Hi Dave and Werner: Thanks for your clarifications re. the standards issue. All right, no "BLIND" implementation. But is "a well-informed" one more appropriate? I'd say MIL-STD-2000 did not make it because no one could say confidently why a thruhole with 60% of the pad wetted with solder should be any worse than the one with solder all around its periphery. I am only citing a single instance where cost and cycle time could have been reduced with some information, but was not. My stand is this: If reliability criteria have been so well understood as to come up with D-279, then why arent they incorporated into the IPC-610/J-STD-001 more obviously? Let us face the fact that these documents are being used extensively as guidelines for inspection. A handbook is being prepared about how to interpret IPC-610, and lots of inspectors have attended short courses at EMPF about the guidelines. When a work such as the 610 or 001 is brought into mainstream manufacturing, it is natural for the individuals using it, to assume that it has been carefully documented and to place some faith in it. To tell them that it is upto their abilities and resources to determine whether the guideline is applicable to them is only unfair. Companies are often faced with this question: How do we ensure that the manufactured parts at least meet the expected operating conditions? This then mushrooms into an argument of conservativeness vs. quality. Another real issue is: With rapid design changes and shorter product lifecycles becoming the norm, are we spending a lot of money by being over-conservative? About the only things that everyone agrees upon are obvious defects such as bridging, tombstoning, misalignment,... The real culprits that cost money to verify and are the bigger headaches are those that affect reliability and field performance. Every company can come out with nice shiny joints that conform to guidelines (well not every one) but are they reliable? This is the determining factor for product superiority in the current marketplace. Hence, we must not neglect it. Every time someone out there asks a question about how to judge conformance to specifications, it indicates lack of adequate information. Maybe that's why TechNet exists, but there has to be a better way. I hope I have made the case for reliable solder joints quite clearly. In the following para, I have included some of my thoughts about how to meld this into the guidelines. This is what I personally would like to see happening and I am eager to assist in whatever way I can. Regardless of the particular geometry (GullWing, J-Lead, Leadless, BGA ...) and loading conditions, the solder fillet remains the only sign of electrical and mechanical contact. If the post-reflow appearance of the solder joint can be correlated with post-reliability testing results, there will be a solid case for the guidelines. If this has been incorporated into the current guidelines, then it is clear that the definition of Assembly Classes is deficient. The particular range of reliability conditions that a guideline applies to must be specified (Temperature cycling -20 to 55, 75% humidity, etc.) so that the users of the guideline can obtain a better idea. Manufacturing practices can be stated to be viable only to the extent that product lifecycle considerations can be met. This of course assumes that the design is flawless. Now how often does one see that?!!! So some confidence limits need to be placed on the guideline. I am not disparaging the excellent cooperation that has produced both IPC-610 and J-STD-001. I am only trying to say my 2 cents worth to improve its applicability. I am sure that Solderability, because of its very definition, will come to be better documented than inspection criteria. And I am thankful that this is not a flamethrowing match. Best Regards, Vijay Sankaran Research Associate Center for Integrated Electronics and Electronics Manufacturing Rensselaer Polytechnic Institute Troy, NY 12180 Ph: (518) 276-2721 Fax:(518) 276-2990 *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************