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Electrodeposition Photoresist --- A New Technology of HDI PCB Manufacturing

by: Oct 17,2019 1040 Views 0 Comments Posted in PCB Manufacturing Information

Electrodeposition Photoresist HDI PCB

Introduction:

With the rapid development of PCB, there are many challenges and much higher requirements of PCB, such as high density, high speed, miniaturization and so on, which makes the traditional manufacturing technology not meet the requirements of these new PCBs.

The Traditional Patterns Manufacturing Technology of Multilayer PCB (Take out-layer patterns as an example):

After making the inner patterns of multi-layer PCB (MLB), and then it will carry on laminating, drilling and PTH. And after these processes, it will enter the stage of making the outer patterns. The traditional manufacturing technologies have the following two kinds.

1)      Pattern Plating and Etching

After PTH, both the hole and the surface of PCB are copper layers. First, the surface of MLB is coated with the photoresist, and it is exposed in a specific wavelength range in order to polymerize the photoresist that is not covered by the patterns. Second, removing the negative and then going on development, so that the surface of the MLB produced the required patterns. Next, electrical plating is carried out to thicken the copper layer, so as to ensure that the thickness of copper layer on the wall of holes reaches more than 25um. Finally, a layer of Pb/Sn alloy was electroplated on the copper layer to protect the copper layer, and then etching, so as to obtain the surface conductive pattern.

2)      Tenting and Etching

After the MLB surface is coated with a layer of photoresist, it is exposed and developed in the same way, but the negative patterns are obtained, that is, the lines and holes are covered by the photoresist, and the copper is exposed in the rest. And then etching, so we can get the patterns. The negative phase patterns can be realized by negative resist, negative film or positive photoresist.

Characteristics and Deposition Mechanism of ED membrane:

ED membrane can let the photosensitive polar material disperse in the electrolyte, as a decomposition system. Under the action of electric field, the photosensitive polar material will migrate to MLB that is as the electrode by charged groups, and electrochemical reaction will take place on the surface of the electrode, which is uniformly deposited on the electrode and formed. The characteristics of this membrane are as follows.

a)      Thin and high-density.

b)      Suitable for MLB production which has high requirements for patterns.

c)      Fine line resolution up to 0.025 mm.

d)     It can form the membrane with uniform thickness and is very tightly bonded to the electrode surface (even if there are pits, scratches, etc.), having strong and excellent adhesion.

e)      Short operation time, simple production process and low cost.

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