Conformal Coating Training

Coating Conformal 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 What is a Conformal Coating? 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.

Coating Conformal Why Coat? Provide Protection From: Insulation and Dielectric Failures Moisture Heat Corrosion Fungus Dust, Conductive particles IMPROVED CIRCUIT RELIABILITY

Coating Conformal What Does It Do? It should provide... 4/27/2017 Conformal Coating What Does It Do? It should provide... Good insulation Good dielectric properties Good moisture resistance Good flexibility so as not to stress components... Ability to be Repaired... 5

Coating Conformal What Coating Types Are Available? Coating Type MIL Spec Thickness Acrylics 25-75µ (0.001 - 0.003”) Polyurethanes Epoxies Silicones 50-200µ (0.002 - 0.008”)

Coating Conformal How To Select? Applicable Standards & Specifications 4/27/2017 Conformal Coating How To Select? 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) 7

Coating Conformal Acrylic Strengths and Weaknesses 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 Epoxy Strengths and Weaknesses 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 Type of UV and intensity affect cure Catalyzed Cure inhibition Short work life Contamination sensitive Pungent odour Epoxy Strengths and Weaknesses

Coating Conformal Polyurethanes Strengths and Weaknesses 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 Silicone Strengths and Weaknesses 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 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 Only intermittent solvent resistance Catalyzed (Addition) Potential for cure inhibition Adhesion may be difficult Silicone Strengths and Weaknesses

Coating Conformal How To Apply? Brushing Dipping – Manual / Automated Spraying – Aerosol / Manual / Automated Flow-Coat – Automated

Coating BRUSH Application Conformal Brushing? Best suited for repair and rework Keep the brush “loaded” Flow the coating - DO NOT PAINT! BRUSH Application

Coating DIP Application Conformal Dip 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 Application

Coating DIP Application Conformal Dip 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 Application

Coating DIP Application Conformal “Double Dipping” Single Dip – Possibility of Sharp Edges being exposed Double Dip Solves this Problem

Coating DIP Application Conformal Automated Dipping Controls dip speed in and out Maximizes coverage Reduces waste Minimizes Evaporation of Coating Bath DIP Application

Coating SPRAY Application Conformal Spray? Coating is thinned with solvent for application Hand Spray HumiSeal Aerosol products Automated Equipment Asymtek / Nordson PVA SPRAY Application

Coating SPRAY Application Conformal Spraying – Aerosol/Hand 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 SPRAY Application

Coating SPRAY Application Conformal Spraying – Hand/Auto Relatively Simple 2-Part Materials may be used Better Tip and Edge Coverage Reduced Masking SPRAY Application

Coating SPRAY Application Conformal AEROSOLS 1B73, 1B15H, 1A33 and 1A27 Packaged in 12-oz cans Good for small users and rework Lower solids content than liquid products SPRAY Application

Conformal Coating Selective Spray Equipment SPRAY Application

Conformal Coating Automated Atomized Spray SPRAY Application

Conformal Coating FLOW Coating

Coating Conformal How To Test? Visual Inspection With UV Light Check Coating Uniformity

Coating Conformal Humiseal Conformal Coatings 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

Coating HumiSeal Acrylic (AR) Products Conformal 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 HumiSeal Urethane (UR) Products Conformal 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 HumiSeal Silicone (SR) Products Conformal 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 HumiSeal Epoxy (ER) 2A53 Conformal 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 HumiSeal 1B51 Series (Synthetic Rubber) Conformal 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 heat HumiSeal 1B51 Series (Synthetic Rubber)

Coating HumiSeal Ancillary Products Conformal TempSeal Strippers Thinners HumiSeal Ancillary Products

Coating Troubleshooting Conformal Conformal Coating is a Simple Process Clean Masking Coating Application Dry / Cure Remove Masking But if product is not processed correctly… Troubleshooting

Coating Troubleshooting Conformal Surface Cleanliness 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 Troubleshooting Conformal Coating Thickness 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