Dear XANSYS community, I’m writing to discuss something that has come to my attention recently. During my search of research papers in the area of modeling and simulations of electronic assemblies, I have found a recent article published in a ultra reputable journal in the field. No need to mention specifics. In this paper, the authors have done creep tests on a new technology bonding method and they’ve extracted Anand’s creep model coefficients (the famous 9 parameters) using nonlinear curve fitting process. Interestingly, many values of such constants are reported to be “negative” and some other parameters do not match with the conditions of Anand’s law. What makes it even more interesting is that the authors didn’t comment at all on such weird observations. Additionally, no FEA simulations using such material model were provided. In my knowledge, all Anand’s parameters have to be positive values and one specific parameter (a - the strain rate sensitivity coefficient of the hardening/softening process) is equal to or greater than one. I triple checked! Which comes to my conclusion is that the parameters provided in that paper are questionable? Right? Am I missing something? I would love to hear some thoughts on this. Best Regards, MG

I quickly checked limited amount of material data we have from our “Solder Joint Reliability” class notes and I can confirm that all Anand constants are positive values. In full disclosure, we have never done creep tests; just went through papers published on this. In the past, we have noticed one inconsistency in one of the published papers that one of Anand constants was way off (it was not a negative number but orders of magnitude off); was it a typo or was it done on purpose? We just moved on and used data from other published papers… From: Mohammad Gharaibeh via Xansys <xansys-temp@list.xansys.org> Date: Saturday, August 19, 2023 at 2:47 AM To: XANSYS Mailing List Home <xansys-temp@list.xansys.org> Cc: Mohammad Gharaibeh <mgharai1@binghamton.edu> Subject: [Xansys] Negative values and f Anand’s parameters? Dear XANSYS community, I’m writing to discuss something that has come to my attention recently. During my search of research papers in the area of modeling and simulations of electronic assemblies, I have found a recent article published in a ultra reputable journal in the field. No need to mention specifics. In this paper, the authors have done creep tests on a new technology bonding method and they’ve extracted Anand’s creep model coefficients (the famous 9 parameters) using nonlinear curve fitting process. Interestingly, many values of such constants are reported to be “negative” and some other parameters do not match with the conditions of Anand’s law. What makes it even more interesting is that the authors didn’t comment at all on such weird observations. Additionally, no FEA simulations using such material model were provided. In my knowledge, all Anand’s parameters have to be positive values and one specific parameter (a - the strain rate sensitivity coefficient of the hardening/softening process) is equal to or greater than one. I triple checked! Which comes to my conclusion is that the parameters provided in that paper are questionable? Right? Am I missing something? I would love to hear some thoughts on this. Best Regards, MG _______________________________________________ Xansys mailing list -- xansys-temp@list.xansys.org To unsubscribe send an email to xansys-temp-leave@list.xansys.org If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode which will send a single email per day. Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list

Thanks, Metin, for the response. First of all, I have to declare that I am not trying to pick up a fight or attack anyone or anything. Just trying to have a scientific discussion with the experts here. Back to the topic, in the paper I was referring to, there were “four” parameters with negative values. So I would not just assume this was a typo. I cannot say it was on purpose either. The confusion here is that how could this have slipped off the reviewers hands in such a high-profile journal? Again, a little discussion on the negative values would’ve been helpful to further justify. ANSYS Theory Manual, In Anand Option section, explicitly mentions that all the parameters have to be positive and, as stated earlier, the “a” coefficient is equal to or greater than 1. Of course I’ll be moving on from this and literature is flooded with solder joints creep models. It is Not the end of the world! Just something I thought might of interest for the scientific community. Kind Regards, Mohammad On Saturday, August 19, 2023, Metin Ozen <metin@ozeninc.com> wrote: > I quickly checked limited amount of material data we have from our “Solder > Joint Reliability” class notes and I can confirm that all Anand constants > are positive values. In full disclosure, we have never done creep tests; > just went through papers published on this. > > > > In the past, we have noticed one inconsistency in one of the published > papers that one of Anand constants was way off (it was not a negative > number but orders of magnitude off); was it a typo or was it done on > purpose? We just moved on and used data from other published papers… > > > > > > *From: *Mohammad Gharaibeh via Xansys <xansys-temp@list.xansys.org> > *Date: *Saturday, August 19, 2023 at 2:47 AM > *To: *XANSYS Mailing List Home <xansys-temp@list.xansys.org> > *Cc: *Mohammad Gharaibeh <mgharai1@binghamton.edu> > *Subject: *[Xansys] Negative values and f Anand’s parameters? > > Dear XANSYS community, > > I’m writing to discuss something that has come to my attention recently. > > During my search of research papers in the area of modeling and simulations > of electronic assemblies, I have found a recent article published in a > ultra reputable journal in the field. No need to mention specifics. > > In this paper, the authors have done creep tests on a new technology > bonding method and they’ve extracted Anand’s creep model coefficients (the > famous 9 parameters) using nonlinear curve fitting process. Interestingly, > many values of such constants are reported to be “negative” and some other > parameters do not match with the conditions of Anand’s law. What makes it > even more interesting is that the authors didn’t comment at all on such > weird observations. Additionally, no FEA simulations using such material > model were provided. > > In my knowledge, all Anand’s parameters have to be positive values and one > specific parameter (a - the strain rate sensitivity coefficient of the > hardening/softening process) is equal to or greater than one. I triple > checked! > > Which comes to my conclusion is that the parameters provided in that paper > are questionable? Right? > > Am I missing something? I would love to hear some thoughts on this. > > Best Regards, > MG > _______________________________________________ > Xansys mailing list -- xansys-temp@list.xansys.org > To unsubscribe send an email to xansys-temp-leave@list.xansys.org > If you are receiving too many emails from XANSYS please consider changing > account settings to Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list > -- ===================================== Mohammad A Gharaibeh, Ph.D. Associate Professor Department of Mechanical Engineering The Hashemite University P.O. Box 330127 Zarqa, 13133, Jordan Tel: +962 - 5 - 390 3333 Ext. 4771 Fax: +962 - 5 - 382 6348 =====================================