#1816 / Metallization For Plastic Surfaces

 During the 1980’s, high density flexible circuit manufacturers ran around the barn a few times trying to decide the best way to produce a reliable bond strength between polyimide sheets and copper foils when producing thin copper laminates for high density flexible circuits. The two processes used to metallize surface of polyimide films are a sputtering process and electroless plating. Sputtering generated a reliable adhesion for thin metallic layers on the inert plastic films, but the process was not productive because manufacturing had to be conducted in vacuumed chambers. This significantly increased the price for metallized films. A Chemical plating process was simple and productive and had a lower manufacturing cost. Manufacturers preferred the lower priced chemical process; unfortunately the chemical process was not stable, nor did it produce reliable bond strength for thin copper laminates. Most manufacturers chose the sputtering process in spite of its high cost for the fine line circuits of the COF (Chip on Film) substrates. Eventually, it became the industry standard.
 Business opportunities using the electroless process dwindled during the 1990s and 2000’s; however chemical companies did not completely give up. They improved the process remarkably by introducing a new surface treatment process over the last few years, and more chemical suppliers threw their hat in the ring. Suppliers do not disclose detailed information about these chemicals, but there are sets in the chemical processes. DKN research conducted a series of evaluations for these chemicals, and these new chemicals provides a more reliable bond strength for metallized layers on polyimide films compared to chemicals used twenty five years ago. The cost for the new processes increases, but they have elevated performances because of their higher productivities. Additionally, the new chemical process provides additional advantages compared to other physical metallization processes including sputtering.
 The first advantage is the processes can double side metallization using the same process as single side laminates. This is a huge advantage for new COF substrates due to market trends. The next generation driver modules for flat panel displays will require finer traces down to 20micron lines and space with smaller micro via holes less than 20micron diameters. The plating process using the new chemicals can produce a wide range of double sided copper laminates down to 0.2micron thick metallization.
 The second advantage using this process is the wide variety of substrates available. Traditional polyimide films are available using this process. New polyimide films including transparent versions are also available. Trials using other plastic films (PET, PEN, LCP, PEEK ) and several types of fluoride polymers were successful in producing unique copper laminates. There are a few of them that can effectively make larger sized piezoelectric devices such as mechanical sensors and actuators.
Several flex circuit manufacturers developed a new semi-additive process using new chemicals to generate ultra fine traces down to one micron line and space for not only single sided but also double sided and multi-layer circuits.
 The new plating process will create more functions for printed circuit manufacturers. DKN Research is happy to share technical information; feel free to contact us via email or phone.

(978) 372-2345

Dominique K. Numakura, dnumakura@dknresearch.com
DKN Research, www.dknresearch.com

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(Please contact haverhill@dknreseach.com for further information and news.)

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