At 12:00 AM 12/9/01 -0600, you wrote: >Date: Sun, 9 Dec 2001 00:00:11 -0600 >Reply-To: TechNet <[log in to unmask]> >Sender: TechNet <[log in to unmask]> >From: Automatic digest processor <[log in to unmask]> >Subject: TechNet Digest - 7 Dec 2001 to 8 Dec 2001 (#2001-766) >To: Recipients of TechNet digests <[log in to unmask]> > >There are 2 messages totalling 54 lines in this issue. > >Topics of the day: > > 1. BGA Rework Equipment > 2. Plating and Resin Recession > >--------------------------------------------------------------------------- >------ >Technet Mail List provided as a free service by IPC using LISTSERV 1.8d >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF Technet >To temporarily halt delivery of Technet send the following message: SET >Technet NOMAIL >Search previous postings at: www.ipc.org > On-Line Resources & Databases > >E-mail Archives >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional >information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 >ext.5315 >--------------------------------------------------------------------------- >------ >Date: Sat, 8 Dec 2001 05:23:36 -0600 >From: Earl Moon <[log in to unmask]> >Subject: Re: BGA Rework Equipment > >I really echo Warren's message. When first developing HP's BGA rework >process, using SRT, it took three months to get everything almost right. >Then, there were surprises needing rectification. It never really ended as >new boards and components were designed and built plus CPI. > >The process first must be developed. It must be transferred to manufacturing >including all procedures for everyone and all parts involved, or those >perceived to be, it must be validated for each part on each board type, and >operators must be trained for each shift. Though most all operators great at >their jobs, some definitely caught on quicker and did consistently better >jobs than others. > >Profiles alone can take much development time, and they're long themselves, >no matter the paste or original assembly profile. Parts must be removed and >sites cleaned and touched up and thoroughly inspected. A costly supply of >nozzles must be bought as well. Micro stencils must be purchased and >processes developed for their use. Part replacement and reflow processes >must be right on. X-ray inspection is a must for rework, as it is for >prototypes, before final test, and on it goes. > >This is a good one to "farm out." I think you already knew this or are an >excellent rework engineer yourself. > >MoonMan >Date: Sat, 8 Dec 2001 17:45:23 EST >From: Werner Engelmaier <[log in to unmask]> >Subject: Re: Plating and Resin Recession >MIME-Version: 1.0 >Content-Type: text/plain; charset="US-ASCII" >Content-Transfer-Encoding: 7bit > >Hi Roger, >Thicker copper deposits have indeed greater (but not better) elongation >values than thinner deposits. This, however, does not mean that thinner >deposits have less ductility; the lower elongation value is an artifact of >using a test method which is inappropriate for sample geometries like plated >copper foils. Elongation tests work well for specimen for circular and square >cross-section; foil specimen have a cross-sectional aspect ratio of 500 to >1000, which creates this type of artifact. >This is the reason test methods specific for foils (ASTM E 796 "Standard Test >Method for Ductility Testing of Metallic Foil," IPC-TM-650, TM 2.4.2.1 >"Flexural Fatigue and Ductility, Foil" ) were developed. These test methods >show there is no difference in ductility for thin or thick foils from the >same batch. Hi, I will be back on 12/17/01. Regards, Jong