Issue link: https://iconnect007.uberflip.com/i/1498723
28 DESIGN007 MAGAZINE I MAY 2023 the hamburger the right way and use the right materials to build the hamburger so it gives everybody what they want. ere are a lot of variables in circuit board manufacturing. We have this long-time phi- losophy about dimensioning, tolerancing, and specification of any part. You specify what you want to end up with, or for the end-type per- formance, but you don't tell anybody how to do it, or too much about how to make it right. If we can be as general as possible and allow our stakeholders to have a say and dial in the mate- rials to achieve the performance specification that we've outlined, we'll be set up for flexible cost savings. Shaughnessy: I like that; let the stakeholders have a say. Holden: Unfortunately, when you select compo- nents, there's no informa- tion about the manufac- turing repercussions of selecting this component. The design engineer selects components. If he starts mix- ing technologies—through-hole, surface mount, and bottom-leaded components, for instance—the mixture makes it really difficult to say, "Do this and don't do that," because of the permutations and combinations. That's why it's best to communicate early on with the manufacturer. Exactly. If we define our stackups with what I call the recipe approach, the fabricator must put together stackup ingredients like a recipe. ey will need to put together core layers and prepreg the way the PCB designer shows it in the stackup recipe when it might not be appro- priate at all. ey should untie the supplier's hands to be able to use prepregs or whatever they need to meet the performance and thick- ness requirements of the board. Holden: Many don't appreciate that quick- turn prototype companies make their money off their knowledge; they can build what you specify in record time. They're the Burger Kings of the industry: Have it your way. They'll build it any way you want. That does not necessarily mean that the board is suitable for high-volume production. Designers who go offshore spend much more time talking to suppliers and assemblers. If there's some secret that makes the proto- types work, that had better be incorporated somehow into the final specifications. Knowing the terms and the anatomy of a slash sheet is a good thing, but specifying it on a drawing is another. We must know how to specify, to know the language of the industry for appropriate, effective specification. Shaughnessy: Some design- ers have said that they'd love some sort of material guidelines that are final application-sortable, where you'd say, "Okay, I'm working in automo- tive," then it would give you a list of each type of material that fits under that. Would a one-stop shop approach be helpful? Yes, in one sense, but dangerous from the standpoint of taking that product out of proto- type and launching it into production. "Here's the slash sheet, it has specs here, and that's all there is to it." What has been suggested is that these slash sheets were never intended for designers. at's a good thing to hang our hat on. We do a lot of daisy-chaining. We say, "Inspect our acceptability requirements for IPC-A- 600," and that says the supplier has to build and inspect it to IPC-A-600. at one sentence gets us the specification that covers everything. There are a lot of variables in circuit board manufacturing. We have this long- time philosophy about dimensioning, tolerancing, and specification of any part.