The selection of conformal coating三*漆 material is a crucial factor that needs to be considered carefully and in relation to the application method.The wrong selection can not only affect the long term reliability of the circuit board but can cause m*ive difficulties with both processing and costs.

The most common standards for conformal coating三*漆 are * A-610 and *-CC-830. These standards list indications of good and bad coverage and describe various failure mechani*s such as dewetting and orange peel.

Conformal coating 三*漆inspection is a critical factor in determining successful coating application and long term reliability of PCBs. Using the * standards allows the coating operator to monitor the coating application performance. This can be done manually by the operator in an inspection booth by examining the PCB under white and UVA light or it can be done automatically by a conformal coating inspection system.

Another t*e of coating called Globond三*漆 is applied with a vacuum deposition process versus a spray or needle application. The Globond三*漆 is applied at the molecular level by a vacuum deposition process at ambient temperature. Film  conformal coatings from 0.100 to 76 μm can be easily applied in a single operation. The advantage of Globond三*漆  coatings is that they cover hidden surfaces and other areas where spray and needle application are not possible. Coating thickness is very uniform, even on irregular surfaces. The three main disadvantages are that  any desired contact points such as battery contacts or connectors must be carefully covered with an air-tight mask to prevent the parylene from coating the contacts,  it is a batch process and does not lend itself to high volume processing, and  the cost per PCB can be highly prohibitive due to the capital investment costs and the cost per batch.

There are many chemistries of conformal coatings三*漆 out on the market today. While the "Material Considerations" section below is very important to finding the correct conformal coatings三*漆, it is also important to find a coating chemistry which meets your application needs. Below are five common strengths for each conformal coatings三*漆 chemistry. Click here for a full list of pros and cons on the different conformal coatings三*漆chemistries

Acrylic

• Ease of rework
• Simple drying process
• Good moisture resistance
• High Fluorescence level
• Ease of viscosity adjustment

Epoxy

• Useful to about PA-5731
• Harder durometer, abrasion resistance
• *E closer to epoxy PCB substrate
• Higher Tg (Gl* transition)
• Good dielectric properties

Polyurethane

• Good dielectric properties
• Good moisture resistance
• Solvent resistance
• Less reversion potential
• Abrasion resistance

Silicones

• Stable over wide temperature range (in general, -40C to 200C)
• Flexible, provides dampening and impact protection
• Good moisture resistance
• High dielectric strength
• Low surface energy for better wetting

Fluorinated or non Fluorinated - Globond

• Excellent uniformity regardless of part geometry
• Chemical inertness
• Minimal added m* and low outg*ing
• Low environmental impact process
• Low dielectric constant

Amorphous Fluoropolymer

• Low dielectric constant
• High gl* transition temperature
• Low surface energy
• Low water absorption
• Solvent resistance

The basics of conformal coating三*漆 processing can be understood from a presentation available giving a summary of the areas covered above.

 

Links to online translation:The present article reprinted from DONGGUA*AOHANINUSTRIAL TECH*LOGY CO.,LTD
                                                 https://www.baohan-technology.com
                                                 https://www.globond.us