Issue link: https://iconnect007.uberflip.com/i/1481368
50 DESIGN007 MAGAZINE I OCTOBER 2022 ferences between mSAP and A-SAP, and what it means to designers and design engineers? A: SAP stands for semi- additive processes, and there are a few versions out there such as mSAP and A-SAP. We call them semi-additive because they all start with a thin layer of copper before creating the circuitry. is can be either from a copper-clad mate- rial, similar to what we use in traditional PCB manufacturing but with thinner copper, or a non-clad material where the PCB factory plates the seed layer. e dif- ference between mSAP and A-SAP is the thick- ness of the seed layer where mSAP starts with a copper layer, typically 3–4 microns, while A-SAP starts from an unclad material activat- ing the surface, adding a very thin chemical copper layer of less than 1 micron. en both processes use photolithographic methods to plate up copper traces to around 20-micron thickness before flash etching the seed layer. Basically, the thickness of the seed layer, as we see with A-SAP, is the main factor for the pro- cess to create thinner traces. Q: How is designing in the ultra HDI arena dif- ferent from designing a typical PCB? What are some of the hurdles? A: Designing ultra HDI is a challenge today because of a lack of standards, both for PCB production and material availability. e big hurdle today is fabrication availability. ere are processes and some materials available, but very few PCB factories can offer anything below 40-micron trace and space. Some facto- ries claim to offer UHDI, but that is very oen only down to 35- to 40-micron traces, while the components you want to use requires traces and spaces below 30 microns. Q: Are there any resources— books, websites, instruc- tors, etc.—for UHDI design techniques? A: For designers who want to learn more about UHDI, there are a limited number of resources. I would start with Tara Dunn's Altium blogs and her I-Connect007 columns, which oen cover semi-additive and UHDI. Anyone consider- ing moving into ultra HDI should follow the NCAB blogs, available on our website and on LinkedIn. Read everything that you can. Q: What advice would you give designers who are considering moving into UHDI? A: e best advice I can offer is to find a sup- plier and be sure that you design within their capabilities. NCAB has a plan to be providing high-mix, low-volume UHDI starting as early as 2023. Today all factories that offer less than 35-micron traces have extremely long lead times. Not to sound commercial, but NCAB Group has a clear plan to change that. We are not there yet but will be very soon. I am leading the NCAB Technical Council, and one of the focus teams is working actively with ultra HDI. As soon as we have a factory that can offer shorter lead times on UHDI, we will develop design guidelines and webinars, and provide workable parameters for design- ers. We need safe parameters to secure manu- facturing yields and product quality from the start. It is paramount for NCAB Group to be transparent about what we can offer and how ready we are with new technologies. DESIGN007 Jan Pedersen