Guyson International has recently installed a specialised version of its Formula 1400 blast cabinet into an aerospace & defence manufacturer, for the selective removal of conformal coating from printed circuit boards (PCBs).

If during testing or usage a circuit board develops or registers a fault then instead of scrapping the entire board, which could incur very considerable costs, selective conformal coating removal is undertaken so that the damaged components can be replaced or reworking such as re-soldering can be undertaken.

This specialist Formula ESD version is based on the well-proven Guyson Formula 1400 blast cabinet which has been specifically adapted for this application and comes complete with a Guyson 21 twin bag dust collector. Blasting is undertaken with the standalone 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 that propels the blast media, from the single blast pot, to selectively remove the conformal coating. Choice of blast media depends on the type of conformal coating and options include Walnut Shells, Sodium Bicarbonate, Plastic and Wheat Starch.

All blasting operations generate some level of static electricity and if this potential is not conducted away an electrostatic discharge (spark) can occur. Hence this Guyson Formula ESD version comes well equipped with preventative measures to enable safe blasting.

ESD specific features on the cabinet include an ionising air curtain, fixed to the inside back wall of the cabinet, this provides a high-speed laminar sheet of ionised air which 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 attached 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.

This specific Formula ESD version of blast cabinet is supplied with ultra-violet lighting. This is because some conformal coatings that are UV cured give an enhanced fluorescent response which makes the coating more visible under these ‘black lights’, so aiding operator accuracy when blasting.

www.guyson.co.uk