Bobbin Series Guide
Which bobbin series CB Magnetics publishes, how many parts are in each, and the plastics used across them.
A bobbin series follows the core shape it is built for. Choosing the series is therefore a core decision before it is a plastic decision. The table below is generated from the 522 published part numbers in this catalogue, so the counts are what is actually available rather than a wish list.
| Series | Published parts | Most used materials |
|---|---|---|
| ATQ Bobbins | 35 | Phenolic |
| EE Bobbins | 42 | Phenolic, GFN, PET |
| EF Bobbins | 41 | Phenolic, PET, PET/GFN |
| EFD Bobbins | 20 | Phenolic; Pin Material: CP Wire |
| EI Bobbins | 35 | PBT, PA66, GFN |
| EP Bobbins | 20 | Phenolic, PM9630, LCP; Pin Material: Phos Bronze |
| EPC Bobbins | 17 | Phenolic; Pin Material: CP Wire, Phenolic PM9630; Pin Material: CP Wire, LCP E4008; Pin Material: CP Wire |
| EPX Bobbins | 4 | LCP |
| ER Bobbins | 45 | Phenolic, GFN; Pin Material: CP Wire, Phenolic PM9630; Pin Material: Phos Bronze |
| ETD Bobbins | 13 | Phenolic; Pin Material: CP Wire, Phenolic; Pin Material: CP Wire, Phenolic; Pin Material: CP Wire |
| PQ Bobbins | 54 | Phenolic, Phenolic, Pin Material: CP Wire, LCP, Pin Material: CP Wire |
| RM Bobbins | 23 | Phenolic; Pin Material: CP Wire, PET; Pin Material: CP Wire, Phenolic; Pin Material: CP Wire |
| UI Bobbins | 1 | GFN |
| SMD Base and Case | 70 | LCP, DAP (Black), PPS |
| Through Hole Base and Case | 61 | GFN, Phenolic, DAP |
| Silicon Steel Cores | 8 | — |
| Amorphous Cores | 2 | — |
| Nanocrystalline Cores | 1 | — |
| Low Frequency Transformers | 2 | — |
| RJ45 Transformers | 2 | — |
Reading The Table
A large count means a wide spread of sizes and pin counts inside that series, so a size change is likely to stay within existing tooling. A small count means the series exists but the geometry you need may be a tooling job.
Three Things That Decide The Series
- Height. EFD and ATQ shapes exist because the housing is short. ETD and PQ exist because the core volume has to be larger.
- Winding window. The window sets how many turns of your wire gauge fit before the build gets tight.
- Board footprint. Pin distance and row distance are published per part, so the land pattern can be drawn before samples exist. See the pin and footprint guide.
More From The Knowledge Center
Questions On This Topic
Which series has the most options
The PQ ER EE and EF series carry the largest number of published parts in this catalogue.
Can I mix a bobbin from one series with a core from another
No. The former is dimensioned for its core shape. Changing core shape means changing series.
What if my size is not published
It becomes a tooling job. See the tooling service.
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.