Types of Conformal Coatings, Applications and Process Issue MitigationAuthors: David Allen, EMBA, BSEET
Company: Libra Industries
Date Published: 10/14/2012 Conference: SMTA International
Issues that may be encountered and potential causes IPC standards indicate the acceptance criteria for conformal coating and provide examples of what qualifies as a defect, but there are few sources that provide ways to prevent or eliminated said defects. The primary intent of this document is to introduce the methods, processes and procedures to mitigate the defects outlined in the IPC documentation. These methods will be discussed in the section of this document titled: Methods of issue mitigation.
During the installation of a dual line conformal coating room comprised of a UV cured urethane and a VOC based Acrylic, it was necessary to keep many factors in mind. There are many suggestions and methodologies in the market that may be fact or conjecture, this document describes methodologies born from trial and error.
Although many of the defects outlined in IPC-610E are eliminated by thoroughly cleaning the board prior to coating, the greatest challenges have been overcoming issues with capillary action and bubbles.
The capillary action dilemma was solved by using a relatively new coating process. This process also significantly reduces and in many cases completely eliminates the need for standard tape and boot masking procedures and in turn considerably reduces the number of labor hours spent on this process. The mitigation of the capillary action dilemma will be discussed later.
Bubbles are the greatest concern especially with an automated process. Bubbles can be laid down by the machine, they may be in the pot or they may be generated when the material is filtered. Bubbles can be trapped on the board while trying to exhaust from under components or they can be generated by material interaction. Each of these topics will be discussed later with solutions for mitigation.
conformal coating, process control, managing IPC defects
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