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16 The PCB Magazine • June 2016 that amount. When using dry film photoresist. The DF will now extend beyond the wall of the drilled hole. 1. Two things will happen with this ar- rangement: 1) the plating bath will be forced to throw into the hole, improving the distribu- tion; 2) There will be no land except where the trace enters the hole. 2. After stripping and etching, there will be landless vias with the trace dropping into the barrel of the PTH or blind via. 3. This process does not work for panel plating. Then you have to use the next process like NEC. Positive Liquid Electrophoretic Photoresist When I first saw this process in Japan in 1985, they were using a positive-acting electro- phoretic photoresist from Nippon Paint that evolved from the electrophoretic paints used on automobiles. A similar photoresist was avail- able in the USA and Europe from Shipley. A more recent photoresist and process came from PPG Industries and is documented in a paper by Patricia Goldman (formerly of PPG) and Tim Schmidt of Compunetics [4] . The positive- acting photoresists have many properties that can be very useful. The most useful is multiple AGAINST THE DENSITY WALL: LANDLESS VIAS MIGHT BE THE ANSWER Figure 5: More landless vias including three more examples of invisible vias. a) Laser drilled 0.1 mm blind via in a 0.1 mm trace; b) two landless vias on a 0.008 in (0.2 mm) TH; c) The one view shows 0.2 mm pitch traces with 0.1 mm landless vias and the proportional size if there were 0.2 mm, 0.4 mm or 0.35 mm lands on the vias; d) 0.1 mm trace in a plasma-etched, 0.2 mm blind via.