In the process of PCBA patch processing, the design of PCB hole plates and solder masks is a crucial aspect. Next, we will delve into the processes of these two elements to understand PCB board and PCBA processing.

1. Orifice Plate Design in PCB Processing

The orifice plate design encompasses various types of plates with both metallized and non-metallized holes, all of which are linked to the PCB’s processing capacity. During PCB production, the expansion and contraction of films and materials, as well as the varying behaviors of materials during pressing, can lead to misalignments in the patterns across layers. To ensure optimal interconnection of these patterns, the width of the pad ring must account for alignment tolerances, effective insulation gaps, and reliability. This necessity is reflected in the precise control of pad ring width in the design.

(1) The metalized hole pad should be equal to or greater than 5 mils.

(2) The width of the insulation ring is typically 10 mils.

(3) The anti-pad ring width on the outer layer of the metallized hole should be at least 6 mils, mainly due to solder mask requirements.

(4) The anti-pad ring width in the inner layer of the metallized hole should be at least 8 mils, considering insulation gap requirements.

(5) The anti-pad ring width for non-metallized holes is generally designed to be 12 mils.

Regarding solder mask design in PCB processing, the minimum solder mask gap, bridge width, and cover expansion size depend on the solder mask pattern transfer method, surface treatment, and copper thickness. For precise solder mask design, it’s essential to consult the PCB manufacturer.

(1) With 1 OZ copper thickness, the solder mask gap should be at least 0.08 mm (3 mils).

(2) With 1 OZ copper thickness, the solder mask bridge width should be at least 0.10 mm (4 mils). Due to the lm-Sn solution’s effect on some solder resists, a moderate increase in the bridge width is necessary when using lm-Sn surface treatment, with a minimum of 0.125 mm (5 mils).

(3) With 1 OZ copper thickness, the minimum expansion size of the conductor Tm cover should be at least 0.08 mm (3 mils).

The solder mask design for via holes is crucial for manufacturability in PCBA processing, with plug holes depending on the process path and via layout.

(1) The three main methods for solder mask of via holes are: plug hole (including half plug and full plug), open small window, and open full window.

(2) For BGA dog bone connection via hole solder mask, a plug hole design is preferred:

1. It minimizes bridging due to solder mask offset during BGA reflow soldering.

2. If the lower board surface of the BGA passes directly through the wave crest, it reduces solder emergence during wave soldering, enhancing reliability by preventing remelting of the spot.