What is a Conformal Coating by Humiseal Academy
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Wit this presentation you will learn what is a conformal coating, what does it, what types are there, how to select and how to test it.
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What is a Conformal Coating by Humiseal Academy
- 2. WWW.HUMISEAL.COM • What is a conformal coating? • What does it do? • Why coat? • What types are there? • How to select? • How to apply? • How to test? Coating Conformal
- 3. WWW.HUMISEAL.COM • A thin protective film that “conforms” to the varied profiles of an electronic circuit assembly. • A breathing membrane that will filter moisture and dirt to protect the assembly from environments. What is a Conformal Coating?Coating Conformal
- 4. WWW.HUMISEAL.COM Provide Protection From: • Insulation and Dielectric Failures • Moisture • Heat • Corrosion • Fungus • Dust, Conductive particles Why Coat? IMPROVED CIRCUIT RELIABILITY Coating Conformal
- 5. WWW.HUMISEAL.COM It should provide... • Good insulation • Good dielectric properties • Good moisture resistance • Good flexibility so as not to stress components... • Ability to be Repaired... What Does It Do?Coating Conformal
- 6. WWW.HUMISEAL.COM What Coating Types Are Available? Coating Type MIL Spec Thickness Acrylics 25-75µ (0.001 - 0.003”) Polyurethanes 25-75µ (0.001 - 0.003”) Epoxies 25-75µ (0.001 - 0.003”) Silicones 50-200µ (0.002 - 0.008”) Coating Conformal
- 7. WWW.HUMISEAL.COM Applicable Standards & Specifications – US MIL-I-46058C – IPC-CC-830B – UL - Underwriters Labs 746E Electrical Properties – Insulation resistance, dielectric constant Thermal Properties – Operating temperature range, thermal expansion (CTE) How To Select?Coating Conformal
- 8. WWW.HUMISEAL.COM 5 Strengths of Coating Type 5 Weaknesses of Cure Type ACRYLIC •Ease of rework •Simple drying process •Good moisture resistance •High fluorescence level •Ease of viscosity adjustment Solvent Evaporation •High VOC potential •Difficult to maintain viscosity •Requires close monitoring of solvent concentration, hence Creates a 2-part scenario •Flammability •High probability of reversion under temperature and humidity stress conditions Heat Cure •Cure is dependent on thickness •Component mass affects time and temperature of cure process •Susceptible to cure inhibition •Shrinkage (3% - 10%), potential for damaging fragile (e.g., glass) components •Should be used with caution for low temperature components UV Cure •Incomplete cure in shadowed areas •Pungent odour, potential skin irritant •Can become very brittle at higher temperature •Difficult to rework •Type of UV and intensity affect cure Acrylic Strengths and Weaknesses Coating Conformal
- 9. WWW.HUMISEAL.COM 5 Strengths of Coating Type 5 Weaknesses of Cure Type EPOXY •Useful to about 150oC [302oF] •Harder durometer, abrasion resistance •CTE closer to epoxy PCB substrate •Higher Tg •Good dielectric properties Solvent Evaporation •Higher chloride contamination potential •Process intensive, difficult to maintain viscosity, complex mix ratios •Potential for high stress during temperature cycling conditions •Difficult to rework •High probability of reversion under temperature and humidity stress conditions Heat Cure Cure is dependent on thickness Component mass affects time and temperature of cure process Selective coating quality (edge definition) could be impacted Shrinkage (3% - 10%), potential for damaging fragile (e.g., glass) components Should be used with caution for low temperature components UV Cure •Incomplete cure in shadowed areas •Pungent odour, potential skin irritant •Can become very brittle at higher temperature •Difficult to rework •Type of UV and intensity affect cure Catalyzed •Cure inhibition •Short work life •Contamination sensitive •Difficult to rework •Pungent odour Epoxy Strengths and Weaknesses Coating Conformal
