Electric heating – Metal heating – By arc
Patent
1983-01-24
1985-07-23
Envall, Jr., Roy N.
Electric heating
Metal heating
By arc
219121LC, 219121LD, 219121L, 219121EC, 219121ED, 338329, B23K 1500, H01C 114, H01C 1144
Patent
active
045310440
ABSTRACT:
A method of soldering electrical lead strands (of a width at least 0.3 inch) to a printed electrical path is disclosed. The path is planted on an alumina ceramic substrate and a solder pad is attached to a portion of the path. A flat surface portion of each lead strand is forced into full interengagement with a pad, a CO.sub.2 defocused laser beam is directed onto the soldering assembly with the beam controlled to have a beam power of at least 100 watts, a beam spot diameter no less than the width of the lead strand and no greater than the width of the pad, and a beam on-time effective to exert a controlled thermal radius on the soldering assembly to reflow only a preselected portion of the pad and effect a solder joint between the pad and strand portion, the joint having a strength of at least 400 grams. The parameters of the beam power, beam spot diameter, and beam on-time are optimally correlated by the following equation: ##EQU1## where: C is the critical thermal radius, a is the Gaussian radius at 1/e.sup.2, ln is logarithm, Tm is the melting temperature of the solder minus the specimen temperature, P is the laser beam power in watts, A is the surface absorptivity of the solder at 10.6 microns, R is the terminal resistance per unit area of the system, tc is the critical time to bring the solder to the Tm temperature, c is the heat capacity of the system.
REFERENCES:
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patent: 3520055 (1970-07-01), Jannett
patent: 3614832 (1971-10-01), Chance et al.
patent: 4278867 (1981-07-01), Tan
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patent: 4404453 (1983-09-01), Gotman
Thwaites et al., "Soldering Techniques & Equipment", Electronics Manufacturing, vol. 15, No. 3, Mar./Apr. 1969, pp. 21-29.
Saunders et al., "Lasers, Operation, Equipment, Applications and Design", McGraw-Hill Books Co., .COPYRGT.1980, pp. 78-82.
Envall Jr. Roy N.
Ford Motor Company
Johnson Olin B.
Malleck Joseph W.
Sears C. N.
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