JPS60198761A - Soldering method - Google Patents

Abstract

PURPOSE:To unnecessitate metallic films for barrier by enabling soldering treatment at low temperatures in a neutral atmosphere by a method wherein a titanium film is formed at the part of soldering on a ceramic substrate. CONSTITUTION:A mask 32 made of a metallic thin plate and having an aperture at the part of soldering is superposed on the surface of a multilayer ceramic substrate 31, and a titanium film 33 is formed from above by sputtering. Next, a layer 34 of palladium a metal of the group VIII in the periodic law table is formed thereon by sputtering; thereafter, the mask 32 is removed. An alloy solder 35 having a weight ratio of Au 80% and Sn 20% is placed on the palladium layer 34, and an input-output electrical connection pin 36 coated with an Au coat layer 37 by plating and the like is heat-treated for 10-30min at a temperature of 300-450 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for bonding input/output electrical connection pins on a package substrate, and more specifically, to a method for bonding connection pins of a multilayer ceramic substrate to the substrate. (Prior art) With the recent trend towards higher density, higher speed, and higher performance in computer systems, the requirements for package substrates at the mounting level are becoming increasingly strict. . 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 around 900°C using glass ceramic green sheets, and can use gold and silver-palladium conductors, and thin film techniques such as Hess Batter deposition on ceramic substrates. There are package substrates using organic insulating materials (polyimide, etc.) in combination with thin film conductors, etc.
Ultra-L
I hope that a large number of 8I chips will be implemented.
The number of input/output terminals that are electrically connected to the outside of the board is becoming extremely large. Therefore, a technology has been developed in which input/output terminals are formed with pins on the back of the multilayer board. * Connected to this multilayer ceramic 5-socket board. Conventional techniques for attaching bottles include, for example, attaching connecting bottles made of materials such as Kovar or 4.2-Api to an alumina multilayer board using silver solder. ◎Figure 1 explains the conventional method. (This is a diagram for the purpose of sintering the ceramic substrate l and molybdenum or tungsten conductor pads formed on the alumina green sheet and the conductors in the through holes at a temperature of 1500°C or higher in a reducing atmosphere.) A nickel layer 3 is formed by plating on the conductor pad portion of the opening where the conductor 2 such as tungsten is shown, and then a copper or 4-way 2-A-4 connection pin 5 is attached using silver solder 4. There is. The composition of silver solder is generally Ag 60! A eutectic alloy of 40 mol-Cu is used, with a melting point of 779°C, and the processing temperature for brazing is about 810°C, in a hydrogen reducing atmosphere to prevent oxidation of conductors such as molybdenum. Next, the connection pins and conductors attached to the board are gold plated to prevent deterioration. Figure 2 shows a board with connection pins on which a gold layer 6 has been formed. The processing temperature is high, and it is difficult to heat fine thin film patterns formed on a substrate to this temperature.On the other hand, when forming fine thin film patterns such as signal lines after attaching pins to the substrate in advance, Also, in the case of packaging technology that uses organic insulating films (polyimide, etc.) to form patterns on multilayer ceramic substrates, the accuracy when forming various patterns on pinned substrates deteriorates, and the workability also decreases. But it's the same. Furthermore, brazing involves a step of gold plating the connection pins and conductor pads, resulting in poor workability.

Next, in order to lower the processing temperature, Au-8n or Au-8i, Au-8n-Pd) AAu-8n- was used as a brazing material.
A etc. were considered. A specific example is shown in FIGS. 3 and 4. In FIG. 3, a molybdenum layer 12 is attached to the surface of a ceramic substrate 11, and a thick film 13 is formed on the molybdenum layer by means such as plating. ′
Next, a gold coating 14 is applied to the nickel coating using gold paste.
Then, the connection bottle 16, which was plated with gold 17, was heated to form a gold-nickel solid solution.
8N brazing filler metal 15. In this method, the gold-nickel solid solution is formed at a temperature of about 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. The coating is coated with a group 1 metal layer 25 that serves as a source of an gettering metal, and then a connecting pin 27 plated with gold 28 is bonded by an Au-an' brazing material 26. In both cases, a gold layer 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 bottle is attached, which increases the process cost. This is disadvantageous both in terms of performance and cost, and heat treatments such as sb and brazing must be carried out in a hydrogen-reducing atmosphere to prevent oxidation of molybdenum. 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,
Compared to the conventional method using silver brazing material, heat treatment can be performed at low temperatures (below 400°C) and in a neutral atmosphere, and it does not require the application of a gold coating as a barrier as shown in other conventional methods. The object of the present invention is to provide a brazing method that does not require the formation of molybdenum pads on the parts, has a very simple structure, is advantageous in terms of workability and cost, and has sufficient pin bonding strength.

(Structure of the Invention) That is, the present invention includes a step of forming a titanium film on a portion to be brazed on a ceramic substrate, a step of forming a metal layer of Group 1 of the periodic table on the titanium film, and a step of forming a metal layer of Group 1 of the periodic table on the titanium film. and brazing the input/output electrical connection vias onto the Group I metal layer.

