SK7925Y1 - Method of direct soldering by means of common soldering material and intermediate layer for direct soldering - Google Patents

Abstract

Two layers of common solder (3) are placed between two soldered surfaces of material. An intermediatelayer (4) of active metal is placed between these two layers of the common solder (3). Afterwards both layers of the solder (3) and the intermediate layer (4) of active metal are heated to soldering temperature wherein the temperature is equal or higher than the melting temperature of the common solder (3) and at the same time it is equal or higher than activation temperature of the active metal in the intermediate layer (4). The soldering is performed using of the common solder that does not contain an active metal and directly without previous metal-plating of the soldered surface, thereby fast and effective process is achieved, and the formed soldered joint is stable, without ruptures and with high firmness at the limit of firmness of the used common solder (3).

Description

The invention relates to the soldering of difficult-to-solder materials by means of a conventional solder without prior metallization of the surface of the materials, whereby the wettability of the conventional solder is achieved even on non-wetting surfaces. The technical solution also describes an intermediate layer used for soldering.

BACKGROUND OF THE INVENTION

Several methods are known for soldering difficult-to-solder materials, such as ceramic materials (e.g., Al ₂ O ₃ , SiO ₂ , TiO ₂ , etc.), some non-metallic materials (Si, Ge, graphite, etc.) or some metallic materials ( W, Mo, Ta and the like). These materials can be soldered indirectly by first applying a solderable metal coating to the surface before the soldering itself is realized. Surface plating eliminates the problems associated with the wettability of ceramic materials and some non-metallic materials. The necessary solderable metal coating is obtained by:

By burning metal solutions of either refractory metals Mo, Mn, W (followed by nickel plating), or precious metals Ag, Au, Pt, etc., by physical and chemical deposition to form thin coatings, e.g. Au, Ag, Ni and combinations thereof.

The formed solder coating provides the necessary wettability of the otherwise non-wettable surface of the material (e.g. as in US 4,312,896). This makes it possible to use conventional solders that are available in a very wide range of properties. The disadvantage is a complicated multi-step procedure that requires the use of specialized equipment.

The second approach when soldering difficult-to-solder materials is to use a special, so-called solder. The active element is an important component of the solder, providing wettability and bonding between the metal solder and the solder material. Such direct soldering (e.g. according to US2016 / 0228966) shortens the technological time, improves the hygiene of the working environment. The disadvantage of using active metal in solders is the small range of solders available with active metal over conventional solders, which are available for a variety of applications and for different pairs of solder materials.

U.S. Patent Publication US 2002/0038813 A1 discloses the use of an active metal layer suitable for specific Au-based solders, respectively. Au-Ag. The disadvantage is the low universality of the obvious method.

It is desired and not known to provide a technical solution which will provide the advantages of using a conventional solder with the advantages of direct soldering, while maintaining the speed of the process while achieving good solder joint properties.

The essence of the technical solution

The above-mentioned drawbacks are substantially eliminated by the direct soldering method using a conventional solder in the form of a layer without prior plating of the surface of the solder material according to the present invention, which consists in placing two layers of conventional solder intended to adhere between two soldered surfaces. an intermediate layer of active metal is placed between the two layers of the conventional solder and subsequently both the solder layer and the active metal intermediate layer are heated to the brazing temperature. The brazing temperature is equal to or higher than the melting point of a conventional solder and at the same time equal to or higher than the active metal activation temperature. The activation temperature of the active metal will usually be lower than the melting point of the active metal.

The term direct soldering indicates that the process does not need to prepare the surfaces by applying auxiliary layers. The term conventional solder includes all known solders without significant active metal content. In particular, the active metal may be Ti, Zr, Hf, Cr, La, Y, Ce, Pr, Mg and alloys thereof or combinations thereof. By significant content is meant such a proportion of the content or volume of the solder that exhibits the effects of the active metal in the solder, thus not a contaminant or trace amount.

