Conformal Coating Electronics and Safety.

29 July 2015
Conformal Coating Electronics and Safety.

In this article, Scott Snell - Sales Manager Purex USA discusses Conformal Coating Materials and the need for adequate control of the hazardous gases and vapours they release into the workplace during processing in the electronics industry. Also the solution to this problem, delivered by Purex Fume Extraction Systems.

Scott Snell - Sales Manager Purex USA. Illinois, USA, 29/07/15
 
Conformal Coating Materials are omnipresent in electronic manufacturing processes, as they are easy to obtain and work with, are inexpensive and highly effective at protecting sensitive electronic devices from environmental stresses.
 
Some known hazardous materials often presented to the workplace by these conformal coating substrates are; Toluene, Benzene, Methyl Ethyl Keytone, Acrylic Polymers, Etc.
 
Recognising the above problem of hazardous materials; OSHA has recommended the following course of control. (https://www.osha.gov/SLTC/etools/safetyhealth/comp3.html): Excerpt:

 
Continually review the work environment and work practices to control or prevent workplace hazards.

 Some ways to prevent and control hazards are:

  • Regularly and thoroughly maintain equipment
  • Ensure that hazard correction procedures are in place
  • Ensure that everyone knows how to use and maintain personal protective equipment
  • Make sure that everyone understands and follows safe work procedures
  • Ensure that, when needed, there is a medical program tailored to your facility to help prevent workplace hazards and exposures

After detection, all current and potential hazards must be prevented, corrected or controlled. Systems used to prevent and control hazards include:

  • Engineering Controls
  • Safe Work Practices
  • Administrative Controls
  • Personal Protective Equipment (PPE)
  • Systems to Track Hazard Correction
  • Preventive Maintenance Systems
  • Emergency Preparation
  • Medical Programs
 
Engineering Controls
 
The first and best strategy is to control the hazard at its source. Engineering controls do this, unlike other controls that generally focus on the employee exposed to the hazard. The basic concept behind engineering controls is that, to the extent feasible, the work environment and the job itself should be designed to eliminate hazards or reduce exposure to hazards.

Engineering controls can be simple in some cases. They are based on the following principles:

  • If feasible, design the facility, equipment, or process to remove the hazard or substitute something that is not hazardous.
  • If removal is not feasible, enclose the hazard to prevent exposure in normal operations.
  • Where complete enclosure is not feasible, establish barriers or local ventilation to reduce exposure to the hazard in normal operations.
 
Purex Solution
 
An 800 Purex Fume Extractor for Conformal Coating SystemsMore often than not, it is not feasible to remove the hazardous materials from conformal coating process. Also, facilities are often designed without the intent to ever have a conformal coating process in the first place and it may not be feasible to vent hazardous chemicals to the atmosphere. 
 
Most conformal coating machines are however designed to “Enclose the Hazard” and allow for safe ventilation in and out of the process.
 
Purex Fume Extraction (such as the 800 unit pictured right), provide a solution in the form of a “Local Ventilation” device as an engineering control that does not harm the process and usually does not require ventilation to the atmosphere. 
 
Purex chemical filters are designed to remove gaseous and vaporous contaminants from the extract air-stream. The chemical element’s main body casing is constructed from a galvanised steel frame using a polyurethane adhesive which is then fastened and sealed into an aluminium or folded galvanised steel casing with silicone sealant.
 
The chemical itself consists of a bed of activated carbon blends in loose pellet form. There is a pad of polyester material on each side of the carbon bed to prevent emission of carbon dust. The chemical element removes all gases and vaporous contaminants which have boiling points greater than 60°C.
 
As a further engineering control Purex units employ a fume monitoring unit (FMU) that will continually look for contamination in return air quality from the conformal coating process. 
 
The FMUs used Purex machines are designed to detect the presence of a wide range of gaseous and vaporous contaminants. The basic mode of operation is that a boundary layer of oxygen molecules is created when the surface temperature of a layer of an oxide of tin is raised by a small heating element. The resistance of this sensor surface is converted electronically to a representative voltage. When molecules of contaminant gases arrive on the sensor surface, the resistance varies and hence the output voltage varies. This is amplified and visually indicated on the control panel. When the output voltage exceeds a pre-set value, a warning is displayed with a visual and audible alarm. Therefore advising the operator that new filters need to be installed.
 
Conformal Coating PCB
 
A coated PCB is inspected above.
 
