Soldermask thickness and dielectric are of a tertiary level of effect in the impedance calculation. Therefore effect of soldermask, especially LPI soldermask, is negligible. The quick rule of thumb is that it adds about 1-ohm to the impedance, far less than the 10-20% tolerance that is generally specified for controlled impedances. This does not mean that its effect should be ignored in tight designs. As to Steve's original problem of how to deal with the boards he has - hand assembly is probably his best choice. From what I see in his photo, he is not in as bad of shape as he could be; I worked with one RF Engineer who demanded no thermal relief at ground connections, No soldermask and HASL finish talk about a nightmare for the tech's. Jeffrey A. McGlaughlin, C.I.D. Sr. PCB Designer Battelle Memorial Institute Columbus Ohio [log in to unmask] -----Original Message----- From: Beerman, Dennis [mailto:[log in to unmask]] Sent: Thursday, January 11, 2001 11:58 AM To: [log in to unmask] Subject: Re: [TN] RF Surface mount... James, Are you saying that the addition of a soldermask has no affect on a controlled impedance microstrip? ---------- From: Terveen, James @ NARDAEAST [SMTP:[log in to unmask]] Sent: Thursday, January 11, 2001 11:56 AM To: [log in to unmask] Subject: Re: [TN] RF Surface mount... Steve, I do alot of this kind of boards seeing that we are an RF house. For some reason the design guys seem to think that the mask will effect the RF performance of the boards, I have yet to see that happen when we have changed over to an all soldermasked board and some of our boards go up to 26 GHz. From what I saw on your picture you will probably have some tomestoning but not nearly as much as you may think. The problem you have is they are trying to go to ground on the components and those are the areas that may cause you the most problem But I don't think it will be nearly as bad as you think it is going to be. Good Luck -----Original Message----- From: Stephen R. Gregory [mailto:[log in to unmask]] Sent: Thursday, January 11, 2001 11:00 AM To: [log in to unmask] Subject: Re: [TN] RF Surface mount... In a message dated 01/11/2001 9:49:00 AM Central Standard Time, [log in to unmask] writes: > Steve, > > Ina very past life we produced a product similar. We were able to control > the solder running and maintain the solder tension at the pad site by having > the trace necked down considerably (bare minimum width) to force and create > as large a solder dam as possible. > > Kathy Hi Kathy! It looks like they've done that with some of the pads but not with all of them. You can see what I mean by looking at a picture I've taken of a section of the PCB. Go to: http://www.driveway.com/share?sid=4eced0a4.94f42&name=Pictures&view=3 There you'll see the footprint for 4 components, a large cap, two 1206 parts, and a 0805 part. I'm not sure if they necked down the traces to help with soldering, but I still think I'm going to have a lot of problems if I try to print paste and reflow...don't you? Thanks! -Steve Gregory- ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------