Introduction:

The rapid development of PCB technology has introduced new challenges and higher demands, such as increased density, higher speeds, and miniaturization. These advances have made traditional manufacturing techniques inadequate for meeting the needs of modern PCBs.

Traditional Multilayer PCB Manufacturing Technology (Outer Layer Patterns Example):

After fabricating the inner patterns of a multilayer PCB (MLB), the board undergoes a series of processes including lamination, drilling, and PTH. Once these steps are complete, the process of creating the outer patterns begins. There are two main traditional manufacturing methods:

• Pattern Plating and Etching

After the PTH process, both the holes and the surface of the PCB are covered with copper. The surface of the MLB is first coated with a photoresist layer, which is exposed to light at a specific wavelength to polymerize the photoresist that isn’t covered by the patterns. The unexposed photoresist is then removed, and the surface is developed to create the desired pattern. Following this, electrical plating is performed to thicken the copper layer, ensuring the copper thickness on the hole walls exceeds 25µm. A Pb/Sn alloy is electroplated onto the copper layer for protection, followed by etching to reveal the surface conductive pattern.

• Tenting and Etching

In this method, the MLB surface is coated with a photoresist layer, which is exposed and developed in a similar manner, but the photoresist covers the lines and holes while exposing the copper areas. The exposed copper is then etched away, leaving behind the desired patterns. This method can utilize negative resist, negative films, or positive photoresists to achieve the negative phase patterns.

Characteristics and Deposition Mechanism of ED Membranes:

ED membranes allow photosensitive polar materials to disperse in the electrolyte, forming a decomposition system. When an electric field is applied, the photosensitive polar material migrates to the MLB, acting as the electrode. An electrochemical reaction occurs on the electrode’s surface, resulting in a uniform deposition that forms the membrane. The characteristics of this membrane are:

• Thin and high-density.
• Ideal for MLB production with strict pattern requirements.
• Fine line resolution down to 0.025 mm.
• Uniform thickness with strong adhesion, even on surfaces with pits, scratches, or other imperfections.
• Short process time, simple production, and cost-efficient.

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