Konform® SR Silicone Conformal Coating

Measuring the thickness of conformal coating is essential to ensure proper application and adherence to the specified requirements. There are several methods used to measure the thickness, and the choice of method may depend on the type of conformal coating and the level of accuracy required. Here are some common methods:

• Calibrated Thickness Gauges: These are handheld devices that use non-destructive methods to measure the thickness of the coating. They typically use magnetic induction or eddy current principles to determine the distance between the probe and the substrate, which correlates to the coating thickness.
• Cross-Sectioning and Imaging: This method involves cutting a sample of the coated surface and examining it under a microscope. The thickness can be determined by measuring the height of the coating in the cross-sectional view.
• Ultrasonic Testing: Ultrasonic thickness gauges use sound waves to measure the thickness of the coating. The device emits ultrasonic pulses, and the time taken for the waves to bounce back from the substrate-coating interface is used to calculate the thickness.
• X-ray Fluorescence (XRF): XRF can be used to measure the thickness of conformal coatings. It involves analyzing the intensity of X-rays emitted from the coating material due to bombardment by X-rays. The thickness is determined based on the X-ray penetration depth.
• Electrical Capacitance Method: This method utilizes the change in capacitance between electrodes positioned on opposite sides of the coated surface. The coating's thickness affects the capacitance, allowing for indirect measurement.
• Weight Difference Method: For some applications, the thickness can be estimated by measuring the weight difference of a substrate before and after coating. This method is more suitable for thicker coatings.

Before choosing a specific method, it is important to consider factors like the type of coating material, the size and shape of the substrate, the required measurement accuracy, and whether destructive or non-destructive testing is acceptable for your specific application. Additionally, it is essential to calibrate the measurement equipment and follow any manufacturer's guidelines for accurate and reliable results.

IPC-CC-830 is an industry standard focused on conformal coatings for printed wiring assemblies, while MIL-I-46058 was a military specification for electrical insulating compounds used on printed circuit assemblies, which has since been replaced by more comprehensive standards like MIL-STD-883 or adopted industry standards like IPC-CC-830. 

Yes, all our coatings meet IPC-CC-830 standards. IPC-CC-830 defines the requirements for electrical insulating compounds, commonly known as conformal coatings, used to protect printed circuit boards and electronic assemblies from environmental factors such as moisture, dust, chemicals, and temperature extremes. The standard outlines the testing methods and performance criteria for these insulating compounds to meet industry requirements. It includes specifications for material properties, application procedures, and performance testing for conformal coatings. You might see IPC-CC-830B, 830C, etc. The extra letter refers to the revision. The changes between revisions general do not affect all types of coatings, so coatings are often not retested to the latest standard.

1. Prepare the PCB: Ensure the PCB is clean, dry, and free from any contaminants. Clean it using an appropriate PCB cleaning solution or isopropyl alcohol to remove any dirt, flux residues, or other impurities that could interfere with the coating adhesion.
2. Select the Conformal Coating: There are various types of conformal coatings available, such as acrylic (AR), silicone (SR), and urethane (UR). Choose a coating that suits your specific application and environmental conditions.
3. Choose the Application Method: Conformal coatings can be applied using different methods, including spraying, dipping, brushing, or dispensing. The method you choose depends on the type of coating and your equipment's capabilities.
4. Spraying: Suitable for large-scale production. It requires a specialized spray booth and spray gun to evenly apply the coating.
5. Dipping: Involves immersing the entire PCB into a reservoir of conformal coating. This method provides uniform coverage but may trap air bubbles.
6. Brushing: Manual application using a brush is suitable for small-scale production or touch-ups.
7. Masking Uncoated Areas (optional): If certain components or areas on the PCB should remain uncoated (e.g., connectors, switches, or heat sinks), use a masking material (e.g., Kapton tape or liquid latex) to protect those areas during the coating process.
8. Dispensing: Applying the coating using a controlled dispensing system, which is useful for selective coating on specific areas. Make sure to apply a thin and even layer, avoiding excessive buildup, which could lead to uneven coating thickness or encapsulation of sensitive components.
9. Curing and Drying: Allow the applied conformal coating to cure and dry as per the manufacturer's instructions. This typically involves leaving the coated PCB in a controlled environment, such as an oven, for the recommended duration.
10. Post-Coating Inspection: After the coating has cured, inspect the PCB to ensure proper coverage and to check for any defects, such as bubbles, pinholes, or insufficient coating.

While conformal coatings can offer some level of protection against ESD by providing a barrier between the sensitive electronic components and the surrounding environment, they are not specifically designed as ESD control measures.

Full cure is when it meets all the final specifications. There might be some out-gassing, but it will be as hard as it is going to be, and adhesion is as good as it gets.  Tack-free is as the name suggests, not sticky so you can move it along the assembly process.

