Blue LED products come out, open the full color of the LED billboard display panel application development, due to the emission characteristics of light-emitting diode, LED with a small size, low power consumption, long life, resistant to collisions, etc., with the production technology and equipment improvements, rationalization of product prices accelerated, and then expand the LED industry in applications such as home appliances lights, car lights, traffic signs and outdoor billboards and other large-scale. Successful development of white LED, it will be the interior lighting and mobile phone replacement backlight panel, LED industry, the wider the field of the future market.
Photoresist is used in many industrial processes, the photosensitive material. Such as lithography, can be engraved in the surface coating layer of a pattern.
There are two photoresist, positive photoresist and negative photoresist.
Positive photoresist is a photoresist, the portion soluble in light shine photoresist developer, and not shine some light not soluble in photoresist developer.
Negative photoresist is a photoresist, the shine will not dissolve in the light part of the photoresist developer, but not part of the light will shine soluble photoresist developer.
The positive photoresist agent is mainly negative type photoresist used in the LED chip manufacturing metal electrodes evaporated Lift-off process, since the LED electrode metal used in ways not easily produced by etching circuit patterns, so the use of their roots (Lift-off) lithography, are protruding (Overhang) photoresist graphics, so that the metal in the evaporation process will not be covered in the photoresist on the continuity, then the way to the photoresist is not being metal cloth cover, some photoresist roots of metal electrode pattern.
Is commonly used in semiconductor process-type photoresist, optical exposure mode, the upper photoresist resist receiving high energy than the lower, making the positive type photoresist imaging most of the graphics for the narrow width, not after the first exposure mode Overhang of the graphics that are in the negative-type photoresist imaging coincided with the positive type photoresist image contrast, so the negative type photoresist lift-off process is the best choice.
For example ENPI200 photoresist is mainly based on phenolic resin (Novolak) and light acid as the main chemical increase convergence (Chemically amplified) negative type photoresist, the phenolic resin can be dissolved in alkaline aqueous solution, compared to the quality of rubber (Rubber type ) negative-type photoresist with environmental advantages. The photoresist imaging principle is, in the light acid exposure received by the energy block the production of acid, and then by baking at high temperature after exposure to phenolic resin produced with cross-linking agent Cross-linking cross-linking reaction of the left pattern. High resolution lift-off photoresist EPI622, you need to meet customer specific processes can be reduced to Overhang Width 1um resist the following chart, which applies to high-brightness LED thin wide process.