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In this page, we will discuss the materials used in HDMI and its characteristics.
FPE Foam-PE with proportion 0.7g/mm³
Often use America material 3485 as the FPE, before foaming, the PE’s permittivity is about 2.3， PE after foaming, the permittivity comes down and the attenuation become lower while the transmit signal become better. the more complete the PE foaming, the lower the permittivity and the better the transmit, but the physical performance also come down. e.g: the hardness come down and the stretch become shorter. Normally, chemical foaming degree is about 30-50%, often use 40%. we use PE+ foaming agent to processing the FPE, foaming agent release lots of small foam after high temper , these small foam spread among the PE and then make the FPE. Often, the higher temper, the more complete foaming. Foam wire use in HF signal transmit.
HDPE 0.92-0.95g /mm³
Normally use America’s 3364 PE, use in electrical wire insulation, drain wire insulation, not use for foam PE. price is about 20% lower than 3485.
pvc 1.48g/mm³
low price,good insulation,anti-corrosion and easy processing. It has been widely used in cable jacket
TPE 0.9-1.25g /mm³
it is a kind of high elastic rubber,strong and elastic materials. It can be used in cable jacket, price is higher than PVC.
wire OD use ID (Inner Diameter)，middle diameter useMD，outer diameter use OD As the surface of the jacket, there are frosting, half-frosting, polished kinds.
Wrap material： Aluminum foil can also be abbreviated as AL, sometimes customers will write S.AL refers to single-sided aluminum foil, and D.AL refers to double-sided aluminum foil
AL/Mylar AL-Foil AL/MY with proportion of 0.05g/mm (experience data ) has characteristics as follow:
Use 12u aluminum layer and 10u PET transparent light film, plus 3u glued together, the total thickness is 25u. The confined metal space can shield signal interference/crosstalk. The aluminum foil wrapped (rolled) uses this principle to achieve the shielding purpose. The default overlap rate of the wrapped aluminum foil is more than 25% to ensure the shielding effect.
PET Mylar transparent film 0.04g/mm (experience data)
Generally used for insulation and isolation, without the shielding effect of aluminum foil or copper foil. The thickness is generally 20-25u
Al+ PET 0.09g/mm (experience data)
The above two materials are made together. PET is slightly wider than aluminum foil. The original process of wrapping aluminum foil and then PET becomes directly wrapping fin aluminum foil, that is, one process completes the work of the previous two processes, but fin aluminum foil is harder and more expensive. It is also more expensive than the combined materials of the above two processes, so there are not many applications.
copper foil
The shielding effect is better than that of aluminum foil, and the price is higher. Generally, the 360-degree copper-clad ring welding of the joint is shielded on the line that requires EMI. At present, it is also shielded by ring welding of tinplate. The thickness is generally 35u or 55u
ALMG al alloy ‘s proportion is 2.7g/mm³
The conductivity of aluminum is better than that of steel, and the conductivity is about 60%. However, the strength of aluminum is poor and easy to break. Adding a small amount of magnesium can strengthen its strength to a certain extent, and the price is about half lower than that of copper. The shielding effect is worse than copper. Weldability is poor (can’t be welded), usually need to add a BC/TC/CCS to weld on the joint shell to ground.
BC TC ‘s proportion is 8.9g/mm³
Like the previous conductor introduction, tinned copper and bare copper have similar shielding effects, which are much better than aluminum-magnesium wires. They are expensive and easy to solder. You don’t need to add a ground wire to solder. One group of braided nets can be drawn as the general ground wire welding.
As shown in the figure below, the red dot marks the intersection of the two strands of the woven net, counting straight to the right to the 9th intersection. The distance between 1-9 points is the pitch of the 16-spindle woven net. If it is 24 spindles, then Measure to the 13th intersection; The number of knitting mesh refers to the distance of one inch (2.54CM), and the number of intersections counted by the straight line is the number of meshes. The larger the weaving pitch, the smaller the mesh, the lower the shielding rate and the worse the shielding effect. At present, HDMI26/28 weaving 168 nets or more generally use 24 ingots to weave
In addition, because of the non-shielding effect of the cotton net or metal material net woven outside the wire, the function of the outer net is generally to be beautiful, wear-resistant, and tensile. Woven net is represented by B, +ADB in English: A is aluminum foil, D is ground wire, and B is shielded net
Take HDMI AM-AM as example 1-12 is for data and time channels，2/5/8/11 four pins is for earth wire 14/19/17 is for independent ethernet channel，17pin is for earth wire Normally, the earth wire use PE insulation If one group of signal wire has problems, we can connect them to the 14/17/19 Pin, in order to guarantee the image data. but if more than one group signal wire has problems, there would be nothing we can do about it.
