Issue link: https://iconnect007.uberflip.com/i/1481368
OCTOBER 2022 I DESIGN007 MAGAZINE 13 who want to get involved? What will they need to learn and upgrade? Snogren: On the equipment side, you must invest in direct imaging equipment that has 20-, 25-micron feature size capabilities or less. You find resists that are compatible with your imaging system. en there's AOI equipment. You need specialized plating equipment for doing simultaneous pattern plate and micro- via filling, and equipment for handling thin foil and ultra-thin foil, 1- to 3-micron foils, and differential etching equipment. If they want to go fully into semi-additive processing, they should look into something like Averatek or eSurface to get electroless copper to stick to a wide variety of laminates. Shaughnessy: Because this is all build-up at this point, right? You can't do subtractive at this level. Snogren: It's difficult. Asian fabricators were doing subtractive down to 30- to 40-micron lines and spaces. Once they hit that point, most of them started using modified semi-additive processes. One big aspect is cleanliness. I don't know that any of us in the U.S. understand the cleanliness aspect of it, and how clean our pro- cesses must be. Once you start running in vol- ume, those small particulates that don't bother you when you're at 3-mil line and space sud- denly become a big percentage of a 20-micron line and space. We may have to deal with much different environmental issues in our factories with clean air, water, and processing tanks, ultra-filtration, special handling. It's going to be different. Nolan Johnson: It seems that we're down to the dimensions that triggered cleanroom environ- ments in the IC world 20 or 30 years ago, and that was very successful. We will be looking at that for our fabrication facilities in those dimensions as well, which will raise the cost of a UHDI facility. Snogren: Yes, it will be difficult to justify having this cleanroom environment and ultra-filtered processes and air just to build standard 4-layer or 6-layer 4-mil line and space products. at's why some Asian factories doing these types of products are specialized. All they do is build these HDI and ultra HDI products. Shaughnessy: It seems like a big opportunity here for our fabricators. Snogren: It's a chicken or the egg scenario. You must develop the capability and hope people will buy it. But if you don't develop the capa- bility, they won't even design those features because they can't get it. It's a tough invest- ment decision to make for companies in North America. But I believe if you have the capability and demonstrate it, people will begin to design products that take advantage of that capability. Shaughnessy: Will UHDI change the PCB designer's job? Snogren: e HDI design standards in IPC-2226 don't really address some of the requirements for feature sizes, alignments, and spaces below 50 microns very well. at's something that our D-33-AP committee is trying to address. How do the design standards need to change or how do we need to adapt them for ultra HDI features? Here are some things that we've already iden- tified: e plating thickness requirements, annular rings, and dielectric thicknesses are different. We may not even use foil if we go to semi-additive, and many of the design standards It's a chicken or the egg scenario. You must develop the capability and hope people will buy it.