Electrodepositable resists polymers

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Hydrophobic solvents (or plasticizers) are often added to electrodepositable resists to lower the Tg of the polymer, enabling electrodeposition to take place at low temperatures and allowing easier control of the film thickness. The coated resist can also flow better (coalesce) during baking, when a plasticizer is present, to give a more compact, defect-free surface. 

Hundreds of baths exist for electrodeposition of gold and its alloys . The latter are more wear resistant, so better for contacts . Polymers incorporated in cyanide-bath deposits affect wear and contact resistance . 

Industry, however, favours electrodeposited palladium-nickel alloy since it is cheaper than palladium, harder and less prone to cracking, fingerprinting and formation of polymer films Its wear resistance is poor, so it is usually given a thin topcoat of hard (sometimes, soft) gold. ... 

It is also possible to electrodeposit multilayers in cylindrical pores of a suitable etched polymer membrane. Typically, wires with diameters of about 100 nm and length of 5-10 fim can be obtained. The deposition cycles are similar to the ones described above. Magnetoresistance [this is a term describing the relative decrease (increase) in electrical resistance of a material when subjected to a magnetic field longitudinally (transversely) to the current flow] measurements with the current perpendicular to the planes are possible. In addition, giant magnetoresistance (GMR defined below) effects may be observed as well. 

By the process described above, a plasma film could be obtained that had high enough electrical conductivity to allow direct electrodeposition of copper. The bulk resistivity of film measured by a four-point probe was 2.6 x 10 " ohm-cm for the copper-containing polymer film when deposition was stopped after 18 min at HOW. This value is critical if a uniform electrolytic deposit is to be obtained. For safety, deposition was carried out until a total film thickness of 150nm was obtained, giving a nearly pure metallic layer thick enough to allow subsequent electroplating. 

The polymers are generally deposited on inert substrates such as platinum, gold or glassy carbon electrodes and on indium-tin-oxide (ITO) transparent electrodes for electron spectroscopy. In the latter case differences were observed in the optical spectra of poly(3-methylthiophene) films electrodeposited on electrodes of different surface resistivities [46]. However, electrodepositions have been also performed on other surfaces such as titanium [49] or iron [50]. 

Following this introduction, the chapter continues with a description of the principles of electrodeposition (section 2.2). The various types of polymers employed in ED resist formulations are then described (section... 

Polymers for ED resists have been covered extensively in section 2.3. The polymer contains ionizable groups for both electrodeposition... 

The process of electrodeposition has been developed to provide uniform, highly adhesive, corrosion-resistant primer coats, particularly for the automotive industry. (The ultimate solution to the corrosion problem is simply to replace metal with plastic, as is done for many applications.) In the most common form of the process, polymers that contain carboxylic acid functionalities are produced. These polymers are then solubilized in an aqueous medium by partial neutralization with a base to give macroanions (P represents a polymer backbone) the macroanions are beheved to exist as micelles. 

---