If during testing or usage your circuit board develops or registers a fault, then instead of scrapping the entire board, which could incur very considerable costs, choose selective conformal coating removal. This can be performed so that the damaged components can be replaced or reworking, such as re-soldering, can be undertaken. Guyson recommends using the Guyson Formula CCR microblast cabinet for this application.

The method of conformal coating removal is determined by the type of coating resin and size of the area to be removed and the various methods of removal include solvent, thermal, peeling, scraping and micro blasting. Each has its own suitability and weaknesses, though micro-blasting is maybe the least problematic of the removal methods and also the most predictable. Some of the other methods also involve risks to the boards and personnel by using sharp knives and handheld grinders, hot soldering irons and toxic fumes during coating removal.

The most common types of conformal coating include Acrylic, Silicone, Polyurethane, Epoxy and Parylene; the last two are often the methods of choice for high-end PCB usage where there is a critical need for high resistance to abrasion, solvents, moisture and temperature; so these are frequently chosen in stringent military usage. These coatings are usually applied very thin - in the region of 25 to 125 microns - providing the maximum amount of protection for the minimum amount of coating. Both Epoxy, and especially Parylene - due to its hardness - are highly suited to micro blasting removal and are difficult for several of the other methods of removal.

For the safe and selective removal of these types of conformal coatings, Guyson recommends the specialist Formula 1400 CCR blast cabinet version which has been specially developed for this application and comes equipped with a range of Electro Static Discharge (ESD) reduction features.

The Formula CCR version is based on the well-proven Formula 1400 blast cabinet which comes complete with a Guyson 41 dust collector. Blasting is provided by the stand-alone pressure-fed Pencil Blast unit which is fitted onto an external shelf on the left-hand side of the cabinet. This unit is provided with a micro nozzle (available with 0.8 mm, 1.2 mm or 1.8 mm blast nozzle bore) that propels the blast media, from the single blast pot, to selectively remove the conformal coating. The choice of blast media depends on the type of conformal coating and options include Walnut Shells, Sodium Bicarbonate, Plastic and Wheat Starch.

ESD reduction features on the Formula 1400 CCR cabinet include an ionising air curtain, fitted to the inside back wall of the cabinet, this provides a high-speed laminar sheet of ionised air that washes down over the components and floods the chamber with ionised air for static neutralisation. An ergonomically designed handheld air-assisted ionising gun, for localised use, neutralises static charges and removes dust contamination on the individual boards. Additionally, extensive earth-grounding straps are fitted to all individual items of the entire blast system and finally, an earth grounding spike is used to protect each item to be blast abraded.

A handheld Ultra-Violet inspection torch is provided as some conformal coatings, that are UV cured, give an enhanced fluorescent response which makes the coating more visible under these ‘black lights'.

If you would like to improve the safety and quality of your conformal coating removal, please contact Guyson’s Customer Service Department now to arrange free blast trials on your components, prove the process and make recommendations on the most suitable cabinet for you – call 01756 799911 or email info@guyson.co.uk