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Quality Assurance
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Factory tests of printed circuit boards
Continuity and Isolation tests to verify that the boards match gerber
data. Done on all boards.
Verify that board dimensions and hole sizes meet specifications as
described in the drill drawings. Done on a randomly selected sample
of boards: at least 10% of each type of board.
Verify the impedance in all layers of the board. Done on a randomly selected
sample (10%) of each type of board.
Post-Assembly factory tests
Visual inspection of all boards
Verify alignment of pins on Summing boards and High Voltage boards
Post-Delivery tests at BNL
Summing Boards:
Dunk randomly selected sample in LN2 to ensure that boards are mechanically
sound.
Visual Inspection of all boards and ensure presence of connection to every pin.
Continuity and Isolation test at room temperature using a programmable
cable tester. We utilize a
Signature Touch1 Cable Tester with Graphical Touch Screen Control
for performing the test on ALL boards. The tester essentially performs
a two-point resistance measurement between two sets of inputs (typically
64-pin inputs but can be changed). Special cable harness have been made to
connect each board to the cable tester.
The tester is then programmed to learn a single board and the
tolerance for pass criteria are set. The tester provides an immediate
answer whether each board being tested has passed by comparing against
the reference board. Typical time for testing each board after initial
setup is 1-2 minutes. This procedure was successfully used in the
test of prototype summing boards.
Mother Boards:
Visual Inspection of all assembled boards.
A full test will be performed on a randomly selected sample: at least
10% of each type of board. The tests will include:
Impedance measurements, Signal and Calibration
Cross Talk measurement, Signal Uniformity across the entire board.
Each prototype mother board is tested at room temperature and LN2. The
tests involved performing
a precision 4-point resistance measurement between the calibration input
and the signal input and recording each resistor measurement.
For the prototype mother boards, the tests were performed manually. An
automated system is being designed for the final production. This involves
the use of the switching matrix controlled from a PC over a GPIB interface
to allow a full mother board to be tested without human intervention.
4-point resistance measurements will autotmatically be recorded in a database
and compared against preset tolerance. Note that such an extensive tests
also automatically tests the continuity and isolation between the signal
input and signal output on the mother board. It is necessary to make the
measurements of all boards at room temperature and LN2 to ensure that the
TCR falls within specifications.
We have performed extensive analysis of individual resistive networks to
determine whether they meet the required specifications. A
detailed description of tests and the results on prototypes
are available here.
High Voltage Boards:
Visual Inspection of all boards to ensure a presence of connection to
every pin.
Test of randomly selected boards in LN2 to ensure mechanical stability.
Apply up to 2kV at room temperature on ALL boards and ensure that current
drawn by the board is of the order of a few nA. Tests of prototype HV board
indicate average currents of 0.5nA at 2kV at room temperature.
Alignment (G10) Boards:
Visual Inspection of all boards.