초록 ▼

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 interengag

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 CO2 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: [Figure] where: C is the critical thermal radius, a is the Gaussian radius at 1/e2, 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.

대표청구항 ▼

A method of soldering one or more electrical lead strands to a printed electrical path, comprising the steps of: (a) planting said path on a ceramic substrate and attaching at least one solder pad to a portion of said printed electrical path; (b) forcing a surface portion of said electrical lead str

A method of soldering one or more electrical lead strands to a printed electrical path, comprising the steps of: (a) planting said path on a ceramic substrate and attaching at least one solder pad to a portion of said printed electrical path; (b) forcing a surface portion of said electrical lead strand into full interengagement with said pad with an engaging force sufficient to permit heat conduction therebetween for soldering, said portion of said electrical lead strand and pad constituting a soldering assembly; (c) directing a defocused laser beam onto said soldering assembly, and a beam-on time effective to exert a controlled thermal radius on said soldering assembly to reflow only a preselected portion of said pad and effect a solder joint between said pad and said strand portion, said joint having a strength of at least 400 grams; (d) the parameters of beam power, beam spot diameter, and beam on time-are optimally correlated by the following equation: [Figure] the critical thermal radius a is the Gaussian radius at 1/e2, ln is logarithm, Tm is the melting temperature of the solder minus the specimen temperature, P is the laser beam power it watts, A is the surface absorptivity of the solder at 10.6 microns, R is the thermal resistance per unit area of the system, tc is the ciritical time to bring the solder to the Tm temperature, c is the heat capacity of the system.