Topics of the Week
INTERNEPCON 2007 (Continued)
This is part two of my observations from the 36th InterNepcon held at Tokyo Big Sight from January 17th through January 19th. There were not many multi layer board manufacturers and flexible circuit manufacturers represented at the exhibition. We could see an industry trend towards finer traces, smaller via holes and finally higher circuit densities. 100 microns diameter via holes (4 mils) by mechanical drilling was very common for the board manufacturers. Many companies at the exhibition said they were able to generate smaller via holes than 40 microns diameter (1.6 mils) using UV YAG laser, thus making a 30 micron pitch trace (1.2 mils) not so special for both rigid boards and flexible circuits. Several flexible circuit manufacturers had on display ultra high-density circuits. Nitto Denko, one of the major flexible circuit manufacturers in Japan showed 20 microns pitch traces (0.8 mils) built by a roll-to-roll manufacturing process. An engineer explained that it was made by semi-additive process, and it is ready for volume production. Taiyo Industrial, a prototype shop for flexible circuits displayed several flexible samples with 15 to 17 microns pitch traces. They were less than 0.7 mils pitch. Taiyo said that it accept small volume production for the ultra-high density circuits.
One category that was a hit at the show was ultra-fine screen printing. There were few equipment manufacturers and many screen suppliers. They were pitching the low cost capabilities as the alternative solution to the traditional lithography or direct imaging process. Machine manufacturers for the screen printing segment presented fine capabilities smaller than 20 micron pitches. MicroTech, an equipment manufacturer said it could provide roll-to-roll machines for the 20 microns pitch lines. Most of the screen mask suppliers displayed the high-resolution capabilities; the 30 microns pitch was the minimum. Naganuma Art Screen demonstrated 15 micron pitch resolution (3 micron lines and 11 micron spaces).
An issue that arises from screen-printing is ink material. The manufacturers said that it was relatively easy to have fine conductive ink material to generate 10 microns line and space for the green sheet of the multi-layer ceramic circuits. There have been some resist materials as the etching resists, but manufacturers did not talk about the etching solutions and conditions. Another challenge is to get conductive paste for the fine line printing. A couple of material suppliers said their nano pastes could be the solution; however, no nano paste could satisfy all of the basic requirements such as conductivity, resolution and bond strength on the substrates. Another big hurdle for the nano paste to overcome is cost related. Customers are expecting a remarkable cut in costs by screen printing processes; therefore, the circuit manufacturers and end customers are looking for a suitable conductive ink material.
Dominique Numakura, DKN Research (email@example.com)