Vibration Test and Shock Test of PCB Boards

Vibration test is an assessment The ability of the product to withstand the vibration environment (with different vibration levels), to check and analyze the defects of the product in terms of vibration resistance in design and manufacture, in order to improve the design and manufacture, to ensure the reliability of the product in use and transportation, is an important PCBA test part.

The vibration test is performed in the laboratory to simulate various vibration environments, and the sample is fastened on the special fixture of the PCB vibration table. The test can be divided into The vibration experiment with a fixed frequency is called a fixed frequency vibration test; the other is a vibration test with a logarithmic frequency conversion, which is a frequency conversion vibration test or a scanning vibration test. The fixed frequency vibration test is carried out according to the vibration test standard specified in the technical conditions of the product, and its frequency, vibration acceleration, vibration direction (can be one, two or three directions) and vibration time are carried out. The vibration time can be extended when fatigue damage occurs under the action of vibration stress.

The frequency conversion vibration experiment is from low frequency to high frequency, and then from high frequency to low frequency (the frequency is continuously changed in a logarithmic manner) as a cycle, called for one scan. The time and number of cycles, the frequency range and the vibration direction are specified in the technical conditions according to the use requirements of the product. During the scanning vibration test, it is necessary to observe whether the test sample has resonance phenomenon, and the destructive effect on the product structure during resonance.

Impact test is a test that tests the ability of a product to withstand impulse shock and non-repetitive shock during use and transportation, and is used to determine that the product is subjected to mechanical shock adaptability and the firmness of its structure.

When the impact is applied, the kinetic energy is transmitted to the product in the shortest time. The magnitude of the impact force can be expressed by the impact acceleration, which can also be expressed in units of the acceleration of gravity g. The shorter the impact time and the greater the impact acceleration, the greater the damage to the product. When the waveforms are different, they correspond to different spectrums, and different spectrums will have different effects on the product. Duration describes the length of the impact time. Under the same conditions, the longer the duration, the greater the impact on the product.

The simulated impact test in the laboratory is to fasten the product on the special fixture of the (non-working) PCB impact test bench. of. The shock pulse of the shock machine can be a terminal peak sawtooth wave, a semi-sine wave and a trapezoidal wave. For various shock pulse waves used in the test, the pulse peak acceleration and pulse width (duration) are specified by relevant standards. During the test, the three mutually perpendicular axes of the sample were continuously impacted three times in the positive and negative directions, for a total of 18 times.

The free drop test is also the simplest impact test. It is generally used to test the strength of the packaging structure by raising the packaging to a height of 0.5 to 0.8 meters above the ground. Then let it fall freely and impact on the rigid concrete floor. The impact position and times of the sample are specified according to the product technical requirements in the PCBA scheme.