Technical Informer: USB Tweezers

Many bond strength tests require a means to grip the part so that the strength of its bond can be tested. Examples include solder ball pull (often referred to as CBP) and ribbon peel. The sizes of parts range from a few millimetres to tens of microns and the bond strength from several kilograms to one or two grams force. In many of these applications the geometry and force of the grip must be precisely controlled to ensure sufficient force can be applied to the bond but without the act of griping affecting the bond itself. To cater for this xyztec developed a new generation of tweezer with both a precise gripping action and the flexibility to suit a wide range of applications.

Features of the xyztec USB Tweezers

The gripping jaws (Tweezers or tips) are driven by a built‐in 3‐phase brushless micro drive to accurately open or close and the jaw actuators incorporate a strain gauge to precisely measure and control the grip force. There is a choice of two types of motor, standard force or high force, refer to the specification for the performance details. The combination of positional and force control provides programmable control of all the gripping functions.

• The gripping force is known from the inbuilt calibrated force sensor. A grip force can be programmed and is then maintained throughout the test via force control loop software.
• Similarly the position of the jaws is known and controlled via the actuating micro motor. This enables programmable control of the closing and opening positions.
• In the same way the closing and opening speed can also be programmed. Closing speed can be very important in some applications. Closing too fast can cause cracks to form in the bond due to the gripping action which are avoidable if the jaws close slowly.
• The tweezers are fitted to a standard pull sensor which provides the pull force data for the test. This sensor can also be used to sense when the tips of the jaws touch the sample and can also be used to land with a programmable force.
• Once contact with the sample has been detected. There is an option to raise the jaws to a programmable height above the contact position prior to closing the jaws to grip the sample.
• There are a standard range of jaws to suit many different applications, for example Gold wire pull or Aluminium ribbon peel. Custom designs for less common or new applications are also possible.
• The jaws themselves are Quick Release and can be changed in a matter of seconds. This is invaluable when a number of applications require different jaws designs.
• The Tweezer come complete with an integral illumination system of high intensity L.E.D.’s.
• The power and control of the tweezers is supplied by one USB connection to the machine computer.
• The USB tweezers is a stand‐alone device and can be used with any PC.

Specifications