【国外标准】 Standard Test Method for Evaluating the Reliability of Surface Mounted Device (SMD) Joints on a Flexible Circuit by a Rolling Mandrel Bend (Withdrawn 2024)

4.1 The existing Test Method F1995, while very useful, is difficult to conduct if an encapsulating dome is applied, and does not reveal the possible failures caused by mechanical stress incompatibility in the overall SMT joint. This mandrel bend test will reveal possible mechanical stress incompatibility between the various adhesives which can result in latent field failures during production handling or with thermal cycling in normal use.4.2 The existing Test Method F2750 does not include specifics for SMD attachments and only addresses the conductivity change of the conductive trace.4.3 The different combinations of SMD types, attachment medias, circuit substrates and process variation can account for significant variation in test outcome.4.4 Bending of printed flexible circuit or their components can affect their visual appearance, mechanical integrity or electrical functionality. This test method simulates conditions that may be seen during manufacture, installation, or use.4.5 Bend testing may be destructive, therefore any samples tested should be considered unfit for future use.1.1 This test method covers a means to test a completed Surface Mounted Device (SMD) joint for bond strength and inter-layer stress compatibility1.2 A completed SMD joint includes; SMD (LED, resistor, etc), PTF ink land (typically silver), conductive adhesive (typically silver), staking compound (non-conductive), and encapsulant (non-conductive).