The PTH is, in effect, simply a card cage that holds some mix of Application Modules (5 x 6 inch Printed Circuit cards) and has the means to distribute their signals to and from the DUT (Device-Under-Test). It connects with the Tester Mainframe through cabling to a special, dedicated controller.

A typical setup involves mounting the PTH (18.5 x 17.5 x 8.5 inch) on a manipulator for either manual DUT insertion or docking with one of several commercially available handlers or wafer probers. The PTH weighs approximately fifty pounds. There are two knobs for adjusting the positioning of the PTH in relation to the manipulator mounting arm. These knobs are located adjacent to the mounting arm where it enters the PTH enclosure.

One knob, when loosened, allows the PTH enclosure to tilt approximately 5 degrees up or down with respect to the manipulator mounting arm. This is useful for planarization of the PTH when interfacing to a packaged device handler or wafer prober.

The other knob moves the pivot point of the manipulator mounting arm with respect to the PTH enclosure. When properly set, the PTH will be evenly balanced when the first knob is loosened. It should not be necessary to adjust this second knob once the PTH has been set up.

The functions of each Application Module are distributed to the DUT through an interface known as the Module Interface Board (MIB). All Application Modules connect to a single, 15 x 16 inch Module Interface Board through individual ZIF connectors.

Actually, the distribution of Application Module functions to the DUT involves one more unit, the Swap Board, which is simply a carrier for the DUT socket (or handler contacts, etc.). The Swap Board mates with the Module Interface Board through some 600 spring contact pins (pogo pins).

The idea of the PTH is to have the functional equivalent of the Tester Mainframe "user-area" out at the Test Head, but not as part of a specific device Socket Adapter. Instead, the sensitive circuits required for a given application are on the PC cards (Application Modules) physically located close to the DUT (in the PTH card cage) and which can be interconnected under software control.

The PTH can be populated with a variety of Application Modules, perhaps multiple modules for heavily used functions and single modules for others. Only modules required for each specific application would actually be connected, under control of the application program, to the Module Interface Board and subsequently distributed to the DUT through its particular Swap Board. A different DUT might require a different mix of modules to be connected and most likely a different Swap Board. However, the Module Interface Board should remain the same.

The total number of functions that your applications must route through the spring contact pins can usually be accommodated by a single Module Interface Board. No exchange of the Module Interface Board from device family to device family would then be required. If that is not possible, then one Module Interface Board would be "wired" to carry the Application Module functions associated with a particular device family while another Module Interface Board would do the same for other device families. At any rate, the Application Module mix inside the PTH will typically remain the same regardless of the device family currently being tested.

Test solutions will be created by the mixing and matching of several "standard" Application Modules:

• Front-End measurement circuits – buffers, integrators, amplifiers, attenuators, etc.
• Switching relays – for switching local signals to various DUT pins
• Device "Family-specific" test circuits – control loops, inductive loads, etc.

A particular complement of these modules provides a "solution" for a given device family. Many different solutions can be provided within a single PTH, using different combinations of modules.

In some cases, special purpose Application Modules will be needed to provide the proper function mix. These modules can be obtained from the ATS Mixed- Signal Applications Engineering group (please contact ATS for details) or you can develop your own Application Modules following the procedures outlined in Chapter 3 of the PTH User's Manual.