New Magnetic Shielding Material - Page 1
Forum section: electronics / general

author: MegaVolt
author_rank: Frequent Contributor
timestamp: March 30, 2021, 11:07:01 am
content: 3M™ Flux Field Directional Material (FFDM) EM80KM is a multi-layer construction consisting of primary inner softmagnetic foil layer(s) with a top black film layer and an acrylic pressure sensitive adhesive (PSA) that provide manyspecial features.Key Features• High permeability magnetic foil• Approximately 80,000 permeability maximum• Thin overall construction• Pressure sensitive acrylic tape for high adhesion• Supplied on a removable liner for easy handling• Custom sizes may also be availablehttps://multimedia.3m.com/mws/media/875499O/3mtm-flux-field-directional-material-em80km.pdf

author: Kleinstein
author_rank: Super Contributor
timestamp: March 30, 2021, 11:22:15 am
content: I think they kind of cheated with the EM80 foil:The main difference between the case with the EM60 and EM80 foil may be that the EM80 fail is only a relativel small strip, about 1/3 the width of the sheet. This gives a magentic unisotropy and this way a preferred position to the rotor.A thin high permeabilit foil can still be good for magnetic shielding, but only for weak fields. With strong external fields one needs a material with enough saturation magnetization, more like steel. So the demonstration is a poor example.

author: TimFox
author_rank: Super Contributor
timestamp: March 30, 2021, 01:51:48 pm
content: Magnetic shielding with permeable material does not absorb the applied field, it re-directs the flux lines around the volume being shielded.When designing the shield structure, calculate how much area will "capture" the applied field, and how much magnification will result from the flux being confined to a thin region as it goes around the shielded volume. This, to first order, is only a geometric problem: the permeability of the material enters into the next stage where you calculate how much field will "leak" into the shielded volume. But first, you must ensure that the "captured" flux density in the permeable material does not reach the saturation flux density ("B field"), which isveryroughly 20 kG for iron alloys and 6 kG for nickel alloys. Sometimes, you need to put an iron alloy in an outer layer with a nickel alloy in an inner layer so that the nickel alloy does not saturate: nickel alloys have higher permeability, so when they don't saturate they result in lower fields inside the shielded volume.

author: jonpaul
author_rank: Super Contributor
timestamp: March 31, 2021, 01:28:30 pm
content: See the fine papers and specs from the original sources of these foils, Perfection Mica, the Netic and Co-Netic.Unsure how this new material differs from these, that have been available since 1941https://www.magnetic-shield.com/Bon chance,Jon

author: Kleinstein
author_rank: Super Contributor
timestamp: April 01, 2021, 05:34:02 am
content: I don't think the 3M material is much different. There is not that much choice for shieldung materials:When high saturation is important, that is electric steel (like transformer cores) - this is also relatively cheap.Classical permalloy type alloys have high µ, but relatively low saturation. It is available in many forms, but mechancally sensitive and soft: bending will reduce the permebility and may requite repeating annealing. It is also relatively expensive.As a relatively new option there are amophous and nanocrystalline foils with similar permeability to permalloy, but higher saturation. These are mechanically less sensitive (the nanocrystalline type may break). It is quite hard and thus more spring like and available only as a thin (some 30-50 µm) foil with limited width. With the higher saturaion the foil would corresponds to about 2 times the thickness of permalloy with half the permeability. Multiple layers with a spacer can compensate for a lower µ.Price wise I would expect it to be comparable to permalloy.The 3 M material may use the amophous material, maybe even 2 layers, but it could be as well permalloy. The new seems to be the glue.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: April 01, 2021, 09:36:29 am
content: Quote from: shodan@micron on April 01, 2021, 04:04:55 amI didn't say he was the best. I just drew attention to the fact that he appeared. How much better he is, I find it difficult to say. In my opinion, the presence of an adhesive layer is convenient. If it still tolerates bends well, then it is generally excellent.

author: jonpaul
author_rank: Super Contributor
timestamp: April 01, 2021, 01:47:59 pm
content: Hello again the technique for wide range shield is to use BOTH Netic and Co-Netic foil in layers.See the Perfection Mica app notes.Again very old technology!Jon