Matthew, Yes, other adhesive systems (epoxy and some of the FR formulations) could help. Coverfilm bond strength tests could help you to discriminate between the relative rankings of performance, but the absolute values measured may not have any direct meaning to your application. (The standard tests often fail to discriminate for the particular failure mode you're trying to deal with.) There are a good many things that could cause uneven discoloration, and others have suggested the key bad ones. However, some sources of discoloration are quite meaningless in terms of physical performance, so unless they're falling apart don't give up on your circuits too easily. You may be exceeding the rated capabilities of the coverfilm adhesive. What temperature was your 2.5 hr bake? What temperatures were the reflow cycles? Acrylics in particular are prone to oxidation and embrittlement leading to loss of bond strength with exposure to time/temperature. In the process of making the 6 layer rigid flex your supplier may have used up most of the adhesive's useful temperature resistance. Acrylics also provide some of the poorest barriers to moisture transmission. My only addition to Dr. Sallo's review of Sputtered vs. Cast would be the DuPont AP products, and some very thin cast products that Rogers was doing for one special customer. Andy Magee Flex Guru - Consulting [log in to unmask] (937) 435-3629 Matthew wrote, We're currently using adhesiveless base material on the parts due to some low yield problems we'd seen in the past. Unfortunately, the delamination we're seeing is coverlay to copper where we're using the acrylic adhesive. Does anyone have experience with epoxys or other adhesives for that component? As for the tweezer method, that's similar to what we've been doing as a check; I feel pretty good about the method, but I'm worried about the possibility of this discoloration, even if it doesn't give me the tactile delam feedback, having some problems later in life. I worried that even the C-SAM, while it can verify the parts as-is, won't necessarily tell me if I'll see any future problems (or if it's ok now, will it be ok in the future?). Does testing the bond strength between the cover and the copper help? This is something of a separate thread, but for adhesiveless flex materials, is there any practical functional difference between cast polyimide and sputtered copper (/11 and /12 I think). Is it a difference I should worry about when specifying materials? Thanks for the information so far! Matt Matthew Sanders PCB/Metal Procurement Engineer, Trimble Navigation Ltd. [log in to unmask] Phone: (408) 481-7817 Fax: (408) 481-8590 ################################################################ 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 ################################################################ ################################################################ 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 ################################################################