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Fluxless Soldering

IP.com Disclosure Number: IPCOM000093945D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Sopher, RP: AUTHOR [+2]

Abstract

This process increases soldering yields, prevents voids in final soldered joints and eliminates charred flux. The presence of a flux, not shown, on solder-coated lands 20 can produce voids in one or more solder joints when gold-plated copper or nickel 22 contacts of semi-conductor 24 are joined to the lands in a solder reflow joint.

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Fluxless Soldering

This process increases soldering yields, prevents voids in final soldered joints and eliminates charred flux. The presence of a flux, not shown, on solder- coated lands 20 can produce voids in one or more solder joints when gold-plated copper or nickel 22 contacts of semi-conductor 24 are joined to the lands in a solder reflow joint.

As an alternative, the contacts 22 can be joined to land 20 without flux in a reflow cycle. This is conducted in a reducing atmosphere of H2 within a temperature range of about 330 degrees to 500 degrees C. Forming gas is satisfactory for the atmosphere, provided the heating operation is performed at a temperature of 400 degrees to 500 degrees C. Temperatures above 500 degrees C adversely affect P-type semiconductor material. The reflow temperature cycle should not exceed five minutes.

Other environments can also be employed in the process, as for example, argon, nitrogen and a vacuum. These environments are satisfactory, provided oxygen and water contents are minimized and cleanliness and temperature compatibility are maintained. The high side of the temperature range of 400 degrees to 500 degrees C. must be used with these environments.

This fluxless process is also used to solder positive standoffs, such as Cu spheres, to contacts 22 on semiconductor 24.

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