In case you missed it: surface finishes."Reliability of Tin Terminated Components in a Lead-Free System" Authors: Jorge A. Manriquez, Ph.D., Oscar Molina, Juan C. Cardenas and Brian J. Toleno, Ph.D.; jmanriquez@itesm.mx. Abstract: This experimental study evaluated the effects on solder joint reliability using Pb-free solders and Sn-finished components on boards with Pb-base metalizations. Variables in the study were solder chemistry (Sn63Pb37, Sn95.5Ag3.8Cu0.7, Sn96.3Ag2.5Cu0.7Sb0.5) and thickness of nickel barrier (50 [micro]in, 30 [micro]in) below the tin finish of 0603 BaTiO3 ceramic capacitors. Test vehicles were HASL-SnPb10 finished. SMT (1) (Surface Mount Technology) See surface mount. (2) (Station ManagemenT) An FDDI network management protocol that provides direct management. Only one node requires the software. SMT - Station Management boards were assembled with printing parameters and reflow (1) The process of heating and melting the solder that has been screen printed onto a printed circuit board in order to bond chips and other components to the board. Surface mount chips (SMT) use the reflow method. Contrast with wave soldering. See also reflowable text. profiles optimized for each condition. Fillet fillet /fil·let/ (fil´et) 1. a loop, as of cord or tape, for making traction on the fetus. 2. in the nervous system, a long band of nerve fibers. fil·let n. 1. formation was inspected according to J-STD-001B. The first portion of the study is an isothermal i·so·ther·mal adj. Of, relating to, or indicating equal or constant temperatures. isothermal, isothermic having the same temperature. test at 125[degrees]C and 25V DC (MIL-STD-202G) to evaluate formations of CuSn and NiSn intermetallic compounds at solder-metal interfaces. Twenty-four boards with 20 capacitors each were evaluated. IMC (Internet Mail Consortium, Santa Cruz, CA, www.imc.org) An industry trade association founded in 1996 by Paul Hoffman and Dave Crocker that promotes Internet e-mail standards and features. thickness measurements were taken from samples after 0, 65, 130 and 264 hrs., using a SEM/EDX SEM/EDX Scanning Electron Microscope/Energy Dispersive Using X-Ray (Analysis) unit. Capacitance measurements were taken at the start and the end of the isothermal aging test. The second portion of the study used a thermal cycling stress condition (IPC-SM-785) using a +25/+100/+25[degrees]C cycle with 15 min. dwell time at each temperature extreme and a 15[degrees]C/min. heating/cooling step. Forty-two boards with 20 capacitors each were evaluated according to failing criteria by loss of electrical continuity and by maximum variation of capacitance. Growth of Cu3Sn and Ni3Sn IMCs along the soldermetal interfaces was very similar for all types of solder chemistries. All tested conditions produced assemblies that complied with expected reliability. Two capacitors presented a higher than 25% reduction in capacitance before 1000 hrs., both from the antimony antimony (ăn`tĭmō'nē) [Lat. antimoneum], semimetallic chemical element; symbol Sb [Lat. stibium,=a mark]; at. no. 51; at. wt. 121.75; m.p. 630.74°C;; b.p. 1,750°C;; sp. gr. (metallic form) 6. containing Pb-free solder joints when capacitors had a 30 [micro]in Ni barrier. The paper discusses results and proposes possible relationships between joint-level reliability and studied variables. (SMTAI, September 2005) |
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