Conformal coating strippers are chemical products that are specifically designed and used for removing conformal coatings applied on printed circuit boards (PCBs). Conformal coatings are insulative and protective coatings applied on the surface of PCBs and electronic assemblies to protect them from various environmental factors like moisture, dust, salt spray and chemical contamination. When PCBs need repair or rework after the application of conformal coatings, specialized strippers are required to safely and effectively remove these protective coatings without causing any damage to the underlying components and circuitry.
Types of Conformal Coating Strippers
There are different types of strippers available depending on the type of coating that needs to be removed and the substrate material. Some of the commonly used conformal coating strippers include:
Acetone-based strippers: Acetone is a very effective and common solvent used for removing silicone and polyurethane Conformal Coating Stripper. It dissolves these coatings quickly without being too aggressive on component materials like plastics. However, it needs to be used carefully as prolonged exposure can damage some substrates.
Methylene chloride-based strippers: Strippers containing methylene chloride work very well for removing epoxy coatings. It has excellent solvency power but is a hazardous chemical and its use requires proper protective equipment and ventilation.
Alcohol-based strippers: Isopropyl alcohol (IPA) and other alcohol-based formulations work as mild strippers for light duty tasks. They are generally safer to use compared to chlorinated solvents but may require multiple applications for complete removal of coatings.
Amine-based strippers: These strippers containing reactive amine components are suited for stripping imide and polyimide coatings. They have good penetrating ability but their fumes can be noxious.
Unique formulation strippers: For specialized applications, there are conformal coating strippers available with formulations tailored to safely remove specific coating chemistries like acrylics, fluoropolymers, etc. without damaging components.
Stripping Process
The general process of stripping conformal coatings using chemical strippers involves:
1. Application of stripper: The stripper is applied using a small brush or swab directly onto the coated area. It is important to fully saturate the coating.
2. Dwell time: Allow sufficient time, usually 5-10 minutes, for the stripper to penetrate and soften the protective coating. This dwell time varies depending on type of stripper and coating.
3. Removal: Once the solvent has sufficiently broken down the bond between coating and substrate, the softened coating can be removed using a scraper or swab. Force should not be exerted to avoid component damage.
4. Rinsing: The stripped area needs to be thoroughly rinsed with fresh solvent like IPA to neutralize any residue of stripping chemicals and coating fragments. This avoids potential conductivity issues.
5. Inspection: The stripped surfaces are then inspected under a microscope to ensure complete removal without leaving any traces of coating, contaminants or affecting the substrate. If required, further stripping/rinsing steps are performed.
6. Ventilation: Adequate ventilation and personal protective equipment (PPE) like gloves, goggles etc. must be used while stripping to avoid exposure to vapours of stripping chemicals which can have adverse health effects.
Safety Considerations
Handling conformal coating strippers requires taking necessary precautions to prevent risks to health, equipment and environment:
– Select appropriate stripper chemically compatible with substrate and easily removable residues.
– Work in a well-ventilated area and use exhaustion systems to prevent inhalation of vapors which may be toxic.
– Wear gloves, masks, goggles as per Safety Data Sheet (SDS) of material to avoid direct contact.
– Never perform stripping near open flames or equipment with powered-on circuits due to fire/shock hazards.
– Have emergency showers/eye wash stations ready in case of accidental exposure and know first-aid steps.
– Store and dispose of used stripper as per environmental regulations to prevent groundwater contamination.
Advances in Coating Removal Technology
With the miniaturization of electronics, there is increased focus on developing more environmental-friendly and component-safe stripping methods:
– Plasma ashing uses ionized gas plasma to etch off coatings at lower temperatures than normal stripping without using harmful chemicals.
– Laser ablation employs short laser pulses to remove very small areas of coating precisely with minimal collateral damage.
– Water-based and solid-phase stripper formulations reduce volatility and toxicity compared to solvent-based products.
– In-situ stripping techniques are being researched where coatings can be removed from assemblies without disassembly using chemicals, plasma or other means.
selecting the appropriate conformal coating stripper based on the coated substrate material and taking necessary safety precautions during the stripping process is crucial. Advances aim at creating more sustainable and component-gentle stripping alternatives to traditional solvent-based methods. Proper coating removal enables successful rework of electronic circuitry without compromising reliability.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it