Fatigue measurement setup under combined thermal and vibration loading on electronic SMT assembly

In this work we introduce an experimental setup for experiments on combined thermal and vibration loadings applied to surface mount technology electronic systems. The setup provides well-defined load conditions and the ability of in-situ load measurement. Furthermore, rigging-free or known-rigging specimen mounting is featured. A test vehicle and an according mount as well as in-situ measurement approaches were developed and tested. This novel setup offers test vehicle mounting options which either reproduce system conditions including rigging for qualification purposes or enable fatigue research which rely on constant rigging-free load conditions. Specimens are made of standard or high temperature FR4 with assembled SMT components. Typically, vibration experiments will be conducted as a sine dwell with constant amplitude and frequencies in the range of 50 Hz... 1 kHz. The setup may be used for isothermal vibration experiments at room, lower or higher temperatures (e.g. -40 degrees C or 125 degrees C) but it enables vibrations experiments at temperature cycling conditions as well. A low weight mount and proper PCB design targeting temperature cycling with reasonable gradients of about 1 K/min. A certain specimen design with integrated PCB heaters even enables local component heating. Dependent on the temperature conditions either optical or capacitive contact-free in-situ measurements of the specimen displacement and deflection can be utilised respectively. The ability of conducting contact-free measurements is very important for small or low weight specimens. Bulky and heavy acceleration sensors add to much mass and change the deformation behaviour. Strain gages do not come with these drawbacks but require large mounting area and are difficult to mount reproducible. Using the contact-free measurement systems high spatial and time measurement resolution can be achieved. First experiments on solder joints of chip resistor components show the effect of temperature on solder joint damage under vibration loading. Increased temperatures increase the risk of vibration caused damage in SnAgCu solder joints.