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Larger Stencil Apertures and Type 4 Paste
Board Talk
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TranscriptPhil Welcome to Board Talk with Jim Hall and Phil Zarrow of ITM Consulting, known to you here in Board Talk land as the Assembly Brothers. And today we're coming to you from the ITM Consulting Auxiliary Failure Analysis room which is located in the back of Rusty's Roadside Cabaret in Greensboro, Tennessee. Jim, what's our question for today? Jim Well it's a materials question, Phil. It comes from J.V. What is your experience with larger size apertures and type four solder paste and how does it affect solder joints for non-collapsible BGA and CGA type solder joints? Phil Okay, fair question. I'll start off by saying that you know from a com site is of course you don't want to use a type four paste unless you have to. You know there are apertures on the board, you know on the stencil that require it just because of the type four does have a little bit more propensity to oxidize because of the small particles than say a type three and it costs more money. But aside from that, Jim, it's becoming more and more common, isn't it? Jim Absolutely and with a propensity of smaller components, 0.5 millimeter, 0.4 millimeter area array packages, type four is becoming almost the standard. And I think you're out of touch with current technology, Phil. I think the oxidation issues have been long handled in the newer type four pastes. That certainly was a concern back you know eons ago when you and I were cutting our teeth in the industry. But now the advances in modern flux technologies in today's paste with the type fours being so common, I think have virtually eliminated all those problems. I don't see any issues with using them with larger apertures. I mean think about it, most boards that are being built today are some combination of the larger apertures and the small apertures for the very fine-pitched components. Likewise I wouldn't see it having any problem for the non-collapsible ball grid or column grid array type of solder joints. All modern pastes are being formulated with very robust fluxes today. But nonetheless you should evaluate any paste you use before you put it in your process just to make absolutely certain it's compatible with what you're trying to do. And you know, Phil, with the driving force of the handheld market pushing us to even 0.3 millimeter packages and chip scale packages and QFNs and what have you, people are talking more commonly about type five powders, type five pastes which were almost unheard of you know four or five years ago. Now type four is almost common and of course if you get the special variations within those of the type 4.5 or type 3.5 or 5.5 where the manufacturers have created a more limited particle distribution within the specification for those IPC types. But, it's a good question. As you said type four is typically designed for small apertures but with modern flux formulations you shouldn't have any problem with any of your other types of solder joints. But it still is going to be more expensive because of the greater processing required to produce the smaller powders. I don't see that as ever changing. Phil Right and I would only add to that like with any solder paste and as my brother Jim alluded to earlier on, any solder paste of any size or any manufacturer, do your solder paste evaluation. There are some companies out there who do it right and there are others that leave a lot to be desired so you have to do a thorough solder paste evaluation. Jim But there are certainly multiple suppliers who are making very good type four paste today that will solder under a wide, wide variety of conditions and print under a wide variety of conditions. Phil Well I think we answered that question. You have been listening to Board Talk with Phil and Jim. And whatever you do, whatever paste you're reflowing, don't solder like my brother. Jim And don't solder like my brother. |
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