GB2072073A - Soldering parts not readily solderable - Google Patents

Abstract

A method of making an article of metal parts required to be joined to each other, one, 11, or both, of said parts being made from a metal which does not readily lend itself to soldering, eg an alloy including Al and Zn, the method comprising the step of plating, at 12, at least the jointing surface of each such part which does not readily lend itself to soldering with a metal that does not readily lend itself to soldering eg Cu, Sn, Ag, and then joining said parts by soldering at 14, eg using a Pb and Sn solder. A Cu plating process is disclosed. <IMAGE>

Description

SPECIFICATION A method of joining articles The present invention relates to a method ofjoining metal parts to form an article by soldering.

Soldering is a process for joining metal parts by means of a molten filler metal whose melting point is lower than that of the metals to be joined. The molten filler metal contacts the metals to be joined to form a bond without causing the metals to be joined to be melted themselves.

Soldering together of metal parts as a method of joining an article is well known, some metals such as copper and tin being especially suitable for joining by a soldering process. Parts made from other metals, which readily oxidise such as aluminium, do not readily lend themselves to a soldering process, however these difficulties can be overcome. For example aluminium can be soldered using an ultrasonic soldering process, however such processes can be complicated, and depending on the nature of the parts to be soldered together, may not be suitable processes for all applications.

Parts of certain articles, for reasons of economy, production techniques or functional reasons, are often made from metals which do not readily lend themselves to a soldering process. A particular example of such parts are those formed as zinc alloy die castings, the composition of which includes aluminium and zinc. Such an alloy is just one example of a metal which does not readily lend itself to a soldering process.

It is an object of the present invention to overcome or reduce these difficulties.

According to the present invention we provide a method of making an article from metal parts required to be joined to each other by way of respective junction surfaces thereon and of which one or both is or are made of a metal which does not readily lend itself to soldering, and wherein that one or each of said parts is subjected to plating over its junction surface with a metal which readily lends itself to soldering, thereafter the parts are joined by way of said junction surfaces by soldering.

"Junction surface" means that area over which the parts would be in contact with each other except for the intervention of the plating metal and solder and includes a plurality of separated areas of such contact.

The plated area should extend over the whole of the or each junction surface required to be plated and over which it is desired that molten filler metal, used in the soldering operation, should flow.

Preferably, the plated area of each part that is plated is greater than the area of its junction surface.

This assists in achieving a satisfactory bond between the plating metal and the part itself.

In appropriate cases, e.g. where the size of one or more of the parts to be joined is not great, the whole of the part may be plated with a metal that is readily solderable.

Preferably, the readily solderable metal is copper but may be any other suitable metal such as tin or silver.

The soldered joint achieved by the method of the invention results in a secure joint between the parts and it is therefore important that the plating applied, at least overthe junction surface of the part or each part does not provide a weak link in the joint.

According to a further aspect of the invention we provide a method of making an article, one of the parts of which is made from a zinc alloy, the other part being made from a metal which is readily solderable, the parts having respective junction surfaces, said method comprising the steps of copper plating at least the junction surface part of said zinc alloy part, and subsequently joining the zinc alloy part to the other part by causing molten filler metal used in the soldering process to flow over the plated junction surface of the part and the junction surface part of the other part.

Preferably the zinc alloy part is a zinc alloy die casting and the other part to which it is to be joined, may be brass, copper, pewter or other solderable metal.

According to a still further aspect of the invention, we provide an article comprising at least two parts joined to each other by way of junction surfaces and, one or both of which is or are made of a metal which does not readily lend itself to soldering, the junction surface of each such part which is made from the metal which is not readily solderable being plated with a metal which is readily solderable, and said parts being joined together by molten filler metal used in a soldering process.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings wherein FIGURE 1 is a side elevation of a mug, the con tainerofwhich is made from a readily solderable metal and the handle from a zinc alloy die casting; FIGURE 2 is a fragmentary view on an enlarged scale of the junction surfaces of the handle of the container.

The mug comprises a container part indicated at 10 which is made from a readily solderable metal, for example pewter, brass, or copper, and a handle part 11 made from a zinc alloy as a pressure die casting.

The handle part 11 is first plated with copper by a process which will be described in more detail later.

The layer copper 12 in this example covers the whole surface of the handle part including the junction surface formed by the end surfaces of the handle part at its ends 13 overwhich it abuts the container part.

The end surfaces at which the handle part is to be joined to the container part 10 are tinned i.e. coated with a molten filler metal 14 (solder) usually a lead and tin solder. The container part 10 is heated at least over its junction surface where the handle part 11 is to be attached thereto to a temperature sufficient to melt the solder 14.

