Is there any way for SMT assembly to reduce failure issues?
SMT assembly refers to a series of technological processes applied to printed circuit boards (PCBs). PCBs, or Printed Circuit Boards, are essential components in electronics. So, is there any way for SMT assembly to reduce some common failure problems?
**SMT Assembly**
The manufacturing process, handling, and testing of printed circuit assemblies (PCAs) all subject the components to considerable mechanical stress, which can lead to failures. As grid array packages increase in size, determining appropriate security measures for these processes becomes increasingly challenging.
For many years, the monotonic bending point test has been a standard method for evaluating package durability. This test is outlined in IPC/JEDEC-9702, titled “Monotonic Bending Characteristics of Board Level Interconnects.” It describes the breaking strength of horizontal interconnections on printed circuit boards when subjected to bending loads.
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1. However, this test method cannot determine the maximum allowable tension.
2. For both the manufacturing and assembly processes, especially in lead-free PCA, a significant challenge is the inability to directly measure stress on solder joints. The most widely used metric for describing the risk to interconnected components is the tension on the PCB printed circuit board adjacent to the component, as outlined in IPC/JEDEC-9704 “Printed Wiring Board Strain Test Guidelines.
3. A few years ago, Intel recognized this issue and began developing a new testing strategy to simulate the worst bending scenarios. Companies like Hewlett-Packard also saw the benefits of alternative testing methods and started exploring similar approaches. As more chip manufacturers and customers understand the importance of determining tension limits to minimize mechanical failures during manufacturing, handling, and testing, this method has garnered increasing attention.
4. With the expansion of lead-free equipment usage, user interest has grown due to frequent quality issues.
5. As interest from various stakeholders increases, IPC has deemed it necessary to assist companies in developing test methods that ensure BGAs are not damaged during manufacturing and testing. This effort is being carried out jointly by the IPC 6-10d SMT Attachment Reliability Test Method Working Group and the JEDEC JC-14.1 Packaged Equipment Reliability Test Method Subcommittee, and the work has been completed.
6. The test method specifies eight contact points arranged in a circular pattern. The PCA with a BGA mounted at the center of the PCB is positioned with the component face down on support pins, and a load is applied to the back of the BGA. A strain gauge is placed adjacent to the part according to the recommended gauge layout of IPC/JEDEC-9704.
7. The PCA will be bent to the relevant tension level, and failure analysis will assess the extent of damage caused by the deflection at these tension levels. An iterative approach can determine the tension level that does not cause damage, establishing the ultimate tension limit.
