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Failure Analysis Experience and Validation in Automotive PCB(Printed-Circuit Board)

In recent years, the popularization of E-Mobility implementation and the rise of the IoT/IoV, a large number of electronic components have been applied to automobiles, and all relevant supply chains are actively approaching the market. PCB(Printed-Circuit Board) is a key part among these electronic components. In order to ensure highly reliable products, automotive PCB has to verify the quality and follows, not only the international standard IPC-6012DA, IPC (Association Connect Electronics Industries) issued for automotive PCB, but also specific requirements developed by various vehicle companies or Tier 1 suppliers.

In the experience of automotive PCB verification, DEKRA iST has surpassed general quality issues in PCB, via a couple of key validated tests, as below:


A. Connected Issue:The most commonly connected issues are Plating Through Hole (fig.1) and cracked Blind(fig. 2) or Buried Hole, causing an abnormal, electrical open circuit.


PCB-001.jpg
PCB-002.jpg
     Fig. 1 Cracked Plating Through Hole wall
       Fig. 2 Blind Hole cracked at the bottom
For the abnormal described as above, Thermal Shock Test (TST) could verify PCB’s potential problems caused by sudden exposure to temperature differences, the changing rate of contact resistance would not exceed the standard. As for automotive PCB verifies that in addition to the temperature change conditions, the current is increased to simulate the use state to make the test environment more stringent.

B. Insulation Issue: The most common issues resulting from poor surface insulation or abnormalities in process/materials are decreased insulation resistance to cause poor insulation. The extent of serious electrical anomalies caused by short circuits can be seen in fig.3 & fig.4.


PCB-003.jpg

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Fig.3 Abnormal Insulation between the surface traces
Fig.4 Conductive Anodic Filament(CAF)between via holes
The most common acceleration factors to verify for insulation include temperature, moisture and bias; in any kind of test conditions, the main purpose is to verify that the automotive PCB meets the required standard. Each component supplier for automotive PCB has the specifications and methods for the test. It is important to follow the standard and to ensure that your product and process abilities can meet high-reliability requirements; these are the goals of each company.

C、Delamination/Laminate crack Issue:The implementation of lead-free assembly process for automotive PCB is late, but it is a necessary process to commit the concept of environmental protection. During the transferring, the delamination and laminate crack issue of automotive PCB is the same as general PCB, therefore, the materials and processes of current automotive PCB must be adjusted to achieve high reliability.


PCB-005.png
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         Fig.5 Reflow simulation facility
  Fig.6 Delamination image of PCB through SAT

To verify the delamination of PCB, the reflow simulation test can be used to verify the heat resistance of the PCB. The key parameter of this method is the profile of the temperature of the reflow oven corresponding to the actual board temperature, as for the temperature requirement, IPC and IEC standards or the specification from the component suppliers can be followed. Another important point is the inspection method after reflow simulation, includes visual inspection or SAT (Scanning Acoustic Tomography) could find the abnormal spot, these are for non-destructive analysis. Then the next step could use destructive analysis (Micro-section)  find the abnormality and root cause to improve PCB manufacturing process.

As for automotive PCB verification, DEKRA iST has rich experience, not only offering the customer testing technology, but also expertise service and verification methodology planning etc.Contact Window | Mr Peng | Tel:886-5795766-7501 | E-mail :michael.peng@dekra-ist.com
Email: dirs.mkt@dekra-ist.com
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