How to bond phenolic – Successful phenolic bonding
What is phenolic and how to bond phenolic?
Phenolic is a hard dense material made by applying heat and pressure to layers of paper or fabric impregnated with phenolic resin. Phenolic paper is a type of composite used for PCBs (printed circuit boards). It is also known as FR-1 or FR-2. The FR1 has a 130C rating and FR2 has a rating of 105C. Both FR1 and FR2 are used for single layer PCBs. There are several options used to bond phenolic and the choice is dependent upon additional requirements of the application like electrical properties or thermal properties.
Phenolic is available in rod and tube also. Since this material is so hard it is machinable with tools used for wood or soft metals.
What about FR4? FR4 is not phenolic based but an epoxy based composite which is very popular for multilayer boards. FR4 is likely the most popular type.
How to bond phenolic?
Phenolic is fairly easy to bond therefore there are many adhesive types are available (and listed below). When it comes to PCBs there are several points to consider in addition to adhesion. Most importantly:
- Electrical Properties
- Thermal Conductivity
- Heat Resistance
- Non-corrosive Nature
- Flame Resistance
Review these points with an adhesive specialist.
For structural applications of rod and tube properties to take into consideration may include:
- Impact Resistance
- Solvent Resistance
- Environmental Resistance
Cyanoacrylates: All grades bond well. For low odor chose a 94x product. For high-temperature resistance choose 820.
1 and 2 component epoxies also bond well. For heat cure epoxies, check the temperature rating of the phenolic to ensure you stay within its limits. ES578 offers flame resistance and good thermal conductivity as well as good electrical resistance.
Structural acrylics bond phenolic well – consider a non-corrosive, methacrylic acid-free formulation such as TA439 and TA4590. Permabond TA4392 offers flame resistance and good thermal conductivity.
UV curable adhesives bond well, providing light can reach the bond. For coating and doming consider UV681 and UV683.