !
? The attached connection pins and conductors are gold-plated to prevent deterioration. Figure 2 shows a board with a connecting bottle on which a gold layer 6 is formed.The brazing method requires a high processing temperature, and it is difficult to heat fine thin film patterns formed on the board to this temperature. However, on the other hand, even when forming fine thin film patterns such as signal lines after attaching the vials to the substrate, the accuracy of forming various patterns on the substrate with vials is poor and the workability is also reduced. The same applies to packaging technology in which patterns are formed on multilayer ceramic substrates using organic insulating films (polyimide, etc.). Furthermore, brazing involves the process of gold-plating the connection pins and conductor pads, resulting in poor workability.Next, in order to lower the processing temperature, Au-8n is used as a brazing material.
Or Au-8i, Au-8n-Pd, Au-a
n-Ag, etc. have been studied, and a specific example is shown in FIGS. 3 and 4. In FIG. □Next, a gold coating 14 is formed using gold paste on the nickel coating, and a gold/nickel solid solution is formed by heat treatment.Next, gold plating 17 is applied. The connection bottle 16 that has been
It is multi-bonded to the U-8N brazing filler metal 15. In this method, the gold-nickel solid solution is formed under hydrogen reduction at a temperature of about 700°C. A nickel film '23 is formed on the nickel film, and a gold film 24 for a barrier is formed on the nickel film. The gold coating is coated with a group 1 metal layer 25 that serves as a source of 8N gettering metal, and then a connection vial 27 plated with gold 28 is coated with an Au-8111 brazing material 2.
6. ζ.

In both of these methods, a gold layer must be formed as an intermediate layer, which is disadvantageous in terms of cost.

In addition, molybdenum pads must be formed in advance on the pads to which the connecting bottles are attached, which is disadvantageous in terms of process and cost.Moreover, even during heat treatment such as brazing, molybdenum oxidation is prevented. In addition, additives such as glass frit must be included in the molybdenum paste to ensure good adhesion between the molybdenum pad and the ceramic substrate, which increases conductor resistance. Yes (Objective of the invention) The object of the present invention is to eliminate such conventional drawbacks,
Unlike the conventional method using silver brazing material, heat treatment can be performed at low temperatures (below 400°C) and in a neutral atmosphere.

In addition, unlike other conventional methods, the gold coating for barriers is not applied, and the pin attachment has a very simple structure without forming molybdenum pads, which is advantageous in terms of workability and cost. It is an object of the present invention to provide a method for brazing with sufficient pin bond strength.

(Structure of the Invention) That is, the present invention includes a step of forming a metal film of Group Ⅰa of the periodic table on a portion to be brazed on a ceramic substrate, and a step of forming a metal film of Group 1 of the periodic table on the chromium film. a step of forming;
Brazing is a method characterized by comprising the step of brazing input/output electrical connection pins onto the Group ① metal layer using a brazing filler metal. Detailed examples are shown in Figure 5 based on
FIG. 8 is a diagram showing the brazing method of the present invention. FIG. 9 is a schematic diagram of a ceramic substrate with pins produced in an example. As shown in FIG. 5, a multilayer ceramic substrate 31
For brazing, a thin metal plate is formed by etching or other means on the ceramic surface of the multilayer ceramic board 31, which is formed by overlapping a mask 32 with an open area.The multilayer ceramic board 31 is made of an alumina green sheet and printed with molybdenum or tungsten as a conductor. It may be sintered in a hydrogen reducing atmosphere at 1500°C or higher after laminated pressing, or it may be a glass made from lead borosinate crystallized glass and alumina.
Using Gutsuku Green Sheet, gold, silver and silver are used as conductors.
So-called low-temperature sintered multilayer ceramic substrates printed with palladium, gold-platinum, silver-platinum, etc. and sintered in an oxidizing atmosphere at 1000°C or less after laminated pressing may also be used. The latter substrate using barium was used.

Next, a film was formed from a Ma group metal.
Forming the PM film 33 with a thickness of to form.

