Issue link: https://iconnect007.uberflip.com/i/1527613
38 DESIGN007 MAGAZINE I OCTOBER 2024 Partial HDI has shown itself to be very use- ful, allowing designers to escape route tight- pitch BGAs without moving to full HDI and the required sequential lamination. It's almost the best of both worlds. Chris Hunrath, vice president of technology at Insulectro, believes that mSAP just might be the trick for designers considering partial HDI. As Chris explains, the materials and equipment required for the mSAP process are easily avail- able, and the process is well established. is could be a great option for designers working with BGAs that have a pitch of 0.5 mm or less. Andy Shaughnessy: Chris, why would some- body choose to move to partial HDI? When does that process make sense, and when is mSAP the answer? Chris Hunrath: It's all about BGA pitch, micro- via location, and circuit routing. I've not heard anyone call it partial HDI, but I like that expression because that explains it just right: the rest of that layer or the board might be more, let's say, conventional. But you neck down the traces to be able to do your fan-out. One of the things I've learned in the past cou- ple of years from designers is that it's okay to make the trace narrower—you won't degrade the signal integrity as long as that neck-down area is a short length. You can get your routing and still have some registration budget where you won't risk having defects like shorts and whatnot. First, there's a lot of what we call "head trash" about exactly what mSAP is. It's also really One Partial HDI Technique: mSAP Feature Interview by the I-Connect007 Editorial Team