Desmear Solution for PCB Resin Substrate Smear Removal
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Solution Overview
Problem
Existing desmear solutions for printed circuit boards excessively roughen the resin substrate, leading to weakened strength and adhesion of the plating film, while also producing excessive hexavalent manganese, which requires large anode areas for recycling and reduces etching rates.
Innovation Solution
A desmear solution with a permanganate concentration of 0.2 to 0.4 mol/L and a higher concentration of alkali metal hydroxide, maintaining a molar ratio of 1:5 to 1:20, effectively removes smear without excessive etching, improving adhesion and controlling resin loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a desmear solution with high permanganate concentration (0.4 mol/L) is used to remove smear, then smear removal effect is improved, but the resin substrate surface is excessively roughened and strength is lowered
Solution Approach 1:
The patent changes the concentration parameters of the desmear solution components. Specifically, it uses permanganate at 0.2-0.4 mol/L (optimal range) and controls the mole ratio of permanganate to alkali metal hydroxide at 1:5 to 1:20. This parameter optimization ensures sufficient smear removal while preventing excessive etching that would weaken the resin substrate.
Solution Approach 2:
The patent creates different chemical environments for different purposes: the permanganate provides strong oxidizing power for smear removal, while the high concentration of alkali metal hydroxide (in 1:5 to 1:20 ratio) creates a controlled etching environment that generates appropriate surface roughness for plating film adhesion without excessive resin removal.
2Reliability
If a desmear solution with high permanganate concentration is used to remove smear, then smear removal effect is improved, but adhesion of plating film is lowered due to excessive roughening
Solution Approach 1:
The patent optimizes the concentration parameters to achieve the right balance: permanganate at 0.2-0.4 mol/L for smear removal, with alkali metal hydroxide in a 1:5 to 1:20 mole ratio. This creates controlled surface roughness (not excessive) that provides mechanical interlocking for plating film adhesion while maintaining resin substrate integrity.
Solution Approach 2:
The patent applies partial action by using a controlled amount of etching (not excessive) through the optimized alkali metal hydroxide concentration. This partial etching creates sufficient surface roughness for adhesion without over-etching that would damage the substrate and reduce plating film bonding area.
3Productivity
If a desmear solution with high permanganate concentration is used, then etching rate is improved, but excessive hexavalent manganese is produced requiring large anode area for recycling
Solution Approach 1:
The patent changes the permanganate concentration to an optimal range of 0.2-0.4 mol/L and controls the alkali metal hydroxide concentration at a higher level with a 1:5 to 1:20 mole ratio. This parameter optimization maintains effective etching rate while reducing the excessive formation of hexavalent manganese, thereby decreasing the anode area required for electrolytic oxidation recycling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures effective smear removal and appropriate surface roughness, reducing resin etching and hexavalent manganese production, thus enhancing the strength and adhesion of the resin substrate to the plating film while minimizing excessive roughening and etching rates.
Implementation Method 1
a permanganate contained in a desmear solution reacts with resin of a substrate, whereby heptavalent manganese is reduced to hexavalent manganese
Implementation Method 2
the hexavalent manganese is oxidized to heptavalent manganese by electrolytic oxidation to reproduce and recycle a permanganate
Data Source
Figure 1A~1B
AI summary
The present invention provides a desmear solution and a desmear method using said desmear solution, the desmear solution being capable of certainly removing a smear inside a non-through hole formed in a resin substrate and also capable of forming a plating film excellent in adhesion without excessive roughening of a surface of the resin substrate. The present invention uses the desmear solution containing a permanganate having a concentration of 0.2 to 0.4 mol/L and an alkali metal hydroxide and having a molar concentration ratio of said permanganate to said alkali metal hydroxide of 1:5 to 1:20.