Purex gas sensors will detect all but a small number of gases with a high degree of sensitivity and are essential where adsorptive type chemical filters are used to purify airflows which are to be returned to the workplace
 
Common contaminants and/or compounds that can and need to be captured by our standard activated carbon filters in the conformal coating process (and others) are as follows:
 
  • acetic acid  
  • acetic anhydride  
  • acetonitrile  
  • acids (organic)  
  • acrolein  
  • acrylic acid  
  • acrylonitrile  
  • acetone    
  • alcohol  
  • aldehydes  
  • aliphatic hydrocarbons  
  • allyl alcohol  
  • amyl actetate  
  • amyl alcohol  
  • amylene  
  • aniline  
  • aromatic hydrocarbons  
  • ashphalt fumes  
  • benzene  
  • Benzopyrene  
  • bromine  
  • butadiene  
  • butanol  
  • butyl acetate  
  • butyl alcohol  
  • butyl cellosolve  
  • butyl chloride  
  • butyl ether  
  • butyraldehyde  
  • butyric acid  
  • camphor  
  • caprylic acid  
  • carbon disulphide  
  • carbon tetrachloride  
  • carbonyl sulphide  
  • cellosolve (ethyl glycol)  
  • chlorobutadiene  
  • chlorine  
  • chlorobenzene  
  • chloroethene  
  • chloroform  
  • chloronitropropane  
  • chloropicrin  
  • chloropropane  
  • corrosive gases  
  • creosote  
  • cresol  
  • crontonaldehyde  
  • cumene  
  • cyclohexane  
  • cyclohexanol  
  • cyclohexanone  
  • dibromoethane  
  • dichlorodifluoromethane  
  • dichlorobenzene  
  • dichloroethane  
  • dichloroethylene  
  • dichloroethylether
  • dichloromonofluoromethane
  • dichloronitroethane  
  • dichloropropane  
  • dichlorotetrafluoroethane  
  • diethyl amine  
  • diethyl keytone  
  • dimethylaniline  
  • dimethylsuphate  
  • dioxane  
  • dipentane  
  • dipropylketone  
  • epichlorhydrin  
  • esters  
  • ethanol  
  • ethers  
  • ethyl acetate  
  • ethyl acrylate  
  • ethyl alcohol  
  • ethyl amine  
  • ethyl benzene  
  • ethyl bromide  
  • ethyl chloride  
  • ethyl ether  
  • ethyl formate  
  • ethyl silicate  
  • ethylene chlorohydrin  
  • ethylene dichloride  
  • ethylene oxide  
  • eucalyptole  
  • fluorotrichloromethane  
  • formaldehyde  
  • formic acid  
  • freons  
  • glutaraldehyde  
  • halogens  
  • heptane  
  • heptanol  
  • heptene  
  • hexane  
  • hexanol  
  • hexylene (1-hexene)  
  • hexyne (butyl acetylene)  
  • iodine  
  • iodoform  
  • iso-butane  
  • isocyanates  
  • isoprene  
  • isopropyl acetate  
  • isopropyl alcohol  
  • isopropyl ether  
  • keytones  
  • lactic acid  
  • mesityl oxide  
  • methanol  
  • methyl acetate  
  • methyl acrylate  
  • methyl alcohol  
  • methyl bromide  
  • methyl cellosolve  
  • methyl chloride  
  • methyl chloroform  
  • methyl cyclohexane  
  • methyl cyclohexanol  
  • methyl ether  
  • methyl formate  
  • methyl isocyanate  
  • methyl methacrylate  
  • methyl tert-butyl ether
  • methylal  
  • methylcyclohexanone
  • methylene chloride  
  • monochlorobenzene
  • naphthalene  
  • N-Nitrosamine  
  • nicotine  
  • nitro benzene  
  • nitroethane
  • nitrogen compounds
  • nitroglycerine  
  • nitromethane  
  • nitropropane  
  • nitrotoluene  
  • nonane  
  • octalene  
  • octane  
  • pentanol  
  • pentanone  
  • pentene  
  • perchlorethylene  
  • phenol  
  • phosgene  
  • Polyamides (nylon-6)  
  • Polyethylene (PE)  
  • Polyethylene terephthalate (PET)  
  • Polymethylmethacrylate (PMMA)  
  • Polypropylene (PP)  
  • Polystyrene (PS)  
  • Plasticisers  
  • propionaldehyde  
  • propyl acetate  
  • propyl alcohol  
  • propyl chloride
  • propylene  
  • pyridine  
  • rubber odour  
  • skatole  
  • styrene monomer  
  • sulphur trioxide  
  • tar fumes  
  • tetrachloroethane  
  • tetrachloroethylene  
  • tetrahydrofuran  
  • toluene  
  • Toluene di isocyanate
  • toluidine  
  • trichlorobenzene  
  • trichloroethane  
  • trichloroethylene  
  • trichlorofluoromethane  
  • triethylamine  
  • trimethylbenzene  
  • turpentine  
  • urea  
  • uric acid  
  • valeric acid
  • valericaldehyde  
  • vinyl acetate  
  • vinyl chloride  
  • volatile organic compounds  
 
 
For further information on specific compounds and validity of capture from actual process, or liquid phase processing, please contact your sales representative for further review, and consultation or email purex@purex.co.uk. This list is not comprehensive, and is subject to change without notice.
 
Ends--