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I need to create a PCB with a transformer on it, and in this case, I unfortunately can't solder on a regular one. I was wondering if there was anything akin to a 2d transformer, or just generally a coil I could print onto my PCB. I know that spirals are used in Radio-Applications, but I'm not sure if you could use something like this as a regular coil.

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    \$\begingroup\$ Planar transformers? \$\endgroup\$ – a concerned citizen Mar 18 at 10:45
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    \$\begingroup\$ Transformers do need to have 3 dimensions and at least two coils. There is no such thing as a "regular" transformer. \$\endgroup\$ – Andy aka Mar 18 at 10:46
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    \$\begingroup\$ Planar transformers are possible with multilayer IC or PCB, but performance is similar to air-core transformer of just a few turns, with very limited inductance and LI2 energy storage and lower coupling compared to the more commonly used ferrous core transformers. \$\endgroup\$ – MarkU Mar 18 at 11:45
  • \$\begingroup\$ Note you can obtain ferrite "cores" to use around PCB traces, which does improve characteristics somewhat. But this is a niche role, not suited to general-purpose use. \$\endgroup\$ – rdtsc Mar 18 at 11:57
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    \$\begingroup\$ you can use a planar transformer but it isn't cheap (you need many board layers usually) \$\endgroup\$ – Lorenzo Marcantonio Mar 18 at 12:08
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They are called "Planar transformers" and they are used in the Telecom industry.

https://www.electronicproducts.com/wp-content/uploads/passive-components-magnetics-inductors-transformers-wcjh-1s-jan201618.jpg

They need a multi-layer PCB because the windings are PCB traces. In the following picture you can see the multi-layer structure of the PCB.

I saw, time ago, a planar transformer printed on a 24-layer PCB.

https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Planar_Transformer.jpg/1024px-Planar_Transformer.jpg

The soft-ferrite core is than manually added by the worker after the PCB gets populated.

Often, they are manufactured and sold as single products. That is, it's very rare that people print planar transformers on the very same PCB of your final product.

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Maybe it's a matter of semantics, but what people are calling planar transformers here(or more generally, planar magnetics) we refer to as embedded magnetics.

Planar magnetics, as we use the term, is still a discrete component that is mounted to a PCB. What makes it a planar magnetic is that the windings are all in the same plane. The pictures below illustrate this technology.

This is an expanded view of a typical planar transformer.

enter image description here

It then gets dropped into a cutout in the PCB and the leads solder to pads on the board. See picture below.

enter image description here

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