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The BIG ISSUE of the NFC Coil Micro-short Product!

Why is a contactless IC Card not responding or taking a prolonged duration to align before it can be sensed?

There is an IC chip in every card. The IC sends out a signal by means of received energy, where the better the resonance, the faster the transmission. A near field frequency that is too far away to receive. If the resonance frequency is offset, the credit card/cell phone (the transmitting end) may require multiple sensing swipes or being placed in an optimal position to be detected.

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For ensuring NFC sensitivity, the importance of coil production and testing increases drastically.

NFC coils may be subject to variations due to minor alterations in the production process, therefore the manufacturer needs to carry out more stringent inspection and tests to ensure NFC products work smoothly. The NFC card comprises a near field communication coil. The current generated by this coil may damage IC data, burn the IC or burn the coil, therefore causing a micro-short-circuit which causes an inferior resonance frequency and consequently results in disability of signal reception. Conductance/Capacitance is the most fundamental condition. More concentrated resonance produces more concentrated transmission. A series connection of resistance affects the power consumption.


Inductance, Problem-1 in PCBs/FPCBs: 

Using copper foil coils and multi-layer lamination to replace the traditional coils with a large form factor is a new technology. However the process is prone to defects caused by factors including etching solutions, timing, insulation coating and pressure. The size of the copper coil will affect its inductance. PCB production or coil winding is susceptible to coating peel off or scratching, which will result in short-circuiting. The first effect of this kind of a micro-short is to the Inductance L. Reduction in Inductance will cause shifting of the resonance point.

Capacitor, Problem-2 in PCBs/FPCBs:

The magnitude of pressure during the lamination affects distribution of capacitance, and this parameter also alters along with the temperature, therefore changing the value of capacitance. When capacitance is changed, the resonance frequency also changes accordingly. This results in deterioration of the resonance frequency and inability of signal reception.


Problem-3 in PCBs/FPCBs:

Poor PCB materials. Factors such as poor copper foil coefficient, uneven thickness of the entire piece of material, excessive tensile inflection of flexible board, etc. will result in uneven quality of products in a batch, therefore low in yield.

Near Field Communication

Also known as Short Distance Communication or Near Field Communication, an NFC is capable of non-contact point-to-point data transfer between a transmitting end and a receiving end. It has a package of communication protocols that also allow the device to read an NFC tag that contains product data.

Principle of resonance frequency

Higher Resonance Frequency transmits higher energy. It’s like the sound in a large room that echoes with a loud resonance. For instance:

[In the figure on the left] The cell phone transmits 100k resonance frequency, if the receiver has a resonance frequency of 110K, the sensing quality of this signal will be not so good and data will transmit poorly. A data error will likely occur. For a successful transmission, the two devices will need to be very close to each other or several transmissions will be required.

[In the figure on the right] The cell phone transmits 100k resonance frequency, if the receiver has a resonance frequency of 101K, the sensing quality of this signal will be good and data will transmit nicely. For a successful transmission the two devices will only need to get slightly close to each other, or a quick pass will do.


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