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James Carr-Pries

James Carr-Pries

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Background

In the past, we have had issues with debris on our boards causing inaccurate measurements, particularly on the AFEs. This caused battery faults when in fact the battery was completely fine. We want to avoid these false positives to increase the reliability of the car. During regular car operation, filtering out these particles would mean decreasing the airflow through the electrical enclosures, thus diminishing our cooling ability - this may be fine. However, the electrical enclosures are open very often for debugging/replacing/upgrading boards, so we would like the protection to be part of the board itself.

We are not necessarily expecting liquid to spill on the boards, but it can (and has - FSGP 2019, and I’m sure earlier as well) happen , since we do clean our solar array by spraying water on it and potentially have to drive in the rain during competition.

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Type

Description

Advantages

Disadvantages

Price / Purchase links

Silicone Resin (SR)

Confromational Coating using a Silicon Resin Base

  • Higher working temperature (-40C to 200C) 

  • High chemical and general resistance protection

  • Challenging removal (need special solvents, long soaking periods and even brushes)

  • Expensive

$37CAD - https://uk.farnell.com/electrolube/fsc400/coating-silicone-flexible/dp/1616570 ($37)

Acrylic Resin (AR)

Confromational Coating using a Silicon Resin Base

  • Most Affordable

  • High Dielectric Strength 

  • Very easy to remove (using a variety of solvents)

    • Good for reworking and debugging

  • Simple drying process (<20 minutes)

  • Working temperature range: -40C to 60C (short term protection to 100C)

  • Not the best in class at protection but still sufficient

$17CAD - https://ukwww.farnellmouser.comca/ambersilProductDetail/6130004030MG-Chemicals/acrylic-con-coating-400ml/dp/1666251?st=Conformal%20Coating%20Aresole$16CAD - 844AR-340G?qs=T3oQrply3y9urZcHv3hIkA%3D%3D

$28 but free shipping to Canada https://ukwww.farnellamazon.com/electrolube/apl400h/coating-conformal-acrylic/dp/3026838?st=Conformal%20Coatingca/MG-Chemicals-Acrylic-Lacquer-Conformal/dp/B008OA7178/

Potting Materials

Potting uses a "pot" in the form of a case, shell or similar enclosure, to completely cover the board, protecting it from the surrounding environment - a tough form-fitted shell around the board.

  • potting cases are secure

  • offer dielectric protection

  • safeguard the PCB from the polluting effects of acids, bases, corrosion, salt and most solvents

  • Very challenging to remove for reworking/debugging

  • No ventilation

Due to these downsides of potting, it would not be feasible for our purposes.


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  1. https://www.walmart.ca/en/ip/equate-beauty-100-acetone-nail-polish-remover-pump/6000200715614

    1. Nail polish remover with acetone can be used to remove areas of the coating that need reworking or to uncover leads

  2. Just apply the Nail Polish Remover

Todo

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Does it actually work? - look for reviews, actual tests

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Customer Research

r/solarracing

  • Other teams have resorted to just applying a silicon coating after all the debugging is done or using a full 3d printed enclosure. I would hesitate to take these routes because of my understanding of our project constraints. We are heavily dependant on passive air cooling so fully enclosing the board may not be feasible. Also, from what I understand we had the dust issues before the competition and need a solution during the testing phases too.

IPC Standards

  • IPC-CC-830C: This is the main standard for conformal coating. It is used to qualify different conformal coating products, and contains sections on materials, shelf life, curing, chemical, viscosity, and appearance requirements. It also contains standards on fungus, moisture, and flammability resistance as well as dielectric withstanding voltage and other electrical specifications.

  • IPC-A-610G: This standard covers the acceptability of electronics assemblies, and as such has a section on the requirements for conformal coating coverage and thickness.

  • IPC J-STD-001F: This standard covers the requirements for soldered electrical and electronic assemblies, and has a section dealing with materials and application of conformal coatings

General Overview of PCB Protection Methods: https://www.tempoautomation.com/blog/what-are-the-best-pcb-moisture-protection-methods/

IPC Standards for Conformational Coatings: https://resources.pcb.cadence.com/blog/2020-understanding-ipc-conformal-coating-standards

Choosing the coatings best for us: https://www.techspray.com/the-essential-guide-to-conformal-coating

https://www.electroniccoating.com/resources/conformal-coating-comparison-guide/

General Information about various types of coatings: https://electrolube.com/knowledge_base/what-are-conformal-coatings/

https://www.techspray.com/conformal-coating

Tech Sheet for Acrylic Resin (first link): https://www.mouser.ca/datasheet/2/265/tds-844ar-a-1600563.pdf

Todo

  1. Continue Discussion with other Solar Car Teams on reddit