Naming the active metal layer as an "intermediate layer" expresses the position of the layer, but does not determine in which order the intermediate layer is to be laid, for example the intermediate layer may be deposited as a second layer in the order of conventional solder / active metal interlayer / conventional solder layer.

As it has been shown in the invention, the relatively thin layers of a conventional solder have a positive effect on its ability to wet the surface of the solder material. The active metal diffuses through the molten solder layer into both solder layers and positively affects its wettability. Under these conditions, the effects of the new method of direct soldering are achieved, wettability is ensured and the

SK 7925 Υ1 between the metal solder and the difficult to solder material without the need to melt the active metal at high temperature.

The new direct brazing method is applicable to vacuum brazing or ultrasonic brazing of ceramic and other difficult-to-solder materials without the need for coating and without the use of a special active solder. A conventional solder, which is available with different properties, is used to make the joint. Vacuum brazing is recommended for brazing and high-temperature brazing. Ultrasonic soldering is particularly suitable for soft soldering.

The solder layer may be in the form of a foil, which allows the layer to be cut to the necessary shape that corresponds to the plan view of the joint. In another embodiment, the solder layer may be formed by applying a paste which mainly consists of a solder metal powder and a fluid. The paste can be precisely applied by means of stencils or by screen printing, or by other methods known in the art. The conventional solder can be soft, hard or high temperature. It is important that the solder temperature appropriate for the solder corresponds at least to the active metal activation temperature. The brazing process according to the invention can be carried out under vacuum at a higher temperature or in air using a lower brazing temperature, where it is necessary to locally raise the temperature of the interlayer to the value of activation of the active metal. For example, the energy supplied by ultrasound to the solder location can be used for this purpose.

The active metal layer may be in the form of a film or a paste. In particular, the active metal may be Ti, Zr, Hf, Cr, La, Y, Ce, Pr, Mg and alloys thereof or combinations thereof. In the case of a film, its thickness will be in the range of 0.0001 to 1 mm.

It has also been found, when inventing a new direct soldering method, that the use of three layers better compensates for residual stresses in the joint resulting from the different thermal expansion of different solder materials, such as ceramic and metal. This prevents the ceramic part of the joint from cracking immediately after soldering or during thermal cycling in operation. The joint also has a greater thickness, which increases the strength of the ceramic / metal joints. The terms first brazed material and second brazed material distinguish between different materials, for example, ceramic and metal, or glass and metal. The terms 'first' and 'second' are merely distinct, do not indicate explicit order or importance, and are therefore interchangeable.

An essential advantage of the present invention is therefore not only rapid direct soldering of difficult-to-solder materials using conventional solder, but also high quality and stability of the formed joint. The use of conventional solder simplifies and lowers the process, whereby all available conventional solders of a wide variety of available solders can be combined with the active metal intermediate layer. Thus, there is no need to develop and produce a special active metal solder for the respective pair of difficult-to-solder materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution is explained in more detail with reference to Figures 1 and 2. The particular shapes and thicknesses of the soldered materials, solder layers and interlayers are illustrative only and are not to be considered as limiting the scope of protection.

Figure 1 shows the layers used in soldering ceramic and metal.

Figure 2 shows solder layers deposited by screen printing between which an intermediate layer of active metal is interposed when soldering two ceramic materials.

EXAMPLES

Example 1

In this example of Figure 1, the brazed ceramic Al ₂ O ₃ with stainless steel is made of a conventional Ag72Cu silver based solder 3, which is in the form of a foil. A thin sheet of pure Ti was used to form the intermediate layer 4 of active metal.

The joint assembly prior to thermal exposure is as follows: first brazed material 1 - ceramics A1 ₂ O ₃ , conventional solder 3 - Ag72Cu, intermediate layer 4 - Ti foil, common solder 3 - Ag72Cu, second solder material 2 - stainless steel.

After formation of the stack, the sheets were soldered under vacuum at 890 ° C. In the brazing process, the intermediate layer 4 partially dissolved in the conventional solder 3, and the titanium of the intermediate layer 4, by its activity, provided wetting of the ceramic material as well as better wetting of the stainless steel.

