I have a board with a power trace that's 2.75 in [70mm] long and 40 mils [1mm] wide.  The trace goes between two plated through-holes.  It carries 0.5A at room temperature.  I've never seen any problems with the board design.

On a particular board, however, this trace is intermittently open.  I looks fine under the microscope, yet it is clearly open.  I scraped away some of the soldermask and worked out which half of the trace had the problem.  I know the problem must be where the trace comes into the PTH's pad, but I can see nothing.  So I scraped away the soldermask over the trace where it comes into the PTH's pad and tinned it with solder.  The open went away.

I've worked with boards with PTHs for 11 years, and I've never seen such a thing.  Has anyone seen a large trace fail open with no outward sign?

---------------------------------------------------------------------------------
DesignerCouncil 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 DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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
---------------------------------------------------------------------------------