Title :
Kinetic interactions of copper, lead and tin on solder coated PC boards studied using X-ray diffraction
Author :
Chason, Marc ; Hong, Jauwhei
Author_Institution :
Motorola Inc., Schaumburg, IL, USA
Abstract :
X-ray diffraction has been used to monitor the growth and decay of the constituent phases existing in solder (60% Sn-40% Pb) coated Cu printed circuit boards. Samples were aged from 145°C to 175°C for times sufficient to allow the Cu3Sn intermetallic phase X-ray peak count rate to exceed that for the Cu6Sn5 phase. Activation energies have been determined for the growth of (1) Cu6Sn5 and Cu3Sn and (2) the dissolution of crystalline from the solder matrix. The data indicate that the activation energy for Cu6Sn5 growth is Sn concentration dependent and can be related to the Sn solubility in Pb. The activation energy for Sn dissolution is not comparable to Sn lattice diffusion. A compressional d-space change in the Pb lattice induced by dissolved Sn is observed. The Pb(111) orientation is observed to grow preferentially during aging at all measured temperatures
Keywords :
X-ray diffraction examination of materials; copper; copper alloys; lead alloys; printed circuits; reliability; soldering; tin alloys; 145 to 175 C; Cu3Sn intermetallic phase; Cu6Sn5 phase; Pb lattice; SnPb-Cu; X-ray diffraction; activation energy; coated Cu printed circuit boards; compressional d-space change; kinetic interactions; solder coated PC boards; Aging; Copper; Kinetic theory; Lattices; Lead; Monitoring; Printed circuits; Temperature measurement; Tin; X-ray diffraction;
Conference_Titel :
Electronic Manufacturing Technology Symposium, 1989, Proceedings. Seventh IEEE/CHMT International
Conference_Location :
San Francisco, CA
DOI :
10.1109/EMTS.1989.68992