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

5 to 8 are diagrams showing the brazing method of the present invention, and FIG. 9 is a schematic diagram of a ceramic substrate with pins produced in an example. As shown in FIG. 5, a thin metal plate is formed on the upper surface of the multilayer ceramic substrate 31 by means such as etching, and a blank mask 32 is superimposed thereon. The multilayer ceramic substrate 31 may be made of an alumina green sheet, printed with molybdenum or tungsten as a conductor, laminated and pressed, and then sintered in a hydrogen reducing atmosphere at a temperature of 1500° C. or higher, or made of lead borosilicate crystallized glass and alumina. Gold, silver,
It may also be a so-called low-temperature sintered multilayer ceramic substrate printed with silver-palladium, gold-platinum, silver-platinum, etc. and sintered in an oxidizing atmosphere at 1000°C or less after lamination pressing.
In particular, a zero-order titanium film was formed using the latter substrate using silver-palladium.As shown in FIG. 6, 300 to 100 ox thickness of ≠ tan film 3
form 3. Continuing on from the titanium film formed in FIG. 6, a palladium layer 34 is formed from metals of group 1 of the periodic table, as shown in FIG. The palladium layer is formed by sputtering similar to the formation of a titanium thin film j) 10001-3
Formed to a thickness of 000X ◎ Sputtering is IQ
After reducing the pressure to below 10 torr, Ar gas was introduced to about 10 torr.
As can be seen from Figure 8, which shows a cross-sectional view when the mask is removed after forming a film of group metal, this method forms a titanium film directly on the surface of the ceramic substrate, which is different from other methods. One of the characteristics that is significantly different from that of the ceramic substrate having the metal pad portion obtained in this way is that the ceramic substrate having the metal pad portion obtained in this way is mixed with an alloy brazing filler metal with a weight ratio of 5 Oqb of gold and 20 qbf of tin.
It is placed on a plurality of input/output electrical connection pins 36 made of a material such as copal or 4.2 alloy, each having about 3 mg attached thereto, and bonded to a Balazicum layer, which is a group Ⅰ metal. FIG. 9 shows a schematic diagram of a multilayer ceramic board with connecting pins attached by the above method, and the surface of the metal pin 360 is coated with a gold coating layer 37 formed by plating or the like. Since the melting point of the alloy brazing filler metal with a weight ratio of 8011b and 20% tin is 280°C, the processing temperature was 300°C to 450°C for 10 to 30 minutes. A layer of metals from group 0, such as palladium, will cause gettering of the tin in the gold-tin brazing material, increasing the apparent ratio of gold to tin, and therefore after cooling or condensation of the brazing material. This has the effect of raising the melting point of the attached joint part.In this case, attaching a pin attachment is effective when there is a process of applying heat cycles afterwards. During brazing, the gold coating layer partially melts together with the gold-tin filler metal.The proportion of gold in the gold-tin filler metal increases, raising the melting point of the bonded part and producing the same effect. It will be done. The adhesive strength between the input/output electrical connection pins and the multilayer ceramic substrate brazed using this method is 4. OKt/
- Indicates the above, and shows sufficient strength as an input/output pin of a mounting board. (Effects of the invention) As described above, by adopting the brazing method of the present invention, brazing can be performed at temperatures below 400°C. At an extremely low temperature,
Moreover, it can be carried out in a neutral atmosphere, and there is no need to previously form a thick metal layer (molybdenum, tungsten, gold, silver, silver-palladium, etc.) for the pin pad on the surface of the ceramic substrate, and there is no need to form a gold film for the barrier. It has now become possible to obtain a substrate with bottles that has a simple structure that does not require any bonding and has sufficient adhesive strength. Furthermore, since the method of the present invention does not involve wet etching such as etching when forming the metal layer of the pin pad, it does not have any adverse effects on ceramics and can provide a highly reliable substrate with pins.
It is also advantageous in terms of workability and cost, and it is now possible to obtain substrates with pins that are sufficiently strong against later thermal cycles. Group 1 metals can also be used. Furthermore, instead of sputtering, film forming means such as timed vapor deposition, plating, and screen printing can be used.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams showing conventional pin-equipped ceramic substrates, 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. In Figure 0, which is a schematic diagram of a board with pins manufactured by the method, 1. IL 21,3
1... Ceramic substrate, 2. 12. 22...
Thick film conductor pad layer, 3°13.23...nickel layer,
4...Silver solder, L16t27・36°°°metal 1y
・6・ 17・ 28・ 37, -°. Gold coating layer %14...Gold coating, 15,26,35...
Gold-tin wax, 24... Gold coating, 25... Group ■ metal layer, 32... Mask, 33... Titanium film, 34...
・Group ■ metal film 0 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 3 Figure 7 Figure δ' Kabuto Figure 9

Claims (2)

[Claims] (1) A method of brazing metal connection pins to a ceramic substrate using a brazing material, which includes a step of forming a titanium film on the part to be brazed on the ceramic substrate, and a process of forming a titanium film on the periodic table on the titanium film. A brazing method comprising the steps of forming a Group 1 metal film and brazing a connecting pin onto the Group 1 metal layer using a brazing material. (2) Claim 1: The brazing material is a gold-tin brazing material.
The brazing method described in the section is ◎ ゛