- 10. WWW.HUMISEAL.COM 5 Strengths of Coating Type 5 Weaknesses of Cure Type POLYURETHANE •Good dielectric properties •Good moisture resistance •Solvent resistance •Less reversion potential •Abrasion resistance Solvent Evaporation •Moisture affects cure rate and desires properties •Long complete cure time (up to 30 days) •Health and safety concerns •Potential for high stress during temperature cycling conditions •High probability of reversion under temperature and humidity stress conditions Heat Cure •Cure is dependent on thickness •Component mass affects time and temperature of cure process •High VOC potential •Should be used with caution for low temperature components •Reacts violently with presence of water UV Cure •Incomplete cure in shadowed areas •Pungent odour, potential skin irritant •Can become very brittle at higher temperature •Difficult to rework •Type of UV and intensity affect cure Polyurethanes Strengths and Weaknesses Coating Conformal
- 11. WWW.HUMISEAL.COM 5 Strengths of Coating Type 5 Weaknesses of Cure Type SILICONES •Stable over wide temperature range (in general, -40oC to 200oC) [104oF to 392oF] •Flexible, provides dampening and impact protection •Good moisture, humidity, and UV/sun light resistance •High dielectric strength •Low surface energy to enable effective penetration under components 5 Weaknesses of Cure Type •Room Temperature Vulcanization (RTV) •Requires humidity (minimum 20% RH) to cure and only intermittent solvent resistance •Low abrasion resistance •Short pot life •TCE is -300-350 ppm/oC •If proper housekeeping is not followed, there is a potential for cross contamination UV Cure •Incomplete cure in shadowed areas •Potential skin irritant •Low abrasion resistance •Only intermittent solvent resistance •If proper housekeeping is not followed, there is a potential for cross contamination Catalyzed (Addition) •Low abrasion resistance •Potential for cure inhibition •Adhesion may be difficult •Only intermittent solvent resistance •If proper housekeeping is not followed, there is a potential for cross contamination Silicone Strengths and Weaknesses Coating Conformal
- 12. WWW.HUMISEAL.COM • Brushing • Dipping – Manual / Automated • Spraying – Aerosol / Manual / Automated • Flow-Coat – Automated How To Apply?Coating Conformal
- 13. WWW.HUMISEAL.COM • Best suited for repair and rework • Keep the brush “loaded” • Flow the coating - DO NOT PAINT! Brushing? BRUSH Coating Conformal Application
- 14. WWW.HUMISEAL.COM • Slow speed dip - < 30cm/min (12”/min) – Minimizes air entrapment under components • Slower Removal Rate - < 10cm/min (4”/min) – The slower the speed, the thinner the coating • ALWAYS dip board in vertical position, not horizontal Dip DIP Coating Conformal Application
- 15. WWW.HUMISEAL.COM • Coating penetrates under components and behind component legs • Coating is applied to both sides simultaneously • Coating thickness controlled by dipping speed & viscosity control • Can be done by hand for small assemblies but best done by machine Dip DIP Coating Conformal Application
- 16. WWW.HUMISEAL.COM • Single Dip – Possibility of Sharp Edges being exposed • Double Dip Solves this Problem “Double Dipping”Coating Conformal DIP Application
- 17. WWW.HUMISEAL.COM • Controls dip speed in and out • Maximizes coverage • Reduces waste • Minimizes Evaporation of Coating Bath Automated DippingCoating Conformal DIP Application
- 18. WWW.HUMISEAL.COM • Coating is thinned with solvent for application • Hand Spray • HumiSeal Aerosol products • Automated Equipment – Asymtek / Nordson – PVA Spray?Coating Conformal SPRAY Application