The palladium layer was formed by spackling similar to the process used to form thin films.
The gas was introduced to about 10 torr. 8th
The figure shows a cross-sectional view when the mask is removed after forming a chromium thin film and a Group Ⅰ metal film. As can be seen from FIG. 8, this method is characterized in that a chromium film is formed directly on the surface of the ceramic substrate, which is one of the features that differs greatly from other methods.

The thus obtained ceramic substrate having a metal pad portion of 9.5 mm was then used as an alloy brazing material of 80% gold and 20% tin.
A plurality of input/output electrical connection bins 36 made of materials such as Kovar or 4.2 alloy, each with approximately 1 to 3 mg of
Figure 9 shows a schematic diagram of a multilayer ceramic board with connection pins attached by the above method. The surface of the bottle 360 is coated with a gold coating layer 37 formed by plating or the like. ◎ Brazing is performed and the processing temperature is such that the melting point of the alloy brazing material with a weight ratio of 80% gold and 20% tin is 280. ℃, a layer of Group 0 metal, such as palladium, formed in a temperature range of 300℃ to 450℃ for 10 to 30 minutes will cause gettering of tin in the gold-tin brazing material, and the appearance of gold with respect to tin will increase. Therefore, it is effective to increase the melting point of the brazed joint after cooling or condensation of the brazing filler metal. 0 Also, with respect to the gold coating layer placed on the connecting bottle, brazing may be difficult if the gold coating layer partially melts together with the gold-tin brazing material during processing. The adhesion strength between the input/output electrical connection ins and the multilayer ceramic substrate, which are brazed using the 0-wire method in which the proportion of gold increases and the melting point of the bonded part is increased to achieve the same effect, is 4. It shows OKf/- or more and shows sufficient strength as an input/output bin of a mounting board. At extremely low temperatures below ℃,
Moreover, it can be carried out in a neutral atmosphere, and there is no need to form a thick metal (molybdenum, tungsten, gold, silver; silver-palladium, etc.) layer for the via pad on the surface of the ceramic substrate, and it is not necessary to form a layer for the barrier pad. It has now become possible to obtain a bottled substrate with a simple structure that does not require any gold coating and has sufficient adhesive strength. Furthermore, since the method of the present invention does not involve a wet process such as etching when forming the metal layer of the bottle pad, it does not have any adverse effects on the ceramic and can provide a highly reliable substrate with a bottle. It is also advantageous in terms of cost, and it has become possible to use pins that are strong enough to withstand subsequent thermal cycles. Via group metals can be used, and film forming means such as vapor deposition, plating, screen printing, etc. can be used as appropriate in addition to loss battering, which can use metals of group 1 other than palladium.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams showing conventional ceramic substrates with pins, Figures 5 to 8 are diagrams showing the method of the present invention, and Figure 9 is a diagram showing the method of the present invention. FIG. 2 is a schematic diagram of a pin-equipped substrate manufactured by the method of the invention. In the figure, 1, 11, 21, 31...ceramic substrate, 2. 12. 22...Thick film conductor pad layer, 3゜13, 23...Nickel layer, 4...Silver solder, 5,1
6゜27.36・;・Metal pin, 6,17,28,37
... Gold coating layer, 14... Gold coating, 15, 26.35
...Gold-tin layer 9.24...Gold coating, 25...Palladium layer, 32...Mask, 33...Chromium film, 3
4... Palladium membrane. Figure 1 Helmet Figure 2 Man Figure 3 Figure 4 Figure 5 Figure 2

Claims (2)

[Claims] (1) A step of brazing metal connection pins onto a ceramic substrate using a brazing material, and forming a metal film of group Ma of the periodic table on the part to be brazed on the upper two-layer substrate. , comprising a step of forming a metal film of Group 1 of the periodic table on the metal film of Group Ma, and a step of brazing a multi-connection pin with a brazing material onto the metal layer of Group Ⅰ. Brazing method 0 is characterized by (2) Claim 1: The brazing material is a gold-tin brazing material.
Brazing described in section 0 is method 0.