µHPC/GA Contactors Operation

 
  • Precise DUT alignment is critical for high first-pass continuity yields and overall test yields.
  • The µHPC/GA uses several levels of DUT alignment: coarse, intermediate, and final.
  • The initial, or coarse, stage of alignment is achieved by using the wall of the guideplate in the DUT pocket to align to the outside edge of the device. Typically, this wall will also have a tapered lead-in feature.
  • The intermediate stage of alignment involves using a chamfered contact element hole. This feature will align the DUT over the contact element by guiding the solder ball of the package. The presence of this feature is package dependent and may not be incorporated within all contactors.
  • The final, or direct, stage of alignment for devices with solder balls is achieved by using the contact element itself. There are two primary methods for achieving this type of direct alignment:
    • The crown-top contact element is designed to be oversized and presents the largest possible target for the solder ball of the BGA device. The ridges of the crown-top element taper down from the points of the crown to the center of the element, and act to center the DUT.
    • The bored contact element uses a circular bore in the end of the element to provide self-centering, final alignment to the solder balls.
  • Both of these contact element types utilize sharp edges for contacting the DUT and penetrating oxides.
  • Devices that do not have solder balls must be aligned by using the outside edges of the device. In this case, ECT will analyze the package tolerances to confirm that successful testing is achievable.
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