Accession Number : ADA300853

Title :   The Reliability of Laser Reflowed Sn-Ag Solder Joints.

Descriptive Note : Quarterly rept. no. 4,

Corporate Author : RENSSELAER POLYTECHNIC INST TROY NY

Personal Author(s) : Raeder, C. H. ; Millard, D. L. ; Messler, R. W.

PDF Url : ADA300853

Report Date : 19 SEP 1995

Pagination or Media Count : 28

Abstract : Measurement of thermal cycling stress-strain hysteresis for soldered joints is described by several authors. In the first study to report experimentally measured thermomechanical (T-M) stress-strain hysteresis, only a single ceramic leadless chip carrier soldered to a fiberglass reinforced polymer (FR4) printed wiring board and a single thermal cycle was used throughout the study. These conditions prescribe one value of k' and one value of gamma sub fc. Only stable loop hysteresis was reported. The results were thus very limited. Y.-H. Pao used a 2-beam, model geometry very similar to that shown and a single temperature cycle to successfully measure the T-M hysteresis of a variety of Sn-based alloys. The stress-strain data were used to obtain constitutive relations describing the time, temperature and stress dependent deformation behavior of the test alloys under thermal cycling conditions. Experimental test assembly and solder joint configurations vary, but the approaches are, in theory, similar. The general approach is shown. If strain gages are attached to the top and bottom of either the component, substrate, or one of the beams representing these package elements in a model assembly, bending and elongation of the component or beam can be recorded. Bending in the other beam is either measured in the same way or assumed equal to that of the first beam. Stress in the solder joint is calculated from the elastic mechanical strain in the beam. Strain in the solder joint is calculated from the thermal and mechanical strain in the beams according to Equation 3.10. The solder joint being tested is a butt joint between two 1/8" diameter commercially pure copper rods.

Descriptors :   *PRINTED CIRCUIT BOARDS, *SOLDERED JOINTS, *TIN ALLOYS, THERMOMECHANICS, STRESS STRAIN RELATIONS, FIBERGLASS, LITERATURE SURVEYS, POLYMERS, DEFORMATION, STIFFNESS, FIBER REINFORCED COMPOSITES, ELASTIC PROPERTIES, MODULUS OF ELASTICITY, CHIPS(ELECTRONICS), SUBSTRATES, STRAIN(MECHANICS), LASER BEAMS, CERAMIC MATERIALS, STRAIN GAGES, CREEP, FATIGUE(MECHANICS), THERMAL FATIGUE, CALIBRATION, RODS, FAILURE(MECHANICS), THERMAL CYCLING TESTS, THERMAL STRESSES, HYSTERESIS, ELONGATION, REINFORCING MATERIALS, CYCLIC LOADS, BUTT WELDING.

Subject Categories : Electrical and Electronic Equipment
      Properties of Metals and Alloys
      Couplers, Fasteners, and Joints

Distribution Statement : APPROVED FOR PUBLIC RELEASE