Issue link: https://iconnect007.uberflip.com/i/1513827
JANUARY 2024 I SMT007 MAGAZINE 33 Ripoli: You also need an operator, a QC tech who's certified to inspect to the IPC specifica- tions. Patten: All the customers require an inspec- tion to the IPC-610 standard, as well as some- one who knows how to read and interpret the X-ray because that's not specified in the 610 standard. Nash Bell: When our customers come to us with a problem, such as a BGA removal, we have multiple ways to remove that BGA that may reduce the risk to adjacent components or the rest of the board. We have the knowledge, expertise, and a lot of very skilled people with experi- ence doing that type of work to tell us what the best method is to remove that BGA and minimize the risk of compro- mising anything else on that board, too. at tribal knowl- edge is important as well. Patten: We could have a whole separate conver sation just to tell designers not to put 5,000 0201 components next to a BGA. We'd tell them to put a little space in there because if that BGA ever has to come off, there are only two ways, and they require a lot of heat. If the small components were fur- ther away, designing for repairability could go a long way, but no one is doing that. ink of the phone in your pocket, for example. ere are multiple BGAs on that phone. It's not Class 3, and it's not repairable. Unless there's just a cracked screen, it gets thrown away. You mentioned multiple ways to remove a BGA? Patten: We certainly have ways using the tradi- tional method of heat, because that's how you melt solder. We find underfilled components to be the most challenging with heat because the underfill beneath a BGA melts at a differ- ent temperature than the solder. It's pushing It's fun being able to do projects we couldn't do previously... solder balls and squirting everywhere. Some- times heat is not the solution, in which case there could be no solution. We have recently acquired an ESD-safe mill- ing system that can mill down in layers—down to one-micron layers at a time—to do cold removal of chips. is allows removal of BGAs so we don't have to put the board through mul- tiple heat cycles to get the component off. ere are only so many times you can apply heat cycles to a single board, and you definitely hit your limit somewhere around eight times. Now we're cold-milling chips that have no value, but the board still does. What's beauti- ful with the underfill is it's like leaving a stencil in place with a little bit of solder. If I get that down to about six-thousandths of an inch, it's no different than a 6-mil stencil. I could put a new part right on top of it. It's fun being able to do proj- ects we couldn't do previously because the y ields weren't in the high 90% range. Even BGAs that aren't underfilled sometimes work fine—and sometimes everything just goes wrong. We have not traditionally warrantied work on any- thing underfilled, but customers still take that chance, so we found a better way for them. You mentioned cold milling, which is new to me. Are there some other new techniques that might not be so well known? Patten: It's easily the newest technique in the last 10 years. We switched from hot air sta- tions to infrared rays, which has helped with certain situations. We're unaware of anyone else with a commercially available cold milling solution and vacuuming for ESD and foreign- object debris (FOD). I know some big players are experimenting with this, but it's usually the prototype houses or Department of Defense projects because they're only making 100 of something, like $100 million antenna towers.