Board-level cyclic bending test
Board Level Cyclic Bend Test is a test used to evaluateThe fatigue life and reliability of surface mount device (SMD) solder joints under repeated bending stress.the mechanical durability testing method, belongs toBoard Level Reliability (BLR)One of the important verification items.
In practical applications, electronic products often due tooperational behavior, structural stress or external environmentand withstand long-term, low-frequency but repetitive bending loads, such as mobile phone key operations, laptop opening and closing, automotive module vibrations, and fixed structure deformations, etc.這類重複性彎曲will cause the solder joints to gradually accumulate fatigue damage, ultimately leading to crack propagation, instantaneous disconnection, or permanent electrical failure.
The Board Level Cyclic Bend Test simulates the aforementioned usage scenarios through controlled bending amplitude and cyclic frequency, assessing the durability of solder joints under long-term fatigue stress, focusing onFatigue life of solder joints under long-term repeated bending stressThe key reliability testing method, MA-tek follows the JEDEC international standards, combining precise bending control and real-time electrical monitoring technology, assisting customers in grasping solder joint fatigue risks during product design and mass production stages, and comprehensively enhancing the long-term reliability and product quality of PCBA.
The main purposes of the board-level cyclic bending test include:
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Evaluate the fatigue life of SMT solder joints under repeated bending stress.
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Analyze the aging behavior and failure modes of solder joints under cyclic bending conditions.
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Comparing the sensitivity of different solder alloys, packaging forms, and PCB structures to fatigue stress.
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Provide important basis for product structure design, material selection, and reliability verification.
This test is particularly suitable forportable electronics, wearable devices, automotive electronics, and high-reliability modules。
The Board Level Cyclic Bend Test is generally based onJEDEC JESD22-B113 (Board Level Cyclic Bend Test Method)The specifications define the geometric configuration, cyclic conditions, displacement control methods, and failure criteria for the bending test, ensuring that the test results are consistent and comparable.
Figure | Board Level Cyclic Bend Test (JESD22-B113) Four-Point Bend Test Configuration Schematic
Test Method | Application of Cyclic Loads under Four-Point Bending Structure
Board Level Cyclic Bend Test is usually conducted using4-Point BendStructure. During the test, the circuit board is fixed and supported on both sides (Support Span), and bending loads are applied by two movable force points from above (Load Span), creating a stable and repeatable bending stress distribution in the central area of the PCB. The test is conducted withDisplacement control or strain control methodProceed to apply bending deformation repeatedly at a fixed frequency, causing the solder joints to endure alternating tensile and compressive stresses, gradually accumulating fatigue damage.
Common test conditions are (actual conditions adjusted according to product application and testing purpose):
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Bending frequency: approximately1 Hz
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Bending displacement amplitude: about2 mm
Figure | Real-time resistance measurement curve of solder joints during testing, showing the difference between good solder joints and fatigue failure solder joints.
Real-time monitoring | Electrical measurement of solder joint fatigue degradation
During the entire cyclic bend test process, it is usually accompanied byReal-time Resistance Monitoring System (Multi Event Detector System, MEDS)Continuously measuring the resistance changes of solder joints to track the process of solder joints gradually entering fatigue failure from a healthy state, the real-time measurement curve can clearly present:
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The conductive behavior of stable solder joints under cyclic bending.
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The phenomenon of instantaneous disconnection or sudden increase in resistance caused by the generation and expansion of solder joint cracks.
Failure Determination Criteria | Definition of Electrical Failure of Solder Joints under Cyclic Bending
The failure determination of the board level cyclic bend test is usually based on the JESD22-B113 standard, and the determination method is: when the real-time resistance monitoring system detectsThe resistance value exceeds 1000 Ω in a single event.，且該事件首次出現在within 1000 bending cycles，並在隨後An additional 100 cycles occurred with at least 9 instances of resistance values exceeding 1000 Ω, with each instance lasting 1 millisecond (ms) or more.This allows for the determination of fatigue failure at the solder joint, and the rigorous assessment method can effectively eliminate momentary noise interference, ensuring that the failure results reflect the actual fatigue damage of the solder joint.
The practical applications of board-level cyclic bending tests in the industry include:
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Simulation of pressing and operating behaviors of mobile phones and wearable devices
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Reliability verification of repeatedly stressed products such as laptops and displays.
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Fatigue assessment of automotive electronic modules in driving and vibration environments
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Comparison of the durability of solder alloys, packaging structures, and PCB designs
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Early exposure of fatigue risk in solder joints before mass production
