Photoresist (photo from the English: resist) – polymer light-sensitive material that changes the physical and chemical properties when irradiated with light. Is applied on the cultivated area in the process of photolithography or photoengraving to obtain corresponding to photomasks placement of windows for access to corrosive or other substances to the surface of the material being processed.
Exposure is performed in the ultraviolet range (photolithography) by electron beam (e-beam lithography) or soft X-ray radiation (X-ray lithography). The impact breaks the polymer (a positive photoresist), or, conversely, causes its polymerization and lowers its solubility in a specific solvent (negative photoresist). In subsequent processing occurs corrosion in “windows” formed by the illumination (positive photoresist) or neosvetyavaneto (negative photoresist) on certain sections of the polymer.
The resolution of fotorezista is defined as the maximum amount of minimum size elements per unit length (1 mm). R = L / 2l, where L – length of the section, mm; l – width of the element, mm. The resolution of the positive photoresist is considered to be higher, which determines its wider use.
There are two main types of photoresist used in the manufacture of printed circuit boards: Dry band photoresist (SPF) and aerosol «POSITIV». SMA has received more widespread in the industry, because provides a uniform layer. Represents three-layer “sandwich” – two layers of protective tape between them – a layer photoresist. To the treated surface is bonded through the laminator. One of the largest manufacturers of SPF is the company DuPont (USA) selling it under the trade name Riston, in coils by 152 meters.

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