Bulletin Jan 09 Conformal Coating Failure Mechanisms Orange Peel

     

 

Technical Bulletin Jan 09 Common failure mechanisms in conformal coating: Orange Peel In conformal coating, there are several mechanisms that cause failure of printed circuit boards (PCBs). In a series of technical bulletins SCH will examine the common failure mechanisms in conformal coating including capillary flow, delamination, cracking, loss of adhesion, dewetting, corrosion, orange peel, pin holes, bubbles and foam.

Conformal Coating Failure Mechanism: Orange Peel Definition An uneven textured surface, often appearing dull, which looks like the skin of the orange. Causes of Orange Peel in Conformal Coating Factors that can cause orange peel effect include: 1. The improper application of the conformal coating. This manifests in aerosol or spray gun application where the coating is applied too far away from the PCB and the coating is too “dry” on the surface to level out. 2. The incorrect thickness of the coating where not enough coating is deposited so that there is insufficient conformal coating to self level. 3. The incorrect cure profile when using an accelerated curing mechanism. This could be that the flash off zone before heat curing is inadequate or the oven profile is incorrect.   Examples of Conformal Coating orange peel effect.

  SCH Technologies is a Trading Name of SCH Services Limited  Newburgh Building, McLintock Way, Barnsley, South Yorkshire. S70 6BF    Tel: +44 (0)1226 297711 Fax: +44 (0)1226 297733  www.conformalcoating.co.uk 

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Ex xamples of o Orange e Peel Effect   Th he main issue with ora ange peel effect is th hat the con nformal co oating may y be too thin to o offer ade equate pro otection to the PCB.

Ho ow to stop p Orange Peel Effec cts in Conformal Coating 1. Redu uce the visc cosity of th he confo ormal coatting to allo ow the coatiing to leve el. 2. Redu uce the air pressure to o the spray y gun to t reduce the t evapo orate effec cts on the conform mal coating g. mise the disstance for spray 3. Optim application to the t manufa acturer speciification when apply ying the confo ormal coatting. 4. Ensure enough layers of coating c are e applied to form m a levelled d coating. This is especially y true for aerosols which h are susce eptible to this t issue. 5. Increase the fla ash off time e for the solvents to evap porate beffore ramp ping up the e temperatture for eleva ated curing g of the co onformal coatiing. 6. Re-prrofile the curing oven n using the confo ormal coatting materrial supplierrs recom mmended profile.

Exampless of Orange Pe eel courtesy off Humiseal Euro ope

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Conforma al coating SSubcontract Servicess

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Global sup pply of Conformal Co oating Applicatio on Equipme ent

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Humiseal Conformal C l Coatings

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Conforma al Coating Training co ourses

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Conforma al Coating Consultation & troublesho ooting PLEASE CH HECK OUR WEBSITE FO OR DETAILSS ww ww.conform malcoating g.co.uk

  Future Bu ulletins •

Co ommon Co onformal Coating C Fa ailure Mech hanisms co overing de--lamination n, loss of ad dhesion, de e-wetting, corrosion, orange pe eel, pin ho oles, bubble es and foa am.

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Co onformal coating c CTTI (Comparrative Tracking Index).

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Co onformal coating c inspection: in nspect con nformal coatings corrrectly using g the co orrect crite eria to imprrove long term t reliab bility.

SCH Tech hnologies is a TTrading Name o of SCH Services Limited  Newburggh Building, MccLintock Way, B Barnsley, South Yorkshire. S70 6BF    Tel: +44 (0)1226 29771 1 Fax: +44 (0)12 226 297733  www.con nformalcoatingg.co.uk 

SCH Technolo ogies are ISO9001 1 and ISO14001 certified