This is very good input. Thanks, Earl Moon ----- Original Message ----- From: "Dave Chapman" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, July 02, 2002 12:40 PM Subject: Re: [TN] Shelf life of Immersion Silver Fabs > Mac Dermids processing guide speaks specifically about packaging > requirements. > > Our company just issued instructions to our boardhouses as to packaging > for Alternate finish boards. Boards must be packaged in lots of 25 > generally, although 10 to a pack is acceptable if they are larger boards > and more than 25 if they are smaller than 2"X 2". This is standard practice > at our houses and we assume at most others. We dont want to open every bag > of boards for inspection so after QC checks a few boards at incoming we > will reseal them. This includes boardhouse over runs left on their shelves > for planned release shipments. > > the board house must put a paper date label on the outside of all packages. > > The top and bottom board in the package must be covered by sulphur free > paper. (Since Immersion Silver finish is below the board surface we are not > worried about surface scratches) Plastic will tarnish boards surface. > > I have 30 Silver boards in my desk wrapped in paper. They have been there > over 1 year. The top and bottom boards are very tarnsihed but all the rest > are fine. > > Packages must be vacumm sealed. ( if house has those capabilities otherwise > we will seal them at receipt) > > Another caveat is if you have to deal with a boardhouse which sends the > boards out for processing. Legend print is recommended before Immersion > Silver is applied since chemicals or heat used in screening can cause > tarnish, staining and unsolders unless they are using a UV ink. > > No dessicant is to be inserted inside vacuum sealed packs but is allowable > inside packing boxes. > > The secret to success is to treat all boards as if they are Silver > Immersion, this avoids tricky document changes and special handilng > procedures on the assembly floor. Operators should not be touching any > boards surface with bare hands, washing should be kept to a minimum on All > boards. > > We are having a very positive experience with Immersion Silver transition > from HASL. 15 assemblies which were problems before are now switched over. > All BGA boards and anything with 20 mil fine pitch is automatically Silver > Immersion. We use both Alpha Level and Mac Dermid processed boards. > > Aperture selections of stencils for fine pitch is where we are > concentrating now, since you are starting with 50% less solder you need to > increase the stencil aperture size but on fine pitch with a 1:1 ratio you > have shorts on everything less than 20 mil spacing. Better to get shorts > than opens but we want to reach the perfect balance. If anybody is already > there would appreciate the feedback, if not we will post it when we get > there. > Dave Chapman > Circuit Service > > -------------------------------------------------------------------------- ------- > 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 e-mail to [log in to unmask]: SET Technet NOMAIL > To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/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 > -------------------------------------------------------------------------- ------- > --------------------------------------------------------------------------------- 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 e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 ---------------------------------------------------------------------------------