Hi Doug, See my responses below: >>Steve, >>I have not used that specific material before, but have worked with 2-part >>systems. A few questions and observations: >>1. What did you mix the material with? Metal spatula (good) or popscicle >>stick (bad)? Answer: I mixed it with a plastic spatula >>2. How well did you scrape the sides of the container? Was it a clean >>plastic mixing cup (good) or wax-coated Dixie cup (bad)? Answer: I thought I scraped the sides pretty good. It was a clean plastic mixing cup, just a regular kitchen mixing cup with graduations on the sides. >>3. Did you bake out the potted assemblies first? Answer: No I did not. In retrospect I should have... >>4. Was there a primer involved? Answer: No primer. >>5. What kinds of "schmutz" may be on the assembly that may poison the >>cure reaction? Urethanes don't like water. Answer: I thought the boards were clean. I learned afterwards that there was some no-clean rework done to a programmed part (it was removed and replaced), although I didn't see any residues. >>6. Does the manufacturer recommend a rest time before potting? Degassing >>before potting? Answer: I didn't see any rest time or degassing recommendations in the datasheet. >>You might want to pick up IPC-HDBK-850, The Potting and Encapsulation >>Handbook for lots of good information. Yep, will ask that we get the Handbook. I called Epic and talked to them about what happened, and they told me that I should mix by weight to be more accurate. So as a test of the material, I did that. I mixed 300-grams of part A to 129-grams of part B (100:43 ratio per the datasheet). Mixed it the same way I did last week, then poured the material into two containers. This time I did the alternate oven cure of 65 C. for 1 to 1.5 hours. It turned out beautiful. Smooth, with no bubbles except for some very tiny ones around the edges of the container. I am at a loss as to why I had the results that I did last week. So frustrating... Steve From: stephen gregory <[log in to unmask]> To: <[log in to unmask]> Date: 07/22/2013 01:46 PM Subject: [TN] Epic Resins S7144A 2-part polyurethane potting material Sent by: TechNet <[log in to unmask]> Hi All, Have any of you used Epic Resins S7144A 2-part polyurethane potting material? I tried to last week, and pretty much made a mess. Followed the datasheet and mixed it in the volume ratio of 3-parts part-A (300-cc) to 1-part part-B (100-cc). I mixed more material than I actually needed. I'm mixing it by hand because we don't have a MMD system. I thought I had mixed everything thoroughly (4-5 minutes). I determined ahead of time how much material would be needed for each unit (35-cc's). After mixing, I drew the material into a 60-cc syringe and dispensed 35-cc into each case. I let it room cure (24-30 hours). I did 4-units and each one of them had a different result, from swelling and bubbling of the material completely out of the case, to little or no cure. I'm at a loss as to why that happened. Just wondering if any of you have ever used the material and can give me some pointers. Thanks guys, Steve ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________