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With the rise in consumer electronics, screen interfaces, and electric vehicles over the past decade, printed circuit boards (PCBs) have established a vast foothold in everyday life. Accordingly, conformal coating formulations and their applications have increased since PCBs require protection from daily exposure to dust, humidity, moisture, salts, and other potentially damaging conditions. |
Several resin types are used in conformal coatings, including acrylic, silicone, epoxy, and polyurethane. Today, acrylic conformal coatings predominate the market due to their high dielectric strength, ease of removal for reworking, fast drying times, and excellent protection from moisture, humidity, fungus, and chemicals. Since resins directly influence and control many performance aspects in conformal coatings, it is important to select the right acrylic resin to ensure maximum performance of acrylic conformal coatings to protect PCBs.
Elvacite® Acrylic Resins for Conformal Coatings
For decades, Mitsubishi Chemical Group has produced
Elvacite® acrylic resins that serve as the backbone of many solvent-based coatings that protect various metal and plastic substrates for industrial applications. These resins are available in several grades as polymers or copolymers of methyl methacrylate and provide options in solubility range, film hardness and flexibility, and solution viscosity. Thus, formulators using Elvacite® can customize conformal coatings in several ways: selecting for specific coating-reworking solvents based on resin solubility profiles, creating conformal coatings for rigid or flexible PCBs, or ensuring the coating has the appropriate viscosity for the application method.
While several Elvacite® resins are suitable options for conformal coatings, all exhibit qualities that make them ideal. In particular, they perform the following:
- Create strong, abrasion-resistant films with excellent clarity
- Provide superior resistance to water, chemical fumes, and dilute acids and alkali
- Exhibit high resistance to dielectric burning and arching
Here are a few recommended grades for conformal coatings:
Elvacite® 2046
Elvacite® 2046 is a high molecular weight iso-butyl/n-butyl methacrylate copolymer resin that creates coatings with a good balance of abrasion resistance and strength while maintaining a high degree of flexibility due to its relatively low Tg. It facilitates excellent adhesion to varying nonporous surfaces and is soluble in a wide variety of solvents, including organic alcohol, ester, and ether solvents. Therefore, conformal coatings made with Elvacite® 2046 are more easily reworked, as they permit a greater number of solvents that can be used. This property is crucial for higher-value PCBs to ensure coatings are properly applied during manufacturing and is also helpful when the circuit board needs to be serviced. Additionally, Elvacite® 2046 is soluble in hydrocarbon solvents such as VM&P naphtha and some mineral spirits, enabling more economical formulations.
Elvacite® 2045
Elvacite® 2045 resin is based on an iso-butyl methacrylate polymer and offers many of the same benefits as Elvacite® 2046. However, it provides better hardness, strength, and abrasion resistance at the expense of slightly lower flexibility. Therefore, it is recommended for circuit boards that are more rigid or require greater physical protection.
Elvacite® 4349
Elvacite® 4349 is Mitsubishi’s newly developed methyl methacrylate/butyl methacrylate copolymer resin specifically designed for improved adhesion to metals, such as copper, aluminum, zinc, tin, brass, and stainless steel. It is commonly used in automotive, container, marine, and industrial coating applications where resistance to corrosion and weathering is critical. As PCBs feature copper and aluminum as part of their construction, Elvacite® 4349 is a good choice for maximum adhesion to these parts to protect against damage from exposure. Elvacite® 4349 is soluble in solvents such as toluene, MEK, acetone, ethyl acetate, dimethyl carbonate, and PCBTF.
Elvacite® Grade Overview
| Grade |
Acrylic Polymer |
Glass Transition Temp, Onset, °C |
Molecular Weight |
Acid Number (mg KOH/g Resin) |
Key Attributes |
| Elvacite® 2046 |
Iso-butyl/n-butyl methacrylate copolymer |
33 |
200,000 |
0 |
Broad solubility and better flexibility |
| Elvacite® 2045 |
Iso-butyl methacrylate |
48 |
260,000 |
0 |
Broad solubility and higher hardness |
| Elvacite® 4349 |
Methacrylate copolymer |
48 |
60,000 |
3.4 |
Excellent metal adhesion |
Since acrylic resins like Elvacite® are soluble in a wide variety of organic solvents, ideal use cases for conformal coatings made using Elvacite® include those that avoid potential exposure to solvents and solvent vapors. Therefore, circuit boards for consumer electronics, electric vehicles, and electronic displays are best, whereas aerospace and gas-powered automobiles, which emit fuel vapors, are not recommended.
Preparing Solutions with Elvacite®
Regardless of which Elvacite® resin is chosen, a few starting tips can help with coating formulation. Elvacite® resins are sold in bead form and should be mixed into solvents under constant agitation to prevent agglomerates from forming. The beads must be added directly into the vortex created by a mixer to facilitate good wet out and dispersion.
This mixture should be mixed under low-shear agitation between 1 and 12 hours, depending on the grade and concentration of resin used, until the solution appears clear in the mixing tank. To validate that mixing is complete, a sample can be taken and spread on a Leneta card or glass to allow the solvent to evaporate and form a film. Additional mixing is required if any resin seeds appear. Heating the mixture or mixing with higher shear can reduce solution time, as long as care is taken to prevent overheating, which leads to solvent loss.
Summary
Elvacite® resins are ideal for acrylic conformal coating formulations because they form films providing superior protection, high dielectric strength, and excellent clarity and adhesion to printed circuit boards (PCBs). Multiple grades of Elvacite® are available to enable conformal coating formulators to customize the degree of flexibility and solubility profile of their coatings or optimize adhesion to various PCB parts. Click below to request a sample of Elvacite® today and speak with one of our coating product experts.