SK 7925 Yl

Example 2

When soldering a SiC ceramic with a smith, a tin-based SnAg5 tin solder in foil form was used as conventional solder 3. A thin film of pure Ti was used to form the intermediate layer 4 of the active metal.

The joint assembly prior to thermal exposure is as follows: first brazed material 1 - SiC ceramic, conventional 3 - SnAg5 solder, 4 - Ti film interlayer, common 3 - SnAg5 solder, second 2 - covert solder.

The joint was soldered under vacuum at 850 ° C. In the brazing process, the titanium from the interlayer 4 partially dissolved in the conventional solder 3 and the titanium by its activity ensured the wetting of the ceramic material. The formed joint is free of cracks and the joint strength corresponds to that of the conventional solder 3 used.

Example 3

The direct soldering method in this example is used to solder the Al2O3 ceramic transition pieces.

Example 4

The heat exchanger is soldered to the ceramic substrate using conventional solder 3 and active metal intermediate layer 4.

Example 5

The direct soldering method in this example is used in soldering ceramic and non-metallic sputtering targets, for example magnetron sputtering.

Example 6

The metal contacts are soldered to the glass by means of two layers of conventional solder 3, between which there is an intermediate layer 4 of active metal.

Example 7

The ceramic components of Figure 2 are brazed to one another without prior coating of the respective surfaces, wherein the conventional solder 3 layer on the first solder material X as well as the active metal intermediate layer 4 are formed by applying a common solder paste 3 and active metal paste.

Industrial usability

Industrial applicability is obvious. According to this invention, it is possible to industrially and repeatedly braze materials with a poorly wettable surface using a conventional solder using an active metal interlayer. The technical solution will find application especially in the electronic, electrical, automotive, vacuum technology and the like.

PROTECTION REQUIREMENTS

Claims (10)

Method for direct soldering by means of a conventional solder in the form of a layer without prior plating of a solder surface, in which the conventional solder (3) is heated to a soldering temperature, characterized in that two layers of conventional solder (3) are placed between two soldered surfaces; which are intended to adhere to the brazed surfaces, an intermediate layer (4) of active metal is placed between two layers of conventional solder (3) and subsequently both layers of solder (3) and intermediate layer (4) are heated to a brazing temperature equal to or it is higher than the melting temperature of the conventional solder (3) and at the same time it is equal to or higher than the activation temperature of the active metal in the intermediate layer (4). 2. The direct soldering method according to claim 1, characterized in that the activation temperature of the active metal in the intermediate layer (4) is lower than the melting point of the active metal. The direct soldering method according to claim 2, characterized in that the active metal in the intermediate layer (4) is one of the metals of the group Ti, Zr, Hf, Cr, La, Y, Ce, Pr, Mg and / or an alloy thereof, and / or a combination thereof. Method of direct soldering using a conventional solder according to any one of claims 1 to 3, characterized in that the first solder material (1) and / or the second solder material is ceramic and / or glass, and / or metal. SK 7925 Yl A direct soldering method using a conventional solder according to any one of claims 1 to 4, characterized in that it is soldered under vacuum with a braze or a high temperature conventional solder (3). Method of direct soldering by means of a conventional solder according to any one of claims 1 to 4, characterized in that it is soldered with a soft conventional solder (3), wherein the ultrasound increases 5 shows the temperature between the layers (4). A direct soldering method using a conventional solder according to any one of claims 1 to 6, characterized in that the layer of conventional solder (3) is in the form of a foil. A direct soldering method using a conventional solder according to any one of claims 1 to 7, characterized in that the conventional solder layer (3) is in the form of a paste which is applied to the surface of the first solder material and / or the second solder material (2). ). The direct solder intermediate layer according to any one of claims 1 to 8, characterized in that the intermediate layer (4) is in the form of a paste which is applied to the conventional solder layer (3). A direct soldering intermediate layer according to any one of claims 1 to 8, characterized in that it is in the form of a foil having a thickness of 0.0001 to 1 mm.