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28 SMT007 MAGAZINE I JULY 2019 In my last column, I discussed realistic goals to aim for regarding defect levels. I also men- tioned, but it is worth repeating, that it may be unrealistic to have zero defect in products right after reflow, but we want zero defect in products we ship to the customer. That is why we spend so much time and money on inspec- tion, test, and repair even though they are non- value added process steps, but they are neces- sary steps since you don't want the customers to discover those defects. As to the question raised in this column, would I prefer shorts or opens in my products? Neither, thank you. But if I do have to choose, I would choose a more desirable defect, if there is such a thing. But what is a desirable defect? A defect that would never escape inspection and test and would be caught before shipping the product to the customer. Before I answer this question, let me briefly review industry stan - dards on defects and major types of defects that really matter in the functioning of a product. Industry Standards and Major Types of Defects There are three major types of standards in our industry: IPC, EIA, and J-STD. Each one has a different focus, reasoning, and target audience. Having been deeply involved with various standards, chairing many of them over the years, and still chairing many others, let us save this topic for future columns. For now, I will focus on two standards that deal with acceptance criteria for defects. IPC-610 is a thick and widely purchased IPC standard that specifies acceptance criteria for all types of defects with color photos and very little text. It is easy to read and follow and is primarily targeted at inspectors and operators working on the SMT line. Would You Prefer Shorts or Opens in Your Products? SMT Solver Feature Column by Ray Prasad, RAY PRASAD CONSULTANCY GROUP

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