The vibration test simulates shocks upon the product resulting from transportation, installation and use environments, so as to verify if the product is sustainable to various vibrations. This test is especially important for testing vibration sustainability of automobile electronics.
Most frequently employed vibration types are Sine Vibration and Random Vibration. Sine Vibration is used to simulate marine vibrations for verifying sustainability of vessels, and for performing Resonance Analysis of the product structure and verifying the Dwelling Resonance of resonance frequencies. Random Vibration is used for assessing vibration sustainability of the integral structure of product and simulating transportation conditions in packaged state during the delivery.
For verifying system/module products, USA customers tend to employ ASTM, ISTA and MIL STD standards, while Japanese and European customers are familiarized with EN, IEC, ETSI and JIS standards. For testing IC components that are light weighted and compact in size, high-frequency vibration is used in comply with MIL STD standards.
Product damage occurs when the stress induced by environmental vibration exceeds the sustainable stress of the structure; if the structure is excited by the environmental vibration in its natural frequency, a resonance amplification will occur, bringing utmost devastation to the structure. In fact resonance amplification is a major cause for product damage, therefore when carrying out vibration tests, Sine Vibration is normally used in combination with an FFT Analysis to analyze the resonance frequency of the structure, with resonance dwell verified at the same time to ensure that the structure is strong enough to sustain the Fn excited by the environmental vibration.
This data is helpful for product to structure designer into understanding weak points of the structure and taking corresponding improvements.
Requirements to sustaining vibrations are much stricter in automotive electronics than in consumer products. SAE of USA, JASO of Japan and IEC of EU have suggested specifications and testing methods. Active and passive automotive components are mostly tested based on AEC standards.
Mechanical Shock Test
Consumer products usually encounter two kinds of shocks in the lifespan; one is Bumps caused by vehicles on bumpy roads during the transportation, the other is Drops caused by loose cargo or human negligence in handling the goods. Hand-held products such as cell phones and PDAs are more vulnerable to dropping impacts when no buffer protection is provided. Automotive electronics work in a much adverse environment than consumer products; especially when they are installed at tires, doors or trunks that sustain to more severe vibrations. The Mechanical Shock Test, which offers prompt verification of structural strength in the product design stage for deciding whether proper buffering is required in the packing design, is one of crucial items for validating the design.
International Electrotechnical Commission, also known as IEC, provides basic conditions for shock tests as shown in Table-1 addressing systems/ module products that are less likely to encounter shock stresses in their lifespan. In the past, shock tests were mostly carried out usingwith half-sine wave as the shock wave form, however this is substituted by square waves in recent years. Tests were carried out with the product unpacked; impacts are exerted in 3 axes (6 faces), with 3 impacts in each face. It is suggested that at least 3 specimens shall pass the specified impact conditions.
At the same time, basic test conditions of bump tests on systems/ modular products more likely to sustain successive shocks in their lifespan are shown in Table 2. Bump tests are categorized in packaged and unpacked conditions. Most automotive electronics are verified for their quality by bump tests. Bump tests are carried out in three axes (6 faces); number of bumps per face varies according to different specifications (see Table-2).
Frequency range：1 to 2000 Hz (bare table) Sine wave
Max force output：5000Kgf (11023 lbs.)
Max velocity：78 in/s(2 m/sec)
Horizontal slip table：70*70/cm、150*150/cm
Digital vibration controller 8CH
Mechanical Shock Test
Pulse shape：half-sine and trapezoidal wave
Pulse duration：0.1 to 65 ms