The Complex World of Soldering


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Our biggest struggle is making sure that if you call a component out, your footprint should actually meet what the manufacturer of the component recommended. We do run into quite a few times here where the customer will call out a part, and it doesn't quite fit, which means that you don't get proper solder joints, you don't get the heel fillet that you want, or the side joints that you want. Then they don't meet IPC standards. It's a struggle to keep going back and forth between the customer and the manufacturer trying to make sure the component still functions. So verifying that you're setting your board up for success with proper pad size would be a good thing for customers to know.

Las Marias: What else do you think should the readers know more about when it comes to soldering?

Holden: Some of the effects that different formulations of lead-free solder paste has when it's reflowed, in terms of interacting with final finish and interacting with land size, is that they don’t spread like tin lead, and we find smaller pad sized footprints because it’s a stronger joint than tin lead. We’ve always watched very closely the Japanese and the JPCA standards, because they’ve been using lead free for 10 years longer than North America. Since a third of all of our output goes to Japanese automakers, we’ve got a lot of cooperation with Nissan, Honda, and Toyota about what they recommend.

Las Marias: Standardization is still an issue?

Holden: It's all a point of view. Like I said, we're such as big industry that I’ve been talking about automotive electronics, which were going for a 15-year useful life—and that’s a lot different than a mobile phone. We virtually test 100% of every lot because the Japanese or the German auto companies insist on that. If we ever have a failure, we have to go back into root cause analysis. A lot of my experience deals with reliability because warranty failures and things like that is a big bug-a-boo in automotive. But depending on which industry you’re in, there's a lot of differences. Most mobile phones don't make it past two years before they've been dropped in the toilet, run over, or just that everybody turns them in for the new models.

You have to support your customers, and not all customers have the same needs. It’s the final performance that our customers required. They weren’t dictating a design or a process, only the final performance, whereas if you're an EMS and you have multiple customers, you have to keep shifting it all the time depending on what the requirements are. We still have wave solder machines. They're lead free, but they’re still wave solder.

Cox: We do too. We do a lot of military and oil and gas that we build predominantly through-hole. We have a lead one and a lead free.

Holden: Lead free is a lot tougher than the tin lead.

Cox: Yes. I was thinking about it and a lot of what I've experienced here in the last couple of years is our customers will sometimes call out to use a lead-free no clean solder on their boards. Then they are upset with us that their boards do not look clean and the solder looks to be disturbed. Really, the industry needs to know having a lead-free solder is going to look more grimy than using leaded solder. They look different. A no-clean solder doesn't necessarily mean that it's going to be clean. You're going to have residue there, but it's not active flux residue. The different types of solder that you run into along the way, whoever you use should talk to you about the way your solder is going to look before you actually put it on the boards. I think that’s a big thing. Our customers come back and say the boards are dirty, but they’re not. They meet IPC standards and they use a no-clean flux, which will leave slight residue on their boards.

Holden: That's one thing I can't ever remember reading or seeing: a breakdown of the soldering industry by what all of the different types of solders look like, in terms of a picture, whether clean or no clean. Then, their interaction with final finishes, and then what industries they are preferred by in terms of a matrix. A lot of people tend to get confused, because if you're talking about the communications industry, that may not apply to the consumer industry; or when we're talking about automotive, that might not apply to medical. You haven't always seen these things. Nobody’s ever come out and given us matrix of what they’re supposed to look like, and maybe what the estimated life is in terms of their interaction with land patterns, with final finishes, and with percent of voiding. That chart or definitive explanation has not been out there.

Cox: I agree. A lot of customers I know say, ‘Oh, if I have the choice between the no clean or the aqueous, I want to go with the no clean because that means my board will be clean.’ But in reality, it means that you don't need to clean the board because the residue that's left isn't active. You will actually have a cleaner board, appearance-wise, if you use an aqueous flux. Then you can wash it and there is nothing left behind. That’s something we struggle with over here a lot with our customers. It's just a miscommunication of what they're actually using, what the product is doing, and how it's going to look.

Las Marias: Cathy and Happy thank you so much again for your time and your insights.

Cox: Thank you.

Holden: Sure.

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