Any of the immersion coatings would perform well regards improved (tighter) diametric tolerance versus solder-coated barrels, and as gold and OSP have already been commented upon I'll add white (non porous) immersion tin as another alternate choice. Our experiences with white tin are in complete agreement with IBM's 1984 study of that finish ("Immersion Tin: It's chemistry, metallurgy and application in electronic packaging technology", 1984, Z. Kovac, K.N. Tu, IBM, IBM Joint Resource Development VOL 28 No 6.). While this paper does not report upon press-fit pins specifically, we have a substantial number of back panels in the field supplied to various OEM's - many in severe service environments - with a practical history of zero line or field failures as concerns the assembly performance of the pins. Our clients' appreciation for white tin includes: - allowance of PTH diametric tolerances down to +/- .0015" - improved ductility versus nickel - affinity for dissolution into all tin-based solder alloys - excellent wicking - good response in wide range of fluxes - very low cost - does not introduce a third metal to solder pots - no embrittlement issues - no environmental issues - infinite shelf life In addition to tin (and the previous comments on OSP and gold) silver and palladium might also be investigated (although I have no practical experience in the latter). Cheers! Bob Lazzara Circuit Connect Tech Support Georgia Service Bureau TEL: 800.560.9457 FAX: 888.453.0520 BBS: 603.889.5385 alternate eMail: [log in to unmask] -----Original Message----- From: Jim Herard <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: Tuesday, February 02, 1999 8:22 AM Subject: Re: [TN] : Press-fit with Immersion NiAu or OCC >Press Fit with OSP (organic coating over copper such as Benzyl Trimidizole >(sp?)) works very successfully. However, some manufacturing process >changes may be required depending upon the press fit pin style and >plating. The lack of SnPb on the board does increase insertion forces to >some degree. > >Cross sections should be taken when working with Ni/Au plated vias, as the >Ni is not as ductile as the copper, and some barrel cracking may occur, >depending upon pin design and forces. > >Hope that helps. > >Jim Herard >Mail/Dept BNLE >Mgr, FJUW, 3rd shift Test and Inspect >IBM Interconnect Products , Microelectronics Div >Endicott NY 13760-5553 >t/l 857-7026 > >################################################################ >TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >################################################################ >To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: >To subscribe: SUBSCRIBE TechNet <your full name> >To unsubscribe: SIGNOFF TechNet >################################################################ >Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. >For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 >################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################