Printed Wiring Board Masking Tapes, Masking Coatings and Masking Gels

High-Reliability Cleaning and Conformal Coating Conference

– November 18-20, 2014
Schaumburg, Illinois | Chicago Marriott Schaumburg

 CRITICAL PROPERTIES OF MASKING TAPES AND MATERIALS IN PROTECTING ELECTRICAL CONTACTS, GOLD FINGERS AND PINS IN the CONFORMAL COATING PROCESS:

  1. Contains no silicone
  2. Anti-static
  3. Non-porous and pin-hole free to prevent contamination of conformal coating in circuit areas that should remain clear
  4. Easy to apply or short air drying or curing cycle
  5. Good adhesion to the circuit board while conformal coatings are being applied
  6. Easy to remove when the conformal coating process is complete
  7. Clean and leaves none or minimal residue that will effect the function of the PWB
  8. Withstands high temperatures and long curing cycles
  9. High material integrity comes off in one piece without tearing or flaking
  10. Ideally does not require the use of solvent or water for cleaning

Smartphones and mobile communication devices for active users that enjoy outdoor activities will benefit from effective conformal coating. Whether a high volume factory install or a do-it-yourself project,  environmental protection without use of toxic solvents is available using AIT’s easy to use conformal coating protection in the form of a masking tape or gel.

Condensation of water onto circuit board not properly protected with suitable conformal coating can cause pre-mature failure by galvanic and other acid and toxic elements such as Hydrogen Sulfide and sulfur dioxide laden moisture. AIT PRIMA-COAT CC7090-E and CC7130-E are the only proven moisture blocking conformal coating that can be applied in the field or in the lab.

Advanced computing electronics when used in outdoor and harsh environment will benefit from the unique moisture and water blocking of PRIMA-COAT conformal coating. The coating can be easily applied at home do-it-youself (DIY) by following simple instruction of masking the interface contacts with any household tape. Even mistake is made, the excessive conformal coating can be removed mechanically or with the suggested solvent.

The only real thing to avoid is in applying AIT PRIMA-COAT conformal coatings is masking the electrical interface contacts shown above. If mistake is made, simply removed with the suggested solvent or mechanical means (avoid removal of contact preservation layer such as gold plating).

Battery onboard of circuit board are major cause of concern in corrosion and other failures. Unlike most of the traditional conformal coating, AIT PRIMA-COAT CC7090-E and CC7130-E may be applied directly onto the connected battery terminals to protect the contact from corrosion. The molecular flexibility of the AIT conformal coatings are one of a kind that allow the removal of battery easily for replacement. Additional coating may be applied after the battery is replaced for another round of protection.

Conformal coatings for specialized applications that were not originally designed by the OEM, AIT PRIMA-PROTECT CC7130-E and CC7090-E may be brush coating in the field. Unlike most traditional conformal coating, the thickness is not critical. It can be as thick as 5-10 mils or 125-250 micron or even thicker and will not induces stress on any part of the board and component to cause stress-induced failure. Besides the unparalleled moisture blocking performance, the ease of use is another important design in the AIT conformal coatings.

For dip coating process or spray coating process in applying conformal coating, masking for electrical contacts are important for most traditional conformal coating. AIT PRIMA-PROTECT CC7090-E and CC7130-E may be removed relatively easily mechanically or with suggested solvent if mistakes are made.

Anti-Static Masking Tape and Film Form Dispensing Masking Coating and Masking Gel for Masking and Protection in Conformal Coating Processes

A complex PWB and PCB that requires conformal coating protection against water, condensation humidity, and other damaging environmental exposure also requires a cost effective masking solution for high volume application and removal. AIT provides some of the most innovative masking solutions from conformal masking tapes to film forming gels and coatings.

AIT’s  MT-100-S flexible masking tape conforms to complex areas that have components and pins that are difficult to cover with traditional PET or Polyimide masking tapes.  AIT’s ML-150-S and MG-150-S are masking film forming liquid coatings and easily dispensed gels that can be used to cover both large and small areas with different contours respectively.

