Camera based two-point vision alignment for semiconductor device testing handlers

1. A vision alignment system for a test handler, comprising:

a first camera, configured to view a position of a contactor in a handler coordinate system;

a pick-and-place handler, configured to move a tested device to the contactor for testing;

a second camera, configured to view a position of a device in a device holder coordinate system; two guiding features for correcting the position offset between the device and contactor; and

a guiding plate, having three actuators, configured to actuate the guiding features on the device holder to correct the position offset between the tested device and the contactor.

2. A vision alignment system for a test handler as claimed in claim 1 , wherein the device holder comprises:

a first guiding feature configured to move the tested device horizontally or vertically; and

a second guiding feature configured to adjust the angular position of the tested device.

3. A vision alignment system for a test handler as claimed in claim 1 , wherein the guiding plate comprises:

a first guide slot configured to adjust the tested device horizontally or vertically with two guiding surfaces and a spring to ensure touching between the guiding circle of the device holder and the guiding slot of the guiding plate;

a second guide slot configured to adjust the angular position of the tested device with one guiding surface and a spring to ensure touching between the guiding circle of the device holder and the guiding slot of the guiding plate; and

a locking mechanism configured to lock the guiding plate to the contactor after the guiding plate actuated at the correct position.

4. A vision alignment system for a test handler as claimed in claim 1 , wherein a double side visible training device with high contrast circle dot array is used as a training device to define a common coordinate viewed by the first camera and the second camera.

5. A vision alignment system for a test handler as claimed in claim 1 , further comprising:

a controller for controlling the operation of the first camera, the second camera and the pick and place handler;

a lighting system configured to provide high contrast lighting for the first camera and the second camera; and

a vision alignment processor, having a memory, configured to process images captured by the first and second processor in order to correct the position offset of the tested device.

6. A vision alignment system for a test handler as claimed in claim 5 , wherein the lighting system is a three-channel programmable LED array.

7. A vision alignment system for a test handler as claimed in claim 5 , wherein a lighting angle of the lighting system is in the range of zero to ninety degrees.

8. A vision alignment system as claimed in claim 5 , wherein the vision alignment processor is configured to execute vision alignment software configured to operate the vision alignment system according to desired user settings.

9. A method for calibrating a vision alignment system for a test handler comprising the steps of:

imaging a training device in a device holder with two guide features using a first camera;

recording the positions of the guide features on the device holder in a training device coordinate system;

moving a guiding plate to a contactor nominal position using three actuators;

inserting the training device on to the guiding plate with guiding slots;

locking the training device to the guiding plate and releasing the device holder from the guiding plate;

imaging and recording the position of the guiding plate in reference to the training device coordinate using the second camera; and

establishing a calibrated transform from the contactor nominal position to the device holder with the guiding plate and the three actuator nominal positions.

10. A method for aligning devices in a test handler, comprising the steps of:

providing a tested device on a device holder;

determining a position offset between the tested device and two guiding features on the device holder using a first camera;

using a pre-calibrated transform to determine the offset between the tested device and a contactor;

converting the offset to linear motion commands for three actuators to position a guiding plate; and

locking the guiding plate and inserting the device with device holder to the contactor through the guiding plate.