Genny, When I used deal with creapage and clearance requirements for Telecom network voltage application. I believe UL 1950 spec stated that when you had an isolated conductor between two conductors that needed a certain separation you added the spaces on each side of the isolated conductor. So in your case if the sum of the two spaces is greater than .13mm so the minimum clearance is not violated. The rational being that arcing occurs based on the potential difference between the conductors on each side of the gap. Think of the two gaps as series resistors. By having the solder ball in the middle you now have a greater chance of something else coming along or growing off one pad and can now cause a short faster since there is less gap to fill. I guess it depends on your area of concern and I don't know what it was for the IPC spec. Jim Verrette Senior Electrical Engineer ------------------------------ Date: Tue, 9 Sep 2008 09:13:42 -0600 From: Genny Gibbard <[log in to unmask]> Subject: Solder balls and minimum electrical clearance I posted a question a couple months ago about solderballs. The debate is still happening here. I thought I would post a more specific question regarding how to interpret the standards. Consider a low voltage situation, where minimum electrical clearance is 0.13mm according to Table 6-1 in IPC-2221.=20 IPC-A-610 states for acceptable: Solderballs are entrapped/encapsulated and do not violate minimum electrical clearance. Components are so small now, that solder fines are starting to come into question when they would probably have never been noticed a few years ago. If a solderball is entrapped under a component between two pads, and the sum of the distance from pad to ball and ball to next pad is greater than 0.13mm, but each individual distance (pad to ball) is less than 0.13mm - does this violate minimum electrical clearance? The solderball is not connected to anything. My thought this is a violation, because the solderball is sort of like a stepping stone in the middle of the stream, that would make arcing that much easier. But I am wondering if my logic is flawed? An arc still needs to cover the whole span, and the solder ball isn't electrically connected or contributing to the voltage difference . These are usually solder fines that aren't moving. If one were to somehow get loose and move toward one pad, though, the remaining distance would not be a failure. It is just when they are trapped in the middle between two pads that each individual distance is a failure. If the stepping stone idea is correct, we have a lot of solder fines to rework. So I am hoping it is incorrect... But we will do what is right. Your assistance in interpreting the standards is much appreciated. Genny=20 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------