Jidenco Powder Coating - Pulverbeschichten von Jidenco
Although there are alternative means of encapsulating electronic components, the Jidenco fluidised bed coating process offers one of the most efficient and simple ways of applying a coating with excellent electrical, protective and decorative characteristics, to electronic components. Employing powdered resins, the Jidenco system provides substantial advantages when compared to other methods in terms of lower material wastage, better coating quality, less fire/health hazard, and minimal capital, tooling or running costs.
Basic process description
The components to be coated are heated and dipped into a fine resin powder in a fluidised bed. Subsequent re-heating and immersing operations are carried out until the desired coating thickness is achieved.
In order to develop the full mechanical properties of epoxy resin coatings, post curing of the components in a batch oven, for a certain time and at a suitable temperature according to the powder employed, is needed.
Requirements of production coating equipment
Production equipment must comprise of:-
i) Component holding apparatus.
ii) A specialised fluidised bed containing the powdered resin. For many component types the powder must be fully fluidised in order that the components may enter it without resistance, and to allow a free flow of the powder around each component.
For certain components of particularly slim cross section, scraped mode is more suitable. This process allows the fluidising air having once been applied can be cut off prior to immersion of the components and the powder surface scraped absolutely level by mechanical means.
iii) A heating system.
Radiant heaters have proved the most simple and effective method of bringing components to the desired temperature. Control is achieved by timing the heating period very precisely according to the physical size and type of component.
iv) Powder replenishment and level control facilities. Radial lead electronic components have to be dipped into the fluidised powder to a consistently accurate depth in order to ensure complete coverage of the "body" with a minimum length of "trouser leg" i.e. the short length of coating on the lead wires. Therefore for applications needing a fully fluidised bed, the fluidised powder surface must be flat and free from eruptions.
For applications requiring the so called "scraped bed" (as mentioned in (ii) above), the powder surface must be mechanically scraped to complete flatness. Also as powder is taken from the bed by the coating components it must be replenished accurately to maintain the correct level.
v) Vibrators. To ensure a completely flat powder surface a vibrator must be incorporated into the base of the powder bed. Also, where it is necessary to remove excess powder from components a vibrator must be applied to the component bar (parts vibration).
vi) Transfer apparatus to convey the components between heater unit and fluidised bed.
vii) Process control instruments allowing the following variable functions to be pre-set to a suitable programme according to the component features and requirements:-
a) Pre-heat time
b) Dip time
c) Re-heat time
d) Dip count
e) Post-heat time