Hi Sarah, I would like to ask the following questions on separation problem: 1) what is the difference between IL separation and post separation? There is no difference - post separation is a term used to describe the more proper term - inner layer separation. Sometimes you will hear it referred to as T Joint separation too. 2) what causes the occurrence of such kind of defect? There are numerous causes depending upon where the separation occurs. Can you determine if it is between electroless and inner layer, within electroless, or between electroless and electrolytic? At one time when I was building boards - we had it every fall when our ambient rinse tanks became cooler than they were in the summer. Heated rinses made it go away. Once you determine where the separation is located, we can help with the processes that are involved. 3) how can we prevent this type of problem from occurring? First you have to determine what step in the process is causing it. 4) at what layer does this problem usually occur? Traditionally it appears at layers 2 and N-1, due to their seeing more movement during thermal stress testing and any other thermal excursion. 5) how can you distiguish separation from resin smear? When you look at microsections the separation is filled with resin and not a "hole" that is present from actual separation. This is sometimes easier to see with polarized light. If you suspect drill smear, you can run your board through an oxide process immediately after desmear and then examine the inner layers. Copper inner layers will be black, but any smear will not be coated with oxide. Hope this helps to get you started on solving the problem Susan Mansilla Robisan Lab ################################################################ 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 ################################################################