It is possible to remove unwanted conformal coatings from PCBs in-shop. The process can often be accomplished by either the assembly’s original equipment manufacturer (OEM) or an end-user, but the capacity to do so doesn’t always exist. For these parties, conditions affecting the poor coating may:
- be beyond the purview of their experience with conformal materials or
- exceed the capacities of their available removal equipment/supplies.
In addition to poor coating finishes, the need for removing conformal films can arise any time following PCB completion. There can be many causes; an extreme variety of process/product requirements or component replacement issues can significantly diminish a coating’s functional integrity. When these circumstances develop, or if the process is just too complicated/inconvenient to complete, it is advisable to seek the assistance of professional conformal coating removal services.
Coating Conditions Leading to Removal
When the coating is beyond repair, removal may be the only way to save the assembly. Conditions that can lead to coating removal include:
- Contaminants: Contaminated substrate surfaces interfere with coating adhesion. If left untreated too long, removal may become necessary.
- Delamination: Separation of the conformal coating from the substrate produces a finish characterized by torn, unattached, and non-conformal coating, defeating the film’s purpose.
- Masking/prep: Poorly implemented masking of component surfaces not targeted for coating disrupts their ability to function as designed.
- Outgassing: Gaseous emissions from a processed layer of coating film generates poor coating performance, potentially leading to the need for coating removal.
- Solder joint defects: Depending on their properties and application processes, conformal coatings can increase assembly solder joint fatigue, if the coating material is not suitable to the PCB’s purposes or is improperly applied to the assembly.
- Tin whiskers: Spikey, whisker-like protrusions along the surfaces of metal components, these are responsible for PCB arcing and short-circuits. Eliminating their presence can require coating removal.
- Vessication: Blister formation between semi-permeable film coatings and another surface material can become severe, rendering the original conformal film dysfunctional.
Skill and Conformance Requirements
Successful removal of conformal films largely depends on the levels of operator skill and experience. Advanced operator skill levels, at the upper echelons of technician proficiency, are necessary for many removal functions. As important is the ability to accurately identify the coating material, mandatory for successful removal. This is simple enough if recoating is being done by the original manufacturer, since the specific coating used is known as a matter of company record.
However, this is not always the case, compelling appropriate material identification prior to commencing removal processes. Stripping materials can also be hazardous. Caustic removal materials demand application of highly specialized aptitudes and technical procedures, frequently beyond the means of OEM personnel or end users.
Skilled professionals are better equipped to properly test the film for reliable identification of coating characteristics, to more precisely determine appropriate removal procedures. Hence, they can closely duplicate the physical characteristics of the original, within the constraints of such conformance issues as the assembly’s environmental, functional, and serviceability requirements.
Diamond MT’s considerable experience removing conformal coating from PCBs minimizes the risks involved to board assemblies, whether localized or complete removal is needed. Successful removal is cost effective, minimizing downtime. Diamond MT offers a highly skilled workforce and rapid turnaround on coating-removal assignments, also providing highly reliable recoat, according to your precise specifications. Our established quality program, combines with knowledge of commercial manufacturing requirements, competitive pricing and on-time delivery, to offer clients superior conformal coating removal services, followed by recoat, if requested.
To discover more about conformal coating rework and removal, download our whitepaper now: