Via-in-Pad Resin Plugging in High-Voltage PCB

This Project is about a 4-layer high-voltage PCB with via-in pad structure for industrial control applications which recently delivered by KnownPCB. In this multilayer high-voltage board, the via-in-pad construction is applied in the pad areas of key components and we used resin plugging process to ensure superior pad flatness and long-term structural stability.

For such high-voltage circuit board design, via manufacturing technology affects both soldering quality and the long-term reliability of the entire board in high-voltage operating environments.

The parameters for this custom high-voltage PCB:

	Base Material	S1600
	Layers	4
	Dimensions	90*65
	PCB Thickness	1.6 mm
	Board Solder Mask Color	Red
	Silkscreen	White
	Surface Finish	ENIG 2U''

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Via-in-Pad Resin Plugging in High-Voltage PCB

Why the via-in-pad is critical for high-voltage PCB design?

For via-in-pad structure, vias are placed in the center of pads. Therefore, if there is any improper via processing during this high-voltage board manufacturing, when the circuit board is soldering through reflow process, molth solder will easily flow into the via holes, which can leads to typical assembly failures such as solder voids, dry joints and pad collapse.

For this multilayer high-voltage PCB, the density and structural stability of internal via filling also influence the long-term reliability

Main Risks of improper Via Processing

The risks of via-in-pad constructions are primarily reflected in three dimensions:

1. Soldering issues: solder loss, dry joints and solder voids.

2. Pad flatness risks: Pad depression or uneven surface, which affects mounting stability of SMT placement.

3. Filling defects: insufficient filling, shrinkage, or internal void risk

Since the main challenge of this 4-layer high-voltage PCB is from the soldering and structural risks which caused by improper via treatment, thus, the key point for the solution of manufacturing is:

Improve the compactness of via filling and the surface flatness of pads, in the meanwhile ensure structural thermal stability.

Solution for this multilayer high-voltage board

To solve this challenge, KnownPCB adopted the via-in-pad resin plugging process with stable manufacturing quality through the control of key process parameters:

1.We achieve a filling rate of nearly 100% to ensure the internal structure of vias is dense and does not have obvious voids.

2. By controlling the surface flatness of the pad area within ≤20μm, we guarantee the SMT stability for this high-voltage board.

3. we optimized the resin curing process, and reduce the risk of pad depression caused by material shrinkage.

Through KnownPCB's optimized manufacturing control of via processing technology, this 4-layer high-voltage PCB with via-in-pad resin plugging has achieved stable soldering performance and reliable structural consistency in the via-in-pad areas.

While reducing the risk of soldering defects, the entire board maintains excellent long-term reliability in high-voltage application environments, which can meet the requirements of mass assembly and stable operation.