Processes for soldering aluminum-containing workpieces

• US 4,121,750 A
• Filed: 10/04/1976
• Issued: 10/24/1978
• Est. Priority Date: 12/15/1969
• Status: Expired due to Term

• Current Assignee: Vereinigte Aluminium-Werke AG
• Original Assignee: Vereinigte Aluminium-Werke AG
• Inventors: Schultze, Werner, Schoer, Heinz
• Primary Examiner(s): Dost, Gerald A.
• Assistant Examiner(s): Bell, Paul A.
• Application Number:
  US05/729,039
• Time in Patent Office: 750 Days
• Field of Search: 75/178 A, 75/148, 75/146, 75/149, 228/219, 228/263
• US Class Current: 228/219
• CPC Class Codes: B23K 35/286 Al as the principal constituent
• CPC Class Codes: B23K 35/288 with Sn or Zn

Abstract

Processes and compositions for soldering aluminum-containing workpieces wherein the solder contains components which lower the surface tension and the viscosity of the molten solder, and which lower the interfacial tension between the solder and the aluminum-containing workpieces. Useful components are bismuth, strontium, barium and antimony. The solder may be used with or without flux.

Claims

1. A method of joining aluminum workpieces bearing an aluminum oxide surface layer which comprises:

interposing between said workpieces an aluminum-silicon filler material consisting essentially of aluminum containing from 6 to 20% by weight of silicon and from 0.01 to 10.0% by weight of an aluminum wetting agent selected from the group consisting of bismuth, antimony, strontium and barium,

heating said workpieces in contact with said filler material with a heating device to a temperature in the range from about 590°

C. to about 605°

C. wherein the resulting viscosity and surface tension of said filler material at said temperature is less than the viscosity and surface tension of said filler material in the absence of said wetting agent and the interfacial tension between said filler material and said workpieces is lower than the interfacial tension in the absence of said wetting agent and,

performing said heating step in a substantially non-oxidizing atmosphere and in the absence of a flux.

2. A method as defined in claim 1 wherein said filler metal contains about 0.05 to 2.0% by weight of said substance.

3. In the method of joining aluminum containing workpieces which comprises heating in contact with said aluminum containing workpieces a filler metal having a normal viscosity and a normal surface tension in its molten state and a normal interfacial tension between said molten filler metal and said workpieces, the improvement which comprises:

interposing between said workpieces a filler metal consisting essentially of zinc, about 2 to 25% by weight of aluminum, up to about 1% by weight of manganese and about 0.01% to about 10.0% by weight of at least one substance selected from the group consisting of bismuth, strontium, barium and antimony to substantially decrease the normal interfacial tension between said molten filler metal and said workpieces and to lower the normal viscosity and the normal surface tension of said molten filler metal,

maintaining said workpieces and said filler metal in a substantially non-oxidizing atmosphere,

non-exothermically raising the temperature of said filler metal in said substantially non-oxidizing atmosphere until said filler metal has reached a molten condition, said temperature raising step being performed in the absence of a flux and said filler metal being raised to a temperature substantially below the melting point of aluminum.

4. A method as defined in claim 3 wherein said filler metal is free of Si.

5. A method as defined in claim 3 wherein said filler metal contains up to 26% by weight of aluminum.

6. A method as defined in claim 3 wherein said filler metal contains at least 26% by weight of aluminum.

7. In the method of joining aluminum workpieces which comprises heating in contact with said aluminum workpieces an aluminum-silicon filler metal having a normal viscosity and a normal surface tension in its molten condition and a normal interfacial tension between said molten filler metal and said workpieces, the improvement which comprises:

interposing between said workpieces an aluminum-silicon base filler metal containing at least about 0.01% by weight of at least one substance selected from the group consisting of bismuth, strontium, barium and antimony to substantially decrease the normal interfacial tension between said molten filler metal and said workpieces and to lower the normal viscosity and the normal surface tension of said molten filler metal,

maintaining said workpiece and said filler metal in a substantially non-oxidizing atmosphere,

raising the temperature of said filler metal with a heating device in said substantially non-oxidizing atmosphere until said filler metal has reached a molten state, and

performing said temperature raise in the absence of a flux and said raised temperature being substantially below the melting point of aluminum.

8. A method as defined in claim 7 wherein said filler metal comprises at least 6% by weight of Si.

9. A method as defined in claim 7 wherein said filler metal comprises substantially 6-20% by weight of Si and substantially 0.01 to 10% by weight of said substance.

10. A method as defined in claim 7 wherein said filler metal comprises at least one substance selected from the group consisting of Cu, Mg, Ni, Sn, Zn, and Cd.

11. A method as defined in claim 10 wherein said filler metal comprises substantially 0.05 to 4.7% by weight of Cu where present, substantially 0.05 to 10% by weight of Mg where present, substantially 0.03 to 4% by weight of Ni where present, substantially 0.03 to 12% by weight of Sn where present, substantially 9.3 to 10.7% by weight of Zn where present, and substantially 0.03 to 12% by weight of Cd where present.

12. A method as defined in claim 11 wherein the remainder of said filler metal is substantially Al.

13. A method as defined in claim 7 which comprises raising the temperature of said filler metal to between about 590°

C. and about 605°

C.

14. A method as defined in claim 7 which comprises maintaining said workpieces and said filler metal at a pressure greater than about 10^-1 torr. during said joining operationg.

15. A method as defined in claim 7 wherein said filler metal contains about 0.05 to 2.0% by weight of said substance.

16. A method as defined in claim 7 wherein said filler metal contains up to about 10% by weight of said substance.