Material Guide
Thermoset against thermoplastic for transformer bobbins and toroid mounts, and which plastics appear across the CB Magnetics catalogue.
Plastics used in moulding toroid mounts and headers fall into two broad families, thermoset and thermoplastic. The difference matters most at the soldering step.
Thermoset
Thermosets include epoxies, phenolics and diallyl phthalate. They are known for environmental stability and for tolerating well over 750 degrees Fahrenheit without melting. That temperature headroom is what makes them the usual choice when self stripping magnet wire is used: the unstripped untinned wire is wrapped around a terminal moulded into a thermoset header and dipped into a solder pot at around 750 degrees Fahrenheit, which burns off the insulation, tins the wire and solders it to the terminal in one operation without melting the mount.
Thermoplastic
Thermoplastics include nylon, polypropylene, polycarbonate, polyester, LCP and PPS. They start to melt if held much above 500 degrees Fahrenheit for any length of time. The same chemistry that lowers the melting point also makes them cheaper to mould, which is the cost advantage.
The Trade Off
A thermoplastic mount costs less but the winding leads have to be pre-tinned, and heat has to be managed carefully when soldering the leads to the mount and the mount to the board. A thermoset mount costs more, but with self stripping wire several terminations can be soldered at once and the wire needs no stripping or pre-tinning, which can make the total cost of producing the component lower.
Materials Across This Catalogue
Counted from the published material field on every part number in this catalogue.
| Material | Parts |
|---|---|
| Phenolic | 192 |
| Phenolic; Pin Material: CP Wire | 43 |
| GFN | 40 |
| PBT | 33 |
| PET | 33 |
| LCP | 26 |
| DAP (Black) | 14 |
| PPS | 12 |
| Pin Material: CP Wire | 11 |
| Phenolic; Pin Material: CP Wire | 11 |
| DAP | 10 |
| PA66 | 8 |
| LCP(Black) | 6 |
| Phenolic; Pin Material: CP Wire | 5 |
Most parts also carry a UL 94-V0 flammability rating and Class F thermal rating where the drawing states one. More on what a thermoset actually is.
More From The Knowledge Center
Questions On This Topic
Which is better thermoset or thermoplastic
Neither in general. Thermoset if you solder with self stripping wire or run hot processes, thermoplastic if you can manage the heat and want the lower moulded cost.
What does UL 94-V0 Class F mean here
UL 94-V0 is the flammability classification of the moulded body. Class F refers to the thermal class of the insulation system.
Can I get the same geometry in a different plastic
Usually yes. The same tool can often run a different material, so ask before assuming a redesign is needed.
Turn This Into A Part Number
Send the constraint you are working against and you will get a part number or a tooling answer back.