Polymers for electrodepositable resists

A variety of electrodepositable film forming resins are known, the most often utilized to date being acrylates, epoxies and novolacs, although the 

Structural examples of the three most commonly used resins are shown in Fig. 2.4. 

The synthesis of these polymers is carried out using standard methods, and is described in detail elsewhere [6]. In order for a polymer to be electrodepositable, it must contain a distribution of ionizable groups along its molecular chain. Polymers may be cationic, containing basic sites such as amino groups, or they may be anionic, containing acidic sites such as carboxylic, sulphonic or phosphoric acid groups. 

In some instances amphoteric polymers are known with both acidic and basic groups in the same chain. 

In the case of resins for photoresists the polymer may also contain photosensitive functionalities, such as sites of unsaturation in the case of negative-working photoresists, or have photo-active groups such as diazonaphthoquinone (DNQ) attached, as in positive-working photoresists. Although some polymers are formulated with such functionalities present, in the most commonly used polymers such groups are absent and the main function of the polymer is as a carrier for the other resist additives (section 2.4.1). 

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