Fume Control for Conformal Coating PCBs [Ductless Spray Hoods]

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Conformal Coating

A highly recommended last step in the manufacturing process of developing printed circuit boards (PCBs) is conformal coating. Conformal coating is a protective film that is applied to PCBs to protect them from a variety of naturally-occurring and man-made environmental hazards, including moisture, chemicals, dust, corrosion, and extreme temperatures. This protective measure is especially important for sensitive applications, such as aerospace technology, automotive manufacturing, and data communications.

Conformal coating comes in a variety of material options, featured properties, and application methods. Types of conformal coating include Silicones, Acrylic, Epoxies, Polyurethanes, Paraxylylenes, and Fluorocarbon. They are also available in Solvent-Based, Water-Based, Solvent-less Silicones, and Solvent-less UV Curable options.

There are a variety of application methods for coating PCB boards with this protective membrane. These include, but are not limited to:

  • Spray Applications– in which conformal coating is available in an aerosol can for direct application. Automated machinery is also available for spraying PCBs.
  • Dip Applications- This technique can be done by hand or by automated equipment. PCBs are slowly submerged and removed from coating material.
  • Brush Applications– This method is typically done by hand by brushing on conformal coating from a pot.
  • Transfer Coating- To complete this method, operators fill a tool pot with coating and then place and attach the PCB to the top of the pot. Once the PCB is firmly attached, the entire unit is turned over so that the PCB becomes coated. The unit is then turned back over and the PCB is removed.

The Hazards of Conformal Coating

Because many popular conformal coatings contain large percentages of solvents, potential negative health effects should be considered when utilizing these materials. When personnel in this industry reach out to us with the need for fume extraction and air purification of conformal coating, one of the brands that is mentioned frequently is Chemtronic’s KonForm® SR.

Whenever a new conformal coating is introduced into your working environment, the Material Safety Data Sheet (MSDS) for that individual product should be read over thoroughly. When trying to improve air quality and limit inhalation of fumes and vapors of these products, a few key areas to look at on the MSDS are the following [as an example, we will look at the Chemtronic’s KonForm® MSDS (PDF)]:

Section 2 of this MSDS covers Composition/Information on Ingredients:
For Hazard Identification in relation to this product, take a look at Section 3, which provides an emergency overview and potential health effects via various routes of entry.

 

Because of the negative health effects that are possible by overexposure to many of these ingredients, exposure limits have been established by various health and safety organizations. You can find these exposure guidelines in Section 8:

TLV: Threshold Limit Value, PEL: Permissible Exposure Limit, STEL: Short Term Exposure Limit

You will also find Exposure Controls and Personal Protection Recommendations in Section 8.

As indicated above, “Good general ventilation should be sufficient to control airborne levels. Local exhaust ventilation may be necessary to control any air contaminants to within their TLVs (threshold limit values) during the use of this product. If vapor concentration exceeds TLV, use NIOSH approved organic vapor cartridge respirator […].”

Local Exhaust Ventilation: Ductless Spray Booths
One example of local exhaust ventilation that can be used with conformal coating applications (especially spray applications) is a benchtop Ductless Spray Booth. Ductless Spray Booths provide a negative-pressure enclosure that pulls airborne contaminants away from the operator’s breathing zone. These systems are equipped with a powerful fan situated on top of the hood that draws aerosol particulate and fumes through a triple-stage filtration system consisting of an internal spray filter, HEPA Filter [up to 99.97% efficient on particles 0.3 microns and larger], and Activated Carbon Filter. This multi-stage configuration is able to capture the visible overspray, small respirable particles, and chemical fumes found in conformal coat spray at a relatively high efficiency

Sentry Air Systems offers 30″, 40″, 50″, and 60″ wide Ductless Spray Booths. Custom Spray Booths are also available. Custom Metal Spray Booths are an additional option for applications that require ESD-hood material. ESD-safe trays [pictured below] are also available for easy clean-up.

30″ Wide Ductless Spray Booth shown above
Video Demonstration:
Want more information on Ductless Spray Hoods for Conformal Coating Applications?
Sentry Air Systems’ Applications Specialists are able to review your process and aid in finding the appropriate solution for your conformal coating fume controls needs.