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Attaching solder spheres to bare copper

1998

I want to attach Sn10/Pb90 solder spheres to bare copper. I do not wish to use solder paste or flux to aid attachment. I also want to avoid plating the copper with solder (this would require buss lines within my layout because I do not know of any electroless solder plating technique). How can I do this?

Any help is greatly appreciated.

Thank You,

Dennis Fall
Thin Film Technology - North Mankato, Minnesota

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Dennis,

You didn't mention if your application would be amenable to pure tin instead of tin/lead. Electrochemicals in Maple Plain, MN makes two non-electrolytic products that may work in your application. They are M-Tin and O-Tin. M-Tin produces an immersion deposit and the thickness is self-limiting (=40µ"), while O-tin is an electroless tin and capable of thicker deposits. I have had great success with both of these products, not only in applications like you have described, but also in restoring solderability to component leads and other parts that have oxidized beyond the point of being solderable. The important thing to remember is that the effective solderability is short-lived and assembly should occur as soon as possible after deposition of the tin. You also may be able to simply brighten the copper with an ammonium persulphate/hydrogen peroxide solution and assemble immediately. Regards,

Keith Wicklund, CEF-SE
avionics - Minneapolis, Minnesota
1998

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1999

Dear sir/madam I am currently researching a project for Mallinckrodt Nellcor Puritan Bennett, Galway. The project involves connecting two wires to an emitter and two wires to a detector. The wires are tinned and approximately .5mm in diameter. The wires are currently being soldered to the detectors and emitters using a hand held soldering iron and a fixture for the emitters and detectors. I am looking for ways of soldering or crimping the wires to the components. The components may be manufactured with hollow legs and I am trying to find a way of guiding the wires into the legs as the measurements are to small to do accurately without the aid of a guide. Do you have any suggestions on guiding the wires or do you know of any other method of crimping the wires? The emitters and detectors are approximately 4mm*4mm with the legs sticking out approximately 3mm. Could a solder paste be used for the application? I would appreciate your opinion on this matter.

Yours sincerely,

Garry Lohan

I would like to know if you know anything about fluxless solders used for industrial purposes. Its used to repair aluminum and galvanized metal. It can be applied with a common propane torch. It has a tensile strength of about 40,000 lbs sq. inch. There's a web site called Alumaloy that describes it. I understand its been around for many years and it is in public domain. I think it was developed by Bell Labs a while back. I would like to know if its possible to know where I can find out more about its origins. Max

Max Moscus
self - Deerfield Beach, Florida
1999