Issue link: https://iconnect007.uberflip.com/i/1038326
OCTOBER 2018 I PCB007 MAGAZINE 47 drives that allow the sys- tem to vary the pressure. For microvias, we want to run at high pressure and high frequency. After all, you have to get it down to the bottom of that via. Holden: We're seeing that there are elements of the recipe and nuances for op- timization that haven't been done in the past. Foley: If you think about it, the U.S. method is all ver- tical. It's all "dippy dunk." The advantage of the hor- izontal system with fre- quency drives on the mo- tors is that you get that so- lution down to the bottom of the via. In a ver- tical line, you're dependent on the stroke of the agitation. Holden: Let's talk about the chemical dosing portion of the system. Foley: The back wall has chemical dosing for several different lines. Some of them have fair- ly large pumps. You could have one pump for dosing and a second for makeup. If we use the same pump for dosing and makeup, some of the makeups would take several hours. Thus, we install a slightly bigger pump for makeups. Goldman: What is the throughput on this line and does it vary? Foley: Usually, the low-build electroless copper line is designed to run at one meter per min- ute. This can be combined with the plater for strike plating at the same speed. However, if full-panel plating is required, then the speed of the plater is reduced and the electroless copper panels are fed into the plater. At the beginning of the Printoganth TP1 bath, we have a unique roller patented by Atotech. There is a stainless steel roller, an anode, and a cathode. When the panel comes in, it gets a small electrical charge, which kicks off plating as soon as panels enter the bath—even at the first roller. Otherwise, plating starts much later (several feet further down the line). It helps with the thickness if you kick it off right at the begin - ning; that's another unique thing to Atotech. On the other line, you'll notice that the roll- ers are much larger in diameter than the rollers on this line, which are slim rollers. This goes into our pre-dip and palladium activation. Goldman: What's the target deposit? Foley: Anywhere from 0.76 to 1.2 microns, de- pending on what is running. Compared to all the other electroless baths I've worked with over the years, this is a much more stable bath. We've been in production now for close to six months with the same electroless bath. I've yet to see a bath plate out at GreenSource, which is a typical problem in the industry. When the line shuts down at the end of the day, several spray bars will spray off the con- veyor for 30 seconds. The conveyor will run for another 10 minutes cleaning up and re- turning everything back to the bath. It might dilute the bath a bit, but it keeps the work- Figure 10: Frequency-controlled high-efficiency motors pumping all process modules and rinses.