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14 PCB007 MAGAZINE I MAY 2025 • Laser surface texturing: High-precision lasers create microstructures on copper for adhesion enhancement in semiconductor packaging and HDI PCBs. › Risks: Over-texturing can alter conduc- tivity and impact signal integrity; under- processing leads to poor adhesion and reliability issues. › Prevention: Use controlled laser power and scanning speed. Conduct electrical resistance measurements post-processing. Case Studies: Surface Preparation Failures and Solutions Case 1: Delamination in a multilayer RF PCB • Industry: Aerospace and defense • Material: PTFE-based substrate • Issue: Copper delamination aer thermal cycling due to poor adhesion • Solution: Implemented oxygen plasma treatment and silane coupling agents, eliminating delamination and increasing adhesion strength by 40% Case 2: Poor solder mask adhesion in HDI PCBs • Industry: Consumer electronics • Material: High-Tg FR-4 laminate • Issue: Solder mask peeling aer multiple reflow cycles due to inadequate microetch- ing and over-brushing • Solution: Optimized microetching and added plasma activation, reducing SMT rework rates by 90% Case 3: Electroless copper plating failure in vias • Industry: Automotive (ADAS Systems) • Material: Hybrid FR-4/PTFE PCB • Issue: Resin smear in vias caused plating voids, leading to intermittent electrical failures • Solution: Introduced a two-stage desmear- ing process and optimized electroless cop- per deposition, improving reliability and passing 1,000+ thermal shock cycles Case 4: Corrosion and solderability issue in medical PCBs • Industry: Medical Electronics • Material: Gold-plated PCB with poly- imide dielectric • Issue: Residual organic contaminants reacted with sterilization chemicals, caus- ing corrosion and solderability issues • Solution: Implemented ultrasonic cleaning and plasma pre-treatment, eliminating cor- rosion and improving solderability by 50% Environmental Impact of Surface Preparation While surface preparation is essential for PCB fabrication, some methods have signif- icant environmental implications. Changes cannot easily be made to maintain the high levels of performance and reliability required on many electronic products. Nonetheless, we remain mindful of less harmful alternatives as they are created, as well as the reality that we may be required to find alternate solutions Application Best Surface Prep Method Key Benefit General FR-4 PCBs Brushing + Micro-etching Removes oxidation, improves adhesion HDI, fine-line PCBs Plasma or chemical desmearing Prevents damage to small traces Inner layers Black oxide/alternative oxide Enhances resin adhesion in lamination RF, microwave PCBs Plasma or Microblasting Roughens PTFE for better adhesion High-speed Digital PCBs Silane Treatment Reduces signal loss Automotive PCBs Microetching + Plasma Desmearing Strong adhesion in harsh conditions Semiconductor PCBs Laser surface texturing Precise microstructuring for bonding Table 1: Best surface preparation method by laminate type