- 19. WWW.HUMISEAL.COM • Remember cured coating thickness should be 25 - 75 (0.001-0.003”) and material is diluted • Need multiple passes each at 90 degrees and multiple coats, 2 to 3 minimum • Always spray assembly in horizontal with spray gun at ~45 degree angle to board surface Spraying – Aerosol/HandCoating Conformal SPRAY Application
- 20. WWW.HUMISEAL.COM • Relatively Simple • 2-Part Materials may be used • Better Tip and Edge Coverage • Reduced Masking Spraying – Hand/AutoCoating Conformal SPRAY Application
- 21. WWW.HUMISEAL.COM • 1B73, 1B31, 1B73 EPA, 1A33 and 1A27 • Packaged in 12-oz cans • Good for small users and rework • Lower solids content than liquid products AEROSOLSCoating Conformal SPRAY Application
- 25. WWW.HUMISEAL.COM • Visual Inspection With UV Light • Check Coating Uniformity How To Test?Coating Conformal
- 26. WWW.HUMISEAL.COM – Widest product selection – > 50 years experience – Greatest pool of technical knowledge – ISO 9001 Registered – Mil-I-46058C, IPC-CC-830 and UL746E compliant products – VOC compliant materials HumiSeal Conformal CoatingsCoating Conformal
- 27. WWW.HUMISEAL.COM • EASY TO APPLY • Most forgiving of contamination • Dry at room temperatures • Have desirable electrical and physical properties • Fungus resistant • Long pot life • No exotherm during drying- heat sensitive components • Does not shrink • EASY TO REPAIR • VOC and VOC HAPS-free versions available HumiSeal Acrylic (AR) Products Coating Conformal
- 28. WWW.HUMISEAL.COM • Excellent chemical and humidity resistance • Outstanding dielectric properties for extended periods • Excellent chemical resistance • Available as single - or two-component • Variety of cure types • Moderately repairable – Chemical strippers – Heat • VOC and VOC HAPS-free versions available HumiSeal Urethane (UR) Products Coating Conformal
- 29. WWW.HUMISEAL.COM • Excellent for high temperature service • Good thermal endurance – heat generating devices • Humidity and corrosion resistance • One component, 100% solids – no VOC issues • Thermal or moisture cure • Lower abrasion resistance- softer • High CTE • Mechanically repairable – Not solvent-soluble / Do not vaporize with heat – New Silicone Digesters HumiSeal Silicone (SR) Products Coating Conformal
- 30. WWW.HUMISEAL.COM • Two components: 2A53A + 2A53B • High abrasion and chemical resistance • Might be considered “indestructible” • Good electrical properties • Good component anchoring • Very Difficult to Repair – Hard to physically remove – Not removed by solvent – Chemical strippers will attack substrates HumiSeal Epoxy (ER) 2A53 Coating Conformal
- 31. WWW.HUMISEAL.COM • 1B51 Series (Synthetic Rubber) – High flexibility – Excellent electrical properties – High humidity & corrosion resistance – Good thermal stability, low outgassing – High cohesive strength – tough – Low CTE – Stabile Modulus at lower temps – Must be repaired mechanically • Not solvent soluble / requires aggressive stripper • Does not vaporize with heatHumiSeal 1B51 Series (Synthetic Rubber) Coating Conformal
- 32. WWW.HUMISEAL.COM HumiSeal Ancillary Products • TempSeal • Strippers • Thinners Coating Conformal
- 33. WWW.HUMISEAL.COM Conformal Coating is a Simple Process 1. Clean 2. Masking 3. Coating Application 4. Dry / Cure 5. Remove Masking • But if product is not processed correctly…Troubleshooting Coating Conformal
- 34. WWW.HUMISEAL.COM • Poor surface cleanliness is most common cause of coating problems – Adhesion loss – Electrical failures – Coating voids • IPC specifications recommend ionic cleanliness level of < 1.5 g/cm2 NaCl equivalence Troubleshooting Surface Cleanliness Coating Conformal
- 35. WWW.HUMISEAL.COM • Need to keep within recommended ranges • Too Thick – Incomplete drying / solvent entrapment – Bubbles – Longer cure times – Shrinking or cracking – Decreased coating properties • Too Thin – Inadequate Protection! Troubleshooting Coating Thickness Coating Conformal