Not entirely sure I understand your question, Here's my take. If the component is overhanging pad then the actual contact area pad to component is going to be less with solder but pretty much the same for adhesive (the solder will only bond metal to metallisation, but the adhesive will stick to whatever it is in contact with). However the lap sheer of Ag adhesives is (roughly) only about a half that of solder, but this may not be so significant if you have fillets as then you have increased bond area and the bond is also in tensile, Of course if you have a TCE mismatch then the extra compliance of solder is important as this will accommodate it better than most adhesives as these are more rigid, but you could have a flexibilised adhesive compared to a very thin solder bondline which changes things somewhat and the stress may be in peel, of course this is at room temperature at higher temperatures the solder will soften but the adhesive won't till it reaches Tg, but also .... I think you get the point. Good luck on modelling: In this respect don't forget that Ag adhesives are composites, so the properties given in data sheets [which are based on classical tests on bulk samples], may not actually reflect the reality of the material when used in thin bondlines and to/across interfaces. For these sorts of reasons most adhesive applications of this type are application specific and subject to actual testing. Regards Mike Fenner Indium Corporation T: + 44 1908 580 400 M: + 44 7810 526 317 F: + 44 1908 580 411 E: [log in to unmask] W: www.indium.com Pb-free: www.Pb-Free.com -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Doug Pauls Sent: Tuesday, December 09, 2003 8:14 PM To: [log in to unmask] Subject: [TN] Adhesive strength vs overhang Good afternoon all, Internally, we are having discussions on the amount of allowable overhang of passive SMT components (R and C). Our specifications are based on solder joint connections and the solder specifications are not in question. We have an application where a silver filled adhesive is used to make the connection between SMT metalization and mounting pad. The solder joint requirements were applied to these adhesive joints and I am wondering as to the validity of this. The adhesive is epoxy based and, in my mind, more rigid than solder. I think we are unnecessarily rejecting parts that are acceptable. So, before I go off and do a complex designed experiment, I thought I would check with the Technet crowd first. Do you know of any studies that show the adhesive force (e.g. pull strength) vs. the degree of pad overhang? 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