HI Mike, We specify dams on all fine pitch. I can't live with out it. If you don't get it on fine pitch you better have an automated stencil for registration. Otherwise it is solder bridge city. Specifying LPI for Soldermask will work fine. You may get few broken dams but that is the price you pay for having 14mil pads. Hector Valladares Honeywell -SASSO Production Staff Engineer 727.539.3683 voice 727.539.4469 Fax [log in to unmask] -----Original Message----- From: McMonagle, Michael R. [SMTP:[log in to unmask]] Sent: Saturday, August 22, 1998 8:48 AM To: [log in to unmask] Subject: Re: [TN] Stencils for Gold Boards -Reply 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 ################################################################ ################################################################ 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 ################################################################