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PCB-July2015

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72 The PCB Magazine • July 2015 For pattern plating, one would have to choose a resist that is at least as thick as the intended plating thickness, which is a design parameter and cannot be changed. A typical plating film thickness is 50 micron. In fact, the plating resist should be a little thicker than the intended plating height so that there is no over- plating in areas of high current density. Figure 3 shows a severe case of over plating. Over-plating (i.e., plating over the resist [mushroom plating]) and trapping the resist un- der the over-plated copper (and tin) will cause stripping problems. If the trapped resist can- not be stripped, it will act as an etch resist and will cause a short due to remaining base cop- per between plated lines. If the resist is partially stripped, leaving random resist residues on the plated side wall, inhibiting the natural etch- back so that the plated copper will look ragged (Figure 4). PCB DRy FILM PHOTORESIST THICKNESS SELECTION CRITERIA continues karl's teCh talk Karl Dietz is president of Karl Dietz consulting llc. he offers consulting services and tutorials in the field of circuit board and substrate fabrication technol- ogy. To view past columns or to reach Dietz, click here. Dietz may also be reached by phone at (001) 919-870-6230. Figure 3: over plating. Figure 4: incomplete resist stripping causing ragged plated lines. Brian haken, one of the PcB industry's great lead- ers and visionaries, has passed away. an inspiration to many in the PcB field, haken helped form the close ties and friendships that have bonded the uK's PcB industry together for many years. haken worked for e.K. cole TV, before moving to multitone electronics, and to south east Printed circuits as sales direc- tor. in 1987, he was instrumental in form- ing the Printed circuit industry Federation (PciF), which he led as director from its in- ception until the merger with the Fei, and later intellect, in 2000. The PciF was the lead federation representing uK printed circuit manufacturers, suppliers and assembly companies. its success was a testament to haken's en- ergy and drive. The regular quarterly meetings were eagerly attended and the annual conferences at run- nymede were always exceptional. haken helped steer the uK PcB industry to wider markets, forging close ties with the iPc in the united states and JPca in Japan. it is particularly sad to note that his wife eileen also passed away a week before. haken's funeral was held June 23 at southend crematorium in west chapel. To make a donation to cancer research in his memory, click here. UK PCB Industry Leader Brian Haken Passes Away

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