Conformal Coating Enhances Flexible Printed Circuit Board
The flexible printed circuit board is a key component of many electronics devices that integrate it into their functionality. In applications like aerospace and defense, consumer and automotive electronics, and telecom and appliance manufacturing, the PCB must be able to handle harsh environmental conditions. Conformal coating enhances the performance of these electronics, increasing reliability and lifespan.
Conformal coating protects the copper traces and other components of a PCB from harsh environments, preventing corrosion and oxidation. It also reduces the temperature at which the circuit will melt, and protects the substrate from moisture. This enables the circuit to withstand higher operating temperatures and allows it to work in harsher climates.
Conformal coats can be made of a wide variety of materials, and the choice is usually dependent on the specific application. It is important to balance the protective characteristics of each material with practicalities such as cost, application method, and suitability for the specific manufacturing process.
Some coatings are very easy to remove using solvents, while others require a more complex and time-consuming process. The removal method must also ensure that the solvents do not damage the PCB or its components. Depending on the material, conformal coating can be applied either by manual spraying or automated dispensing. The former uses a handheld spray gun to apply the coating, and requires that all areas not requiring the coating be masked. It is typically a less costly option but can lead to inconsistent coating across the board, especially if the operator is not skilled. The latter uses programmable robotic spray nozzles to accurately apply the coating, which can be more efficient and produce consistent results at higher production volumes.
How Conformal Coating Enhances Flexible Printed Circuit Board
It is important to use conformal coatings that are UL94 V-0 certified, as this ensures that they are non-flammable and self-extinguishing. It is also necessary to perform a series of dielectric breakdown tests on the coating before a manufacturer can use it. These tests are carried out by a specialist in the field, and provide the manufacturer with the necessary documentation for their products to comply with UL safety standards.
The final step in ensuring that the conformal coating is of a high quality is inspection. Traditionally, this has been done manually, with an inspector examining each PCB under a high-intensity, long-wave UV light to check for compliance. More recently, AOI systems have been developed, which can be camera or scanner-based. These allow for rapid and accurate measurement of the thickness of the coating, with results displayed in micrometer units.
A reputable conformal coating supplier should have the appropriate inspection equipment available to its customers. This should include a UV system for measuring the thickness of the coating, as well as other testing equipment.
For example, a conformal coating thickness gauge is used to measure the dry film on the circuit board. This is a non-destructive procedure that provides instantaneous results, but it is important to ensure that the probe is in contact with metal at each test point. Any gaps between the metal and the conformal coating will result in inaccurate readings.