PCB board processing special process

1. Additive Process refers to the surface of the non-conductive substrate. With the assistance of an additional resist, a direct growth process of the local conductor circuit is carried out using a chemical copper layer (refer to page 62 of the 47th issue of the Circuit Board Information Magazine for detailed information). The additive method used in circuit boards can be categorized into full addition, half addition, and partial addition.

2. Backpanels, Backplanes

Backpanels, also known as backplanes, are circuit boards with a thicker thickness (such as 0.093″ or 0.125″), specifically designed for interconnecting with other boards. The method involves initially inserting a multi-pin connector (Connector) into the tight through hole without soldering it. Subsequently, wires are meticulously connected one by one in a winding manner to each guide pin of the connector passing through the board. This allows for the insertion of a general circuit board into the connector. Due to the unique nature of these boards, where through holes cannot be soldered but instead the hole wall and guide pins are directly clamped for use, stringent quality and aperture requirements are necessary. Consequently, the order quantities for such specialized boards are limited, with many general circuit board manufacturers hesitant to accept such orders. Consequently, production of backpanels has become predominantly specialized, particularly in the United States.

3. Build Up Process

The Build Up Process represents a novel approach in thin multi-layer board fabrication. Originating from IBM’s SLC process, initiated at its Yasu factory in Japan in 1989, this method builds upon traditional double-sided boards. Initially, the outer surface of the board is entirely coated with a liquid photosensitive precursor such as Probmer 52. Following partial hardening and photosensitive resolution, shallow “photo-vias” (Photo-Via) are created, facilitating communication with the next bottom layer. Through comprehensive electroplating of the conductor layer with copper, followed by line imaging and etching, new wires and buried or blind holes interconnected with the bottom layer are achieved. Iteratively adding layers in this manner yields multi-layer boards with the required number of layers. This process eliminates the need for costly mechanical drilling and allows for reducing hole diameters to less than 10 mil. Over the past 5-6 years, various innovative multi-layer board technologies have emerged, departing from traditional layer addition methods. Under the continuous advocacy of the US, Japan, and Europe, these Build Up Processes have gained prominence, resulting in the introduction of over ten products. Apart from the aforementioned “photosensitive hole forming,” alternative techniques such as alkaline chemical bite hole, Laser Ablation, and Plasma Etching for organic plates post copper skin removal have been developed. Furthermore, the utilization of “Resin Coated Copper Foil,” coated with semi-hardening resin, facilitates the creation of finer, denser, smaller, and thinner multilayer boards through Sequential Lamination. In the foreseeable future, the realm of diversified personal electronic products will be dominated by these truly thin, short, and multi-layer boards.

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