PCB standard for quasi-measurement of disturbance resistance

- Nov 03, 2018-

The purpose of this test is mainly to verify the resistance to the electrostatic discharge (ESD) caused by the approach or contact of an object or person or device.The internal energy of an object or person accumulates to an electrostatic charge of more than 15kv.Experience has shown that many unexplained failures and damage are likely to be caused by ESD.

Test instruments (EUT) capture ESD activity by discharging from the ESD simulator to the surface and near the EUT.Discharge severity levels are clearly defined in product standards prepared by the manufacturer and in EMC test plans.The EUT checks for malfunction or interference in all its operating modes.Passing/failing standards must be defined in the EMC test plan and determined by the manufacturer of the product.

PCB resistance transient conductivity (PCB resistance transient conductivity (EFT/B))) IEC 1000-4-4

The purpose of this test is mainly to verify the EUT's resistance to the transient short duration impact that may be generated by the inductive load or the contactor.The nature of the rapid rise time and repetition of such test pulses results in these spiking signals that easily penetrate the EUT's circuits and may interfere with the EUT's operations.The capacitance of the transient acting directly on the total power supply and signal line.

In other PCB spoiler tests, the EUT should be monitored as per pass/fail criteria using a general operational configuration.

PCB anti-electromagnetic radiation PCB anti-electromagnetic radiation PCB anti-electromagnetic radiation EC 1000-4-3

The purpose of this test is to verify the product's PCB immunity against radio, transceiver, mobile GSM/AMPS, and various electromagnetic fields generated from industrial sources.If the system is not shielded, electromagnetic radiation can be coupled to the interface cable and enter the circuit through the conduction path.Or it can directly couple the wiring of the printed circuit.

When the radiofrequency electromagnetic field is large enough, induction voltage and demodulation carrier can affect the normal operation of the device.

Run of PCB radiation resistance test

This test run is usually the longest and most difficult, requiring very expensive instruments and considerable experience.Compared with other

The PCB harassing test must be delivered to the test room with the success/failure criteria defined by the manufacturer and a written test plan.When feeding EUT into a radiation field, EUT must be set in normal operation and the most sensitive mode.

Normal operation must be established in the test room when the EUT is exposed to the graded interference field with frequency beyond the required frequency range of 80MHz to 1GHz.Some PCB anti-interference standards start at 27MHz.

Severity level

This standard usually requires 1V/m, 3V/m, or 10V/m for PCB immunity levels.However, equipment specifications may have their own requirements on specific "problem (interference) frequencies".How the product's PCB antiradiation level is appropriate is of interest to manufacturers.

Uniform site requirements

The new PCB immunity standard en50082-1:1997 cites IEC/ en61000-4-3.IEC/ en6100000-4-3 requires a uniform test environment based on test samples.The test environment is achieved in an echo free room with a tile arrangement of ferrite absorbers, which is used to block reflection and resonance so that a uniform test site can be established indoors.This overcomes the sudden and often unrepeatable test errors in conventional unlined rooms due to reflection and field gradients.(the semi-anechoic room is also an ideal environment for measuring the emission of radiation in an indoor abnormal environment requiring precision).

RF absorbers shall be arranged on walls and ceilings of semi-echoless rooms.Mechanical and RF design specifications should be adapted to the heavy ferrite tiles that line the roof of the room.The ferrite tile sits on the dielectric material and attaches to the top of the room.In unlined rooms, reflections from metal surfaces cause resonance and standing waves, which produce peaks and troughs in the strength of the test space.The field gradient in the usual unlined room can be as high as 20 to 40dB, and this will cause the test sample to appear to fail suddenly in very low fields.Room resonance causes low test repeatability and high chance of "overtesting".(this may lead to product overdesign) the new on-site equivalent of the PCB anti-interference standard iec1000-4-3 makes up for these serious deficiencies.

Generate test site hardware and software requirements

High-power broadband RF amplifiers are used to drive wideband transmitting antennas with frequency ranges beyond 26MHz to 2GHz, which are 3 meters away from the device being tested.Fully automatic testing and calibration under the control of the software achieves the best operation, providing greater flexibility for testing and full control of all key parameters, such as scanning rate, frequency pause time, modulation and field strength.Software hooks allow synchronization of monitoring and functional stimuli to EUT.Interactivity is required during actual testing to implement real-time changes to EMC test software and EUT parameters.This user access feature allows for quick recording of all data for efficient evaluation and scoring of EUT EMC performance.

The traditional pyramid absorber (cone) absorber is effective, but the large pyramid size makes it impossible to test the small available space in a room.For a lower frequency of 80MHz, the length of pyramid absorber should be 100cm, while for a lower frequency of 26MHz, the length of pyramid absorber should be over 2m.Pyramid absorbers also have disadvantages. They are fragile, easily damaged by collisions, and flammable.Using these absorbers on the floor of the room is also impractical.Due to the heat generated by the pyramid absorber, the field strength greater than 200V/m will be at high risk of fire after sustained over a period of time.

Ferrite tile absorber

Ferrite tiles are space effective, however they add significant weight to the roof, walls and doors of the room, so the mechanical structure of the room becomes very important.They work efficiently at low frequencies, but when the frequency is higher than 1GHz, they work relatively inefficiently.Ferrite tiles are very compact (100mm x 100mm x 6mm thick) and can withstand field strength over 1000V/m without risk of fire.

Difficulty in testing PCB for radiation resistance

Since the auxiliary equipment used to operate the EUT provides stimulus signals to monitor its own performance, it must itself be anti-interference to the sensitive field of the PCB, which is inherently difficult to run radiation sensitivity tests.This often leads to many difficulties, especially in the case of complex ancillary equipment, which requires many cables and interfaces to the EUT through perforated test rooms.All cables running through the test room must be shielded, and/or filtered to make the test field shielded from any degradation in the shielding performance of the test room.Compromise on the performance of the test room shielding will cause the test field to leak unintentionally into the surrounding environment, which may cause interference to those who use the spectrum.RF filters that use data or signal lines are not always feasible, such as when data is very large or when high-speed data links are used.