I am with Patty, it has been around for a long time. I saw my first pink ring in 1965 when we switched from bare copper to oxide treat to improve adhesion. Of course, I did not see it by looking at the board because it was not on the the layer you saw when looking into the board. You had to make a horizontal microsection from the inside of the board in order to see it. Pink ring to various degrees existed on most boards from the 60 until the 1980's and someone decided to use a new process called "cap foil" and pink ring became apparent to the casual observer. Seaching for a something to call this newly discovered defect, we called it "delamination" and were able to scrap a good many circuit board for this reason. Then the Thermal Zone concept came into existence and a delamination in Zone A was acceptable. How can we scrap the board using the Zone concept, a big problem!! So the argument goes on. To my best knowledge there has been no studies or reports that show that pink ring without wedge voids causes any functional problem or that it will cause delamination. There are many reports that show that pink ring without wedge voids is a benign defect and even though it looks ugly, it is not a functional defect. Perhaps to settle the argument, we should go back to hiding the oxide layer or always use reduced oxide to satisfy the purists. Invisible pink ring often occurs on reduced oxide, but appears only as a circular stain around the hole and is not visible from the surface. You must make a careful horizontal microsection in order to detect it, so it is acceptable. I heartily agree with Patty that the processes used in lamination, drillling, oxiding etc. will increase/decrease pink ring, but did we improve the board or its reliability.. Maybe the next 30 years will tell. Phil Hinton *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************