Issue link: https://iconnect007.uberflip.com/i/869081
16 SMT Magazine • September 2017 the paste is not the right thickness. It could be the profile on the original assembly that's caus- ing the issue. To fix the problem, it's back to the customers to figure out what step in their pro- cess is causing an issue," she says. "They're more likely to have the data or the tribal knowledge and the cause of the problem and we might just be able to have the equiva- lent expertise to solve the problem," says Pat- ten. "We don't always get involved in a recom- mendation. Sometimes, we do and we certain- ly can, but to learn that entire process for that build and the profiles and so forth doesn't al- ways go through our hands." "We have some customers that work with us while they're doing their proto stage of as- sembly," says Ripoli. "They'll come back to us and send us a board with connectors and have us measure the solder fill percentage, the X-ray. We'll give them that feedback, they'll go back and make changes to their process, send us an- other batch of boards, and we go through that same process again until they can tweak and find the right solutions to getting that proper fill." One of the biggest issues when it comes to rework and repair is the temperature cycles. "The problem is when you have to rework something, it has to go through four or six cycles of heat or something like that. Then it's a problem and they didn't predict that. Nobody predicts reworks on their boards," says Price. "Not only that, but you won't necessarily know that the board has been repaired multiple times be- fore it gets to you," says Patten. Most of the time, the rework specialists will never find out how many times a customer— the contract manufacturer/PCB assembler— touched the product before they get it. "It is a big mystery," says Patten, "and it's often a cause of unpredictable failures." But some PCB assemblers/contract manu- facturers do track the number of rework/repair cycle that a board goes through. "When we get larger quantities of rework or repair, we don't see that as often; but when we have the one really special custom board, we get that a lot. They tried and they failed, so they give it to us. We don't know what they've tried or how they failed. We don't get that history usually," says Patten. Key Considerations When someone's looking at their rework strategy, what are the important considerations that they should be mindful of? According to Price, it starts with the skill of the operator. "The folks that you have doing the work must have a tremendous amount of experience, hand skills, the ability to work using magnifi- cation for hours on end, knowledge, patience; everything ties in with the operator doing the job. When it comes to rework and repair, ev- ery board can be a little bit different. When re- working and repairing circuit boards, the op- erator must be reading the board all the way through the process. That's why the procedures that you look for repair are fairly generic in na- ture because you just can't create a procedure that identifies every subtlety that you're going to confront along the way. In my opinion, it starts with the op- erator and the need to have a well-trained, highly skilled op- erator doing the work. Second- ly, having good modern equip- ment and tools that allow your skilled operator to succeed. [For example] A soldering sta- tion that can drive heat into a board very quickly. Having the proper tools and equipment is a major requirement," Price explains. "I'll tag onto that," says Pat- ten. "Just as much as I want to sell more training, and I believe in high training, a certification is not enough. It's the experience of the hundreds of situations. You can't have a week of a training class. Sharp mind, sharp tools, and a ton of experience. Finding those people, they're diamonds, they're very hard to find." He adds that you can train thousands of people, but only one or two of them are really going to be a long-term high-end tech. A LOOK INTO PCBA REWORK AND REPAIR Gary Freedman