Cables and connectors are the easiest and most difficult objects to test, and they usually have to be tested at the same time; An interconnect component that processes RF, especially tens of GHz signals, will be difficult to test… Why? Because everything will affect the performance, including setting, test instrument and setting, material, dimensional accuracy, bending, operation mode and so on.
There is another common connection scheme that should be easier to detect, that is, the widely used crimp connection (crimp); In principle, this connection is very direct, because the connector is squeezed onto the line with manual or electric auxiliary crimper, and the line and connector are deformed in plastic mode and closely combined into a pair, so they should be strong electrically and mechanically. If fabricated correctly, the crimp interconnection has the additional advantages of low impedance, reliability and relatively low cost.
There are many kinds of crimping connectors on the market, including fork and ring terminals; However, according to the experience of the author’s colleague, Martin Rowe, senior technical editor of EE ties / EDN, poor crimping connectors can lead to heating and even fire.
Paradoxically, although the crimp connection is completely visible to the naked eye, it is difficult to detect; Many factors can lead to errors, such as unevenly applied crimping force, misaligned lines, too much pressure (which may lead to small cracks in solid or standard lines), too little pressure (which usually leads to intermittent connections due to vibration), etc.
It is not appropriate to test the quality of the crimped link by disassembly or pull to failure test, because it needs to destroy the link itself; Disassembly can only be used for random testing of samples or to verify settings. So how do you test these links in a fast and non-destructive way? They are important link interfaces of the system, and reliability is very important.
In order to solve this problem, the Langley Research Center of NASA proposed a real-time ultrasonic equipment to judge whether the link passed the test with advanced signal analysis; The system (now licensed) transmits a sound wave when making a crimp connection.