Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
UK takes lead on lead-free soldering
Keywords PCIF, ITRI, Lead-free soldering
Working together to help electronics manufacturers deal with increasing commercial and legislative pressure to remove lead-bearing solder from their products, the PCIF and ITRI Ltd (formerly the International Tin Research Institute) are recommending that tin-silver-copper (Sn-Ag-Cu) alloys be accepted as a general replacement for tin-lead (Sn-Pb).
Sn-Ag-Cu has been chosen as a multi-purpose lead-free solder from the myriad available alloy types as it is considered to be suitable for surface mount, wave and hand soldering and for use in a variety of products. As well as being supported by the PCIF, this choice of alloy is backed by UK solder suppliers Alpha, Heraeus, Indium Corporation, Kester, Multicore and Senju. America's IPC (Association Connecting Electronics Industries) and NEMI (National Electronics Manufacturing initiative) are also implementing this recommendation in their lead-free roadmaps.
Alloys within the composition range of Sn-[3.4-4.l]Ag-[O.45-O.9Cu] are recommended. This range includes the four most commonly available solders (Sn-4Ag-O.5Cu, Sn-3.8Ag-O.7Cu, Sn-3.6Ag-O.5Cu and Sn-3.5Ag-0.7Cu), the current preference being for those with the higher silver content. The recommendation does not preclude the use of other alloys such as Sn-Cu, Sn-Ag, Sn-Ag-Cu-Sb, Sn-Bi-Ag and Sn-Zn-Bi which electronics manufacturers may opt to use for specific purposes.
In selecting these alloys, consideration has been given to the likelihood that it could be many years before the solderable finishes on all printed circuit boards and all component leads/terminations are lead-free. Consequently, all the recommended alloys can, if necessary, be used to solder PCBs and/or components with tin-lead finishes.
Uxbridge, Middlesex based ITRI, which has been involved in lead-free solder development for over a decade, is promoting these recommendations via its recently launched lead-free soldering information and research operation, Soldertec. A data sheet entitled "Lead-free alloys - the way forward" provides details of the recommended types, including comparisons of their relative solderability, processability, reliability, cost and other significant parameters.
Commenting on the release of the recommendations, PCIF Executive Director Brian Haken said: "The electronics manufacturing industry has been aware for some time that tin-lead solder will have to be eliminated and that there is no 'drop-in' replacement available. With more than 70 alternative alloys on offer, this narrowing down of the choice to a small family of alloys is precisely what the industry needs".