The handle part is then placed in the desired position with its end surfaces abutting the heated con The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

tainer part 10 thus melting the solder 14 and establishing a bond with the plating metal on the end surfaces of the handle part. The assembled article is then allowed to cool. The article may then, after cleaning, be plated with silver, for example, to provide an attractive finish.

The copper plating process to which the handle part is subjected is carefully controlled to provide that the bonding between the copper plating 12 and the zinc alloy die cast handle part 11 is strong and does not provide a weak link in the joint between the handle part and container part.

In general terms the standard of the plating, including the cleanliness of the surface to be plated, the quality of the ingredients of the plating bath and the thickness of the plated layer, desirably should be such that the strength of adherence of the plated layer to the junction surface is not significantly less than the strength of adherence of the solder to the plated layer.

One example of a plating process will now be described, which process has been found to provide a satisfactorily strong bond between the plating layer 12 and the handle part 11.

The pressure die cast handle part is subjected to the following treatment prior to the soldering operation by means of which it is attached to the container part of the mug: (1) degreasing by use of a degreasing agent such as that sold under the product name Triklone N; (2) soaking in hot alkaline cleaner such as that sold under the product name Prezin; (3) subjection to a cathodic cleaner such as that sold under the product name Anozin; (4) a cold water swill; (5) a 10% sulphuric acid dip; (6) cold water swill; (7) a first copper plating process in a bath containing copper cyanide; (8) a cold water swill; (9) a further cold water swill; (10) a second copper plating process in a bath containing copper phosphate, the copper deposit is a thickness of 0.0003 inches; (11) a cold water swill; (12) a further cold water swill; (13) a chromium passivation process; ; (14) a cold water swill; (15) a further cold water swill; (16) a drying operation; The application of the layer of solder and establ ishment of a bond between that and the plated sur faces of the handle part on the one hand and the junction surface of the container part on the other hand may be effected by any suitable soldering pro cess.

Thus, the soldering process may, as aforemen tioned, comprise firstly tinning the end surfaces of the handle part 11 and then warming the container part 10 so that when the handle part 11 is applied to the container 10, the solder 14 melts.

Claims (16)

1. A method of making an article from metal parts required to be joined to each other by way of respective junction surfaces thereon and of which one or both is or are made of a metal which does not readily lend itself to soldering, and wherein that one or each of said parts is subjected to plating over its junction surface with a metal which readily lends itself to soldering, thereafter the parts are joined by way of said junction surfaces by soldering.

2. A method of making an article as claimed in claim 1 wherein the plated area extends over the whole of the or each junction surface.

3. A method of making an article as claimed in claim 1 or claim 2 wherein the plated area of the or each part is greater than the area of its respective.

junction surface.

4. A method of making an article as claimed in any one of the preceding claims wherein the whole of the or each part is plated with a metal that is readily solderable.

5. A method of making an article as claimed in any one of the preceding claims wherein the readily solderable metal is copper.

6. A method of making an article as claimed in any one of claims 1 to 4 wherein the readily solderable metal is tin.

7. A method of making an article as claimed in any one of claims 1 to 4 wherein the readily solderable metal is silver.

8. A method of making an article as claimed in any one of the preceding claims wherein one of said parts is made from zinc alloy.

9. A method of making an article as claimed in claim 8 wherein both of said parts to be joined together are made from a zinc alloy.

10. A method of making an article as claimed in claim 8 or claim 9 wherein said part or parts comprise a zinc alloy die casting.

11. A method of making an article one of the parts of which is made from a zinc alloy, the other part being made from metal which is readily solderable, the parts having respective junction surfaces, said method comprising the steps of copper plating at least the junction surface part of said zinc alloy part, and subsequently joining the zinc alloy part to the other part by causing molten filler metal used in the soldering process to flow over the plated junction surface of the part and the junction surface of the other part.

12. A method of making an article as claimed in claim 11 wherein the zinc alloy part comprises a zinc alloy die casting and said part to which it is to be joined comprises a brass, copper or pewter part or a part made from other readily solderable metal.

13. An article comprising at least two parts joined to each other by way of junction surfaces and, one or both of which is or are made of a metal which does not readily lend itself to soldering, the junction surface of each such part made from metal which is not readily solderable being plated with a metal which is readily solderable, said parts being joined together by molten filler metal used in a soldering process.

14. A method of making an article substantially as hereinbefore described.

15. An article substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

16. A method of making an article substantially as hereinbefore described and comprising the steps numbered 1 to 16 in the accompanying description.