Overcoming micro scale residue is the core challenge to ensure the reliability of high-density interconnects in PCB (printed circuit board). The plasma glue remover, with its non-contact, high uniformity, and precise and controllable physical and chemical synergy, has become a key technology to solve this problem.
The main ways to crack it are reflected in the following three aspects:
1. Anisotropic etching and precise size control
High energy ions in plasma, driven by an electric field, can bombard the surface of the pore wall almost vertically. This directional bombardment causes the chemical reaction rate in the vertical direction to be much higher than that in the horizontal direction, thereby achieving anisotropic etching. This is particularly crucial for cleaning the adhesive residue at the bottom of deep micro blind holes or through holes. It can effectively remove residues while protecting the glass fiber and other substrates on the side walls of the holes from excessive erosion, maintaining the geometric shape and dimensional accuracy of the hole walls, and avoiding "over corrosion" or "side corrosion".
2. Deep synergy between physical bombardment and chemical reactions
The essence of plasma cleaning is the synergy of physical sputtering and chemical reactions.
Physical sputtering: High energy ions (such as Ar ⁺) collide directly with kinetic energy to "break" residual macromolecular colloids and sputter them out, especially for non-polar, cross-linked and dense stubborn residues.
Chemical reaction: Active free radicals (such as O ⁺, F ⁺) react chemically with organic residue, decomposing it into volatile small molecule gases such as CO ₂ and H ₂ O, which are then evacuated by a vacuum system. For example, oxygen plasma can efficiently oxidize hydrocarbons.
The physical action "breaks down" and the chemical action "decomposes", working together to ensure that the adhesive residue from the bottom of the hole to the wall, and even in the submicron gaps, is uniformly removed.
3. Fine tuned plasma control technology
Modern plasma debonding machines achieve "customized" removal of micron sized adhesive residue by precisely adjusting process parameters
Gas formula: using O ₂/CF ₄ or O ₂/Ar mixed gas. O ₂ is responsible for chemical oxidation, fluorine radicals generated by CF ₄ can enhance the etching of complex polymers, and Ar enhances physical bombardment. The proportion can be precisely adjusted according to the composition of the adhesive residue.
Power and pressure control: Lower pressure can increase plasma density and ion mean free path, enhancing anisotropy; The appropriate RF power controls the reaction activity and etching rate, achieving the best balance between efficient cleaning and substrate protection.
In summary, the plasma de gluing machine maintains the hole pattern through anisotropic etching, achieves deep cleaning through physical and chemical synergy, and is supplemented by refined process parameter control, fundamentally solving the inherent defects of residual, poor uniformity, and environmental pollution in traditional wet de gluing in micropores. It has become a part of high-density and high reliability PCB manufacturing.