Every organization using hazardous chemicals within their facility has the responsibility to equip their facility and personnel to maintain exposure levels below the TLV. Personal monitoring badges can be used to measure exposure of a specific material. Then, depending on the threshold limit and the application, exposure can be controlled with PPE like masks, face shields, respirators, and even coveralls. If they don’t reduce exposure below the recommended limit, you will need to consider a special ventilation hood or even containment booth. As you can see, as the exposure limit gets down to a certain level, the equipment required to safely use the solvent can get impractical. At that point, your best option is to consider a safer alternative.

The dielectric strength is material intrinsic property and withstand voltage is surface property which depend on thickness of the material. They can be slightly different for thicker materials, but for conformal coating, the two numbers should be very close or the same. That is because we test coating at 3-5 mils thickness, calculate, then report the value per mil.

Conformal coating with UV tracer can be inspected with any typical UV lamp which has wavelength of 320-380 nm.

Toluene or acetone can be used as a thinning agent. Make sure it is anhydrous, so contains as little moisture as possible.

Apply to clean, moisture-free surface.  Areas not requiring coating should be masked. Application: Coating may be applied by spraying, brushing, dipping or flow coating.  Allow coating to flow around components. Cure:  Room temperature cure: A 1.0 mil coating will be tack-free in 15 minutes.  Full cure requires 24 hours @ 77˚F (25˚C). Heat cure: 8 hours @ 170˚F (77˚C). An open vessel of water placed in the drying chamber will facilitate curing. UV detectable for QC inspection. Removal:  Coating may be removed by soaking in Electro-Wash® Two Step Cleaner Degreaser. Use CircuitWorks® Conformal Coating Remover Pen for spot removal. After the new component is installed, areas should be cleaned and recoated.

Shake well. SURFACE MUST BE CLEAN & MOISTURE FREE. Areas not requiring coating should be masked. Coating:  Spray top to bottom, allowing coating to flow around components. Rotate board 90˚ and repeat process 2 or more times.  If nozzle clogs, clean with solvent or use new nozzle. Cure:  A 1.0 mil coating will be tack-free in 15 minutes.  Full cure requires 24 hours @77˚F/25˚C. Heat Cure: 8 hours @170˚F/77˚C. An open vessel of water placed in the drying chamber will facilitate curing. UV detectable for QC inspection. An open vessel of water placed in the drying chamber will facilitate curing. UV detectable for QC inspection. Removal: Coating may be removed by soaking in Electro-Wash® Two Step. Use CircuitWorks® Conformal Coating Remover Pen for spot removal. After the new component is installed, areas should be cleaned and re-coated.

In almost all cases, the cloudy or milky cure comes from coating in higher humidity conditions. The white foam (from an aerosol) is caused the same way. We have the following suggestions:

1. If possible, allow the substrate and coating material to come to approximately the same temperature when applying.
2. Avoid applications in RH > 60%. High humidity ranges will discolor some coating resins and will start curing others. Besides the aesthetic value, it certainly may affect adhesion to the material.
3. Specifically on the silicone coating, if the resulting application is foamy, increase the focal point of the can, ie back off to about 10 -12” from the substrate & make 2 -3 light passes rather than one heavy pass to coat the board.

Wet film thickness = Sq. ft. per gal.

0.1 mil = 16,040

0.5 mil = 3,210

1 mil = 1,600

2 mil = 802

3 mil = 535

4 mil = 401

5 mil = 321

6 mil = 267

7 mil = 229

8 mil = 201

9 mil = 178

10 mil = 160

Metal 5-gallon containers come with a flexible pop-out spout for easy pouring. 55-gallon drums are compatible with standard 2" spouts.

It may be different state-by-state, so contact your state environmental agency for regional specific regulations. For a general guideline, here is the process according to EPA hazardous waste regulations 40CFR. The can has to be brought to or approach atmospheric pressure to render the can empty. Puncturing is not required, only that it “approach atmospheric pressure”, i.e. empty the can contents until it’s no longer pressurized. This insures that as much contents as is reasonably possible are out of the can. It is then considered “RCRA-empty”. At that point it can be handled as any other waste metal container, generally as scrap metal under the recycling rules. Note that the can is still considered a solid waste at this point (not necessarily hazardous waste).

The shelf life of a product can be found on either the technical data sheet (TDS), available on the product page, or by looking on the certificate on conformance (COC). The COC can be downloaded by going to https://www.chemtronics.com/coc. Once you have the shelf life, you will need to add it to the manufacture date for a use-by date. The manufacture date can be identified by the batch number. The batch code used on most of our products are manufacture dates in the Julian Date format. The format is YYDDD, where YY = year, DDD = day. For example, 19200 translates to the 200th day of 2019, or July 19, 2019. This webpage explains and provides charts to help interpret our batch numbers: https://www.chemtronics.com/batch-codes.

I suggest you get into the habit of clearing the valve after every use. You turn the can upside-down and spray until it only sprays propellant. If you don’t do that, you run the risk of dried coating building up in the valve or actuator button. If in the button, you can switch it for another one and it should work. If in the valve, there may not be much you can do to save the can.