Before conformal coatings are applied, the areas and parts that cannot be covered by conformal coatings such as connectors, gold finger contacts, etc. must be masked. There basically are two types of masks that are commonly used:

  1. Masking tapes based on polyimide or polyester carrier films that are coated with pressure sensitive adhesives. One of the bigger drawbacks is that they are mostly unable to provide anti-static protection.
  2. In some special applications, a special “curable” latex liquid can be applied onto specified areas to form a film that can be peeled off when conformal coating is finished. These latexes need to be cured with moisture and heat and thus additional processes are required.
  3. In some cases, special “boots” that are custom designed to specific connectors are made to perform “masking” applications. This approach can be effective for some large volume production scenarios but may be costly for others.

AI Technology, Inc. offers several improved and innovative masking material solutions for protecting those contact areas that need to be masked.

  1. MT-100-S is an AIT conformable masking tape based on a proprietary high temperature flexible carrier film that is much more conformable than the more rigid PET or Polyimide carrier films. More importantly, AIT’s conformable masking tape and rubbery film is embedded with inherent anti-static properties along with a controlled release pressure sensitive adhesive for masking. AIT conformal masking tapes can be used at temperatures as high as 250°C, a rate comparable to that of the polyimide-based masking tapes.
  2. MG-150-S is another AIT innovative masking film forming solution that is based on a gel-like dispensable paste that can be applied onto pins and high contour circuit areas to be protected. These dispensed gels are designed for small areas and are then air dried to form masks that can be peeled off easily when conformable coatings are cured.
  3. ML-150-S is a variation of MG-150-S that can be coated with brush or applied using a syringe to a small confined area to form a masking film. The ML-150-S is a masking film forming coating that is applied onto larger circuit areas and can air dry within 10 minutes to form a masking film. It is advisable to have a slightly thicker coating in at least one edge so they can be readily grasped for easier removal after conformal coating.
    • It is always advisable that the masking materials (tapes, gel-form-masks, liquid-film-masks) be removed after the conformal coating application and before the conformal coating is “cured.”
    • Removal of masking materials will facilitate clean removal without tearing off some of the conformal coating or weakening the conformal coating edge sealing capability.

AIT’s CC7090-E and CC7130-E even at ultra-thin conformal coating thickness of less than 25 microns provides unparalleled protection for Smartphones and mobile electronics. AIT’s ML150-S masking film forming gel is ideal for electronics less than 25 micron thick with miniature connectors and pins.

Masking Tapes for Conformal Coatings & their Relative Merits
Masking Tapes MT-100-S

Conformal Masking Tape that adapts to non-flat contacts and capable to “band-aid” cover the connectors

ML-150-S: Masking Film Forming Liquid

MG-150-S: Masking Film Forming Gel (Thicker thixotropic Paste)

Traditional Masking Tape with Polyester (PET) or Polyimide Carrier
Application Method Cut to right side and apply pressure to tape on areas to be protected Dispense onto areas that need protection.

High viscosity paste to allow thick film forming for easier peel off

Cut to right side and apply pressure to tape on areas to be protected
Conformability Excellent

Flexible proprietary conformal carrier film (non-silicone)

Excellent. Ideal for use on pins and contoured areas

Air dry @ <60 min to flexible mask film (Toluene Free solvent )

Good to moderate

The relative stiffness of the PET or Polyimide carrier

Anti-Static Protection Outstanding on both pressure sensitive layer

Embedded in the flexible carrier film

Outstanding and embedded in the air dry film formed from the brush or paint on liquid Depends

Typically no

Ease of peel and removal Controlled peel

Zero to minimal residual

Controlled peel

Zero residual

Depends

Vendor specific

Water Immersion Resistance Inert and hydrophobic Inert and hydrophobic ?
Temperature Exposure Stability Up to 250°C for 60 min. Up to 200°C for 60 min. Good
Chemical Resistance Inert to acid and base

Inert to spraying solvents

Inert to acid and base

Inert to spraying solvents

Good
Cost of Application Moderate Low Expensive

AIT application engineering, sales, chemists, and material scientists are ready to serve your special needs and applications. Please inform us of your requirements using the Contact tab or click on the button below:

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AIT technical sales and service department can also be reached at: 1-609-799-9388 or 1-800-735-5040 (EST) and Fax: 609-799-9308