Thanks to everyone for the prompt responses, it validated my concerns (I was right, nyah, nyah, nyah!). We're getting another stencil burned right now with 12mil aps, the 1:1 stencil originally specd was a disaster, 4-6 bridges every board. Now to another topic: What are your experiences with mask dams/webbing and fine pitch? In previous lives, I tried to specify mask between pads on 25mil and under. This seemed to help minimize bridging potential. However, I am now dealing with people higher up that have had bad experiences with this practice, and I want to bring about a dialog to pursue some process experiments. Step up to the pulpit and tell it like it is, brother (or sister). Amen! Mike McMonagle PCA Process Engineering Supervisor K*Tec Electronics 1111 Gillingham Lane Sugar Land, TX 77478 (281) 243-5639 Phone (281) 243-5539 Fax [log in to unmask] > -----Original Message----- > From: Stephen R. Gregory [SMTP:[log in to unmask]] > Sent: Friday, August 21, 1998 6:14 PM > To: [log in to unmask] > Subject: Re: [TN] Stencils for Gold Boards -Reply > > In a message dated 8/21/98 2:44:24 PM Pacific Daylight Time, > [log in to unmask] > writes: > > << Just one note, all reflowed solder joints have dull or > gray-looking > appearance. That's normal. Gold diffuses into melting solder causing > dull or > gray-looking solder joints. >> > > Hi Mike! > > Matthew gives you good advice about your apertures. About his > comment of > the solder joints looking dull and grainy on gold boards, I got a tip > for you > to make em' look better, use a 2% silver solder with them (62/36/2). > It lowers > the melting temp a little...I think liquidous is 179 C. vs. 183 C. > with a > 63/37, and that ain't all that different, it's still eutectic, and it > shouldn't cost much different (if you get charged anything different > at all) > from a regular ol' 63/37. > > I worked at a memory company a couple of years ago where we had > quite a > few gold boards and that's what we used and our vendor charged us the > same > price...I'm not a metallurgist, so I can't tell you PRECISELY why the > joints > look better with a 2% silver, but they do, I'm not pulling your leg > either... > > I do remember reading something quite a while back that there > was a > mistaken belief floating around that if you used silver in your solder > that it > would prevent the leeching of the gold into the joints during > reflow...something about the silver in the solder being a noble metal > like > gold is, raises the percentage of noble metal in the solder joint > which > reduces the leeching of the gold. We all know now that's not true, but > I'm > thinking maybe where that belief may have gotten started was > difference in the > solder joint appearance...someone may have thought back then that the > addition > of silver really did stop the gold leeching. > > -Steve Gregory- > > ################################################################ > 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 ################################################################ ################################################################ 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 ################################################################