Design of a vibration positioner for ICs
In a test handler, semiconductor devices are reloaded between different containments several times. Because the containments have different grid tolerances, the ICs have to be fine positioned after reloading them into grids with smaller tolerances. A suitable oscillating conveyor should be developed in order to realize this fine positioning.
In a first step, a suitable vibration exciter was chosen. In the present case a pneumatic piston vibrator was selected. A directed transport is achieved by the incline of the piston axes with respect to the plate normal.
Additionally, the dynamic behavior of the swinging plate was designed. In order to achieve a uniform vibration transport, the bending and torsional natural frequencies of the swinging plate should be well above the frequency range of operation. A suitable decoupling between swinging plate and remaining structure should ensure that the rigid body natural frequencies of the swinging plate are well below the frequency range of operation.
The mid figure shows the frequency dependence of the vertical acceleration at several positions on the swinging plate. Within the frequency range of operation, the vertical acceleration is mostly independent of the position on the plate. This guarantees a uniform transport.
Finally, time-step simulations of the transport mechanism were performed for several values of static and sliding friction between IC and swinging plate. By this means, the resulting transport velocity can be estimated and the optimum inclination of the piston vibrator can be determined. The bottom figure shows the temporal course of the IC horizontal transport. Already after approx. 480 [ms] the maximum transport distance of 3 [mm] is reached.
The vibration positioner straightaway fulfilled all requirements in prototype tests. By default, new test handlers are equipped with it.
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Michael Elbs, Managing Director
Design / FEA model of the vibration positioner
Frequency response of the vertical acceleration at several positions on the swinging plate
Horizontal movement of the swingin plate (green) and resulting temporal course of the horizontal IC transport (red)