Corrosion Dendrite Formation Print E-mail
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Written by Chris Hunt   
Friday, 03 May 2013 01:41

Corrosion and dendrites formed across the surface of a plastic connector body between two terminations (Figure 1). This was caused by excessive flux sprayed on the top surface of the board. The flux could have also penetrated up through the connector by capillary action between the pin and connector body.

No-clean materials must be exposed to the correct preheat to permit full evaporation of the carrier solvent and deactivation of the flux. If a conformal coating had been used in this application, the same problem could have occurred on other sections of the board. Coating cannot overcome poor production setup or control when potentially corrosive materials are still on the board. Figure 2 shows copper dendrites between two connector terminations. The copper has formed over the solder mask due to the high concentration of moisture on this area of the circuit. This demonstrates that solder mask does not always help!

These are typical defects shown in the National Physical Laboratory’s interactive assembly and soldering defects database. The database (http://defectsdatabase.npl.co.uk), available to all this publication’s readers, allows engineers to search and view countless defects and solutions, or to submit defects online. To complement the defect of the month, NPL features the “Defect Video of the Month,” presented online by Bob Willis. This describes over 20 different failure modes, many with video examples of the defect occurring in real time.

Chris Hunt is with the National Physical Laboratory Industry and Innovation division (npl.co.uk); This e-mail address is being protected from spambots. You need JavaScript enabled to view it . His column appears monthly.

Last Updated on Friday, 03 May 2013 13:14
 

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