Parylene Coating Blog by Diamond-MT

Conformal Coating Boots vs Tape:  Making the Right Choice

Posted by Sean Horn on Fri, Jan 27, 2017 @ 07:24 AM

Masking tapes and boots both protect components for a selected range of masking functions.  Choosing between the two is crucial to achieving optimal masking protection.  Conductivity needs to be maintained in all cases.  In addition, such operational factors as the:

  • assembly’s production volume,
  • surface geometry of the component/assembly, and
  • type of coating applied to the assembly substrate
  • influence whether tape or boot masking material is the best choice.

Masking TapesIMAG1334reducedsize.jpeg

Masking tapes, and smaller dots, represent a highly accepted and standardized method of masking, successfully used from the outset of conformal coating processing.  Since their hand-application is labor intensive and time consuming, they are mostly used for masking low volumes of assembly components.  Tapes are also very efficient protecting such flat assembly areas as the edges of PCBs or conductive pads.  Their counterpart, masking dots, are optimally used to safeguard smaller, specified keep-out sites like mounting holes.  Tapes and dots are available in different colors, sizes, levels of adhesion and material type, expanding their range of application.   As with all masking, the key is to choose the right tape or dot for the assembly and its coating process

There are, however, some problems masking conformal coating with adhesive tapes; these issues include:

  • Adverse reactions between the tape and conformal coating can generate de-wetting effects on the PCB. Assuring compatibility with such conformal film materials as solvent-based acrylic, silicone and polyurethane safeguards the tape from responding unfavorably to the solvents.
  • Conformal coating can seep under the tape because of bleeding/leaking during film application, if masking is poorly implemented. Consequent failure to stop the coating penetration into keep-out areas may necessitate such costly, time-consuming repairs as fixing the leak, removing the conformal coating from the assembly, replacing the improperly masked component, or scrapping the entire assembly.
  • Difficult removal during de-masking can leave adhesive residues that require additional labor (cost/time) to be removed, potentially leading to longer-term performance issues.
  • Unwrapping occurs when the mask does not remain sealed during processing, so the tape cannot adequately protect the assembly from intrusion by the coating.

Masking Boots

In comparison, recyclable masking boots provide a cost-effective and labor-saving option to taping processes.  They are far more efficient for large-batch component masking, and can be custom-made to accommodate an exceptional range of component alternatives.  In this respect, boots are advantageous for assignments requiring repeat masking of high volume production, effectively covering entire components in some cases.  After the initial expense, boots’ RoI easily surpasses hand-masked tapes.  

Unlike tapes, masking boots generate dependable defense for a wide range of assembly components for ALL conformal coating types and application techniques.  Included processes are:

  • batch/selective robotic spraying of PCBs and related assemblies,
  • dipping processes, either horizontal or vertical, and
  • parylene CVD.

To add to their versatility, boots can be custom-made to clients’ precise assembly/component specifications.  Utilization is simple, with boots being fastened over the selected components (connectors, plugs, sockets, etc.) needing protection from conformal coating application. 

Correctly choosing between masking tapes and boots is critical to implementing efficient conformal coating procedures.  Failure to do so often leaves electrical components exposed to conformal coating, a development that can lead to component dysfunction.  In general, tapes are most effective for flatter surfaces and smaller production runs.  Reusable masking boots are a more efficient and cost-effective option for masking larger production volumes, better adapted to a wide range of component shapes and sizes.

To learn more about conformal coating masking boots and other methods, download our whitepaper:

Conformal Coating Masking Whitepaper

Tags: conformal coating, conformal coatings, conformal coating masking, masking boots