26th International Spring Seminar on Electronics Technology May 8 zyxwvut - 11,2003, zyxwvut Star6 Lesni, Slovak Republic Influence of combined metal Ni + Au resist on properties of connection between devices and PCB Frantisek Steiner, Ale5 HamaEek Department of technology and measurement University of West Bohemia Pilsen, 306 14, Czech Republic Phone + 420 377634 535, 533; zyxwvut Fax + 420 377634 502; steiner@.ket.zcu.cz, hamacek@,ket.zcu.cz zyx Abstract Incoming term zyxwvutsrqpo of the lead removing from the soldering process in production of electronic devices brings many problems. Except zyxwvutsr of very often advertised searching of classic SnPb solder replacement it is also necessary implement corrections in the process of PCB production. Here SnPb alloys are exploited like resist for PCB etchinp. One of SnPb resist replacement is combined metal Ni+Au resist.'Ni+Au resist, as well as used SnPb solder replacement, affects Jinal properties of connection between devices and printed circuit boards. Paper deolu with comparing ofproberties ofprimary "lead" way of devices mounting to PCB with newer lead-free zyxwvutsrq way. erploiting Ni+Au resist in PCB production. Comparing will be makedfor wide-spread mountingprocess, that is soldering, as well asfor alternative way, that is sticking with elecrricolly conductive adhesives 1. INTRODUCTION On the present many producers are looking for the best replacement of SnPb solder. Some producers are developing lead-free solders and second group of producers chose alternative replacement by adhesives. The reason of these activities is incoming term of lead elimination from the production of electronic devices. The elimination of lead from electronic devices production isn't related only to the replacement of SnPb solder. We also use lead in a process of printed circuit board production, for example we use lead in HAL technology. That is why we have to concentrate on SnPb solder replacement hut also we have to pay attention to next technology associated with electronic devices production. There is one more problem in production of PCB. It is related to surface mount devices. SMDs with pin grid lower than 2,54 nun require higher flatness of pads. This flatness isn't possible to achieve with HAL technology. One way of those problems solutions in production of printed circuit boards is an application of Ni and Au galvanic coating like etching resist. 2. TECHNOLOGY OF PRINTEDCIRCUIT BOARD PRODUCnON The elimination of lead from PCB production results in modification of production technology. First, the most widespread, way is surface finish by chemical Ni coating and following immersion Au coating. Next way of surface finish is chemical or immersion Sn coating. Cu surface of PCB for consumer electronics can be finished by passivation with organic coating (at preservation of good solderability). All these operations presuppose using of galvanic Sn coating as resist resistant to alkali etch bath. In recent years new way of PCB production overran. In this technology we use galvanic Ni coating in combination with galvanic Au coating as etching resist. Galvanic Ni and Au coating as etching resist At loading of this technology it zyx starts from experiences of good nickel solderability. Corrosive immunity is increased with galvanic Au coating. This technology is identified firstly for development samples production and for small-lot production. No small effect is aesthetic look this way produced PCBs. 26th ISSE 2003 293 0-7803-8002-9/03/$10.00 82003 IEEE