What is PTH Flash plating

PTH Flash plating is a key process in the manufacturing process of PCB (printed circuit board). Its main purpose and function is to deposit a thin layer of chemical copper on the non-conductive hole wall substrate that has been drilled by chemical methods, so as to serve as the base for the subsequent electroplated copper. The following is a detailed explanation of flash copper plating:

Purpose and function of PTH flash plating
Establishing a conductive layer: Establishing a dense and firm layer of copper metal as a conductor on the insulating hole wall of the PCB board, so that the signal can be conducted between the layers.
As a plating base: This thin layer of chemical copper provides a uniform and conductive base for the subsequent electroplated copper, ensuring the quality and uniformity of the electroplated layer.
Process flow of PTH flash plating

• Deburring: Before copper plating, after the PCB substrate undergoes the drilling process, burrs are prone to form on the hole edge and inner hole wall, which need to be removed mechanically to prevent the burrs from affecting the quality of subsequent copper plating and electroplating.
• Alkaline degreasing: removes oil stains, fingerprints, oxides and dust in the hole on the board surface, and adjusts the polarity of the hole wall substrate (adjusts the hole wall from negative charge to positive charge) to facilitate the subsequent adsorption of colloidal palladium.
• Roughening (micro-etching): slightly corrodes the board surface to increase the roughness and surface area of ​​the board surface, and improve the adhesion and bonding force of the subsequent copper layer.
• Pre-impregnation, activation, and degumming: prepare for the subsequent copper deposition process through a series of chemical treatments.
• Copper deposition: deposit a thin layer of chemical copper on the hole wall and the board surface as a base for subsequent electroplated copper. The thickness of conventional thin copper deposition is generally about 0.5μm.
• Acid immersion: provide an acidic environment for the subsequent electroplating process to ensure the quality and uniformity of the electroplated layer.

Advantages of PTH flash plating
Increase peeling resistance: Copper deposition uses activated palladium as the hole wall copper bonding medium layer, and embeds copper ions into the hole wall to firmly connect them to the hole wall resin and the inner copper layer.
High temperature resistance and stability: PCB boards produced by copper plating process can continue to operate and ensure smooth power supply in high temperature (such as 288°C) and low temperature (-25°C) environments.
Notes

1. The copper plating process is crucial to the quality of PCB boards. The control of process parameters needs to be precise, otherwise it is easy to cause quality problems such as hole wall voids.
2. The deburring and alkaline degreasing processes before copper plating need to be strictly implemented to ensure the quality of copper plating and electroplating.
3. Compared with the conductive glue process, the copper plating process is more expensive, but it has higher reliability and stability, and is suitable for the production of PCB boards with higher quality requirements.