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42 SMT007 MAGAZINE I AUGUST 2019 and qualified. Solder mask, for example, now becomes a truly additive process. There are several solder mask properties to investigate, including digital solder mask technology, pro- cess step removal, environmental extremes, heat management, crack reduction, and via filling, just to name a few. In this article, I will begin to explore the "hows" and the "whys" involved in making solder mask a strictly addi- tive process. Going Digital One of the most important ones was the property function of imaging the material. PCBs have much tighter space requirements as devices get smaller and more processing is required that pushes PCB manufacturers to implement some form of digital printing into their process. Taiyo has spent several years in developing not only laser direct imaging (LDI) solder mask for the very popular Orbotech Paragon machine, but we have also designed direct imaging (DI) solder mask for various other DI equipment options that are now avail - able. These LDI/DI solder masks offer excellent advantages over traditional liquid photo-image- able (LPI) solder mask processes with regards to registration, tight tolerances, and fine dams. However, the true leap in digital solder mask technology is inkjet solder mask. For the past several years, Taiyo has worked with inkjet equipment manufacturers such as Orbotech and Notion Systems, just to name a couple, pushing this technology into the marketplace. Inkjet solder mask allows you to enjoy the many advantages of LDI/DI, such as registra- tion, no artwork generation or the waste/cost associated with it, and the capability to do fine features. You also gain the benefit of not leaving solder mask in the hole or on the pad because inkjet solder mask will never leave residue on pads or in the plated through-holes. This new solder mask application method truly becomes an additive process. Process Optimization In becoming an additive process, solder mask can now remove multiple steps in the current process. No more waste development solution that must be deposed of and no more artwork generations waste disposition. Tack drying and the associated solvent that is dissi- pated into the environment is gone. Thus, ink- jet solder mask not only saves you money in processing cost, but you are making the envi- ronment greener. When would you have ever thought you would have heard that statement before—a PCB process that is environmentally friendly? Although the cost savings will vary from PCB manufacturer to manufacturer due to labor cost, markets served, board technol- ogy, etc., it is obvious there is money to be saved and opportunities to be taken. New Performance Requirements As if 5G wasn't a harsh enough new require- ment for engineers to deal with, the automotive industry is certain to keep the printed circuit manufacturing industry awake at night thanks to the continual new thermal cycling require- ments. With each new vehicle model, the PCB footprint inside the vehicle increases. The elec- tronic functionality of a vehicle increases as features—such as lane control, massage seats, cameras, and energy-recycling alternators to charge your batteries—become more and more common. Figure 2 suggests the rate at which these features will continue to grow. Heat Management Many of the PCBs required to introduce these new features are built with higher layer PCBs have much tighter space requirements as devices get smaller and more processing is required that pushes PCB manufacturers to implement some form of digital printing into their process.