LAT  Electronics, Data Acquisition & Instrument Flight Software

  Subsystem Manager:  Gunther Haller

 

Important: EM2 test-stand hardware components are NOT compatible with hardware supplied for EM1 test-stands. Do not mix TEM/TEM-PS/Transition Card EM1 with EM2 hardware. Hardware for EM2 is marked "EM2" on the TEM, TEM-PS, VME Transition Card and LCB supplied.

Documents:

The documents are in the process of being transferred to the LAT-DOC system for official release, please retrieve them from LATDOC's.

Here are applicable document numbers and selected copies of the documents in the release cycle (use them with caution).

Note that we do not perform impedance/short/open/voltage measurements on all pins, but test functionality of the system. The "safe-to-mate" test is the responsibility of the sub-system.

Tracker:

EGSE-TKR TESTSTAND #2

LAT Quality Assurance

Performance & Safety Assurance LAT NCR Report

The following Nonconformance Report # 00197 was submitted on 10/01/04 16:39:32

 

Entered by Ludvik, Jeffrey - jsludvik@slac.stanford.edu

 

Found by:  Customer Complaint

Type of Nonconformance:  Minor

Discrepancy Level:  Non-Flight Hardware

Sub-System:  Electronics (ELEC)

Item Description:  EGSE TKR Teststand #2

Supplier: 

Location: 

Drawing/Rev #:   

Lot/Heat #: 

Serial #:  GLAT0679

Test Procedure/Rev #: 

 
Description of Nonconformance:  TEM/TPS from EGSE TKR Teststand #2 was received from INFN. Problem was described by INFN as unable to communicate on cable controller 2, GTCC 2. During safe-to-mate procedures they noticed low resistances. The TEM/TPS was inspected at SLAC and a problem with cable controller 2 was identified. The ASIC on GTCC 2 was measured and found Pin 23 shorted to 3.3V (25 Ohm). The ASIC was replaced, and resistance checked OK. The TEM/TPS unit also passed all performance testing. The ASIC was opened and some damage could be see on pin 23. There was a big discoloration on the pad around via connecting power (Metal2) to small island of power on Metal1 which is used by the signal. Problem possibly caused by high voltage or by a huge ESD event.
       

Disposition Area

Defect Code:  050 Electronic/Electrical

Disposition:  Rework 
(Valid  dispositions:  Rework, Repair, Use-as-is, Reclassify, Return to Vendor, Scrap, or Documentation Change)

Disposition Instructions:  The TEM/TPS unit was electrically tested at SLAC and a problem with cable controller 2 was identified. The ASIC on TEM board GTCC 2 was measured and Pin 23 found shorted to 3.3V (25 Ohm). The ASIC GTCC 2 was replaced, and resistance checked to be greater than 1 Kohm. The TEM/TPS unit also passed all electrical performance testing.

The TEM/TPS unit will be shipped back to INFN.

The defective ASIC GTCC 2 was sent to Accurel Systems for decapping. Damage was observed on pad 23 inside die. There was a big discoloration on the pad around via connecting power (Metal 2) to small island of power on Metal 1 which was used by the signal. Problem suspected caused by high voltage or a ESD event.

NCR closure approved by Y.C. Liew, LAT Quality Engineering, and David Nelson, LAT DAQ Engineering (e-mails on file).

Root Cause:  Most likely caused by shorting high voltage around 150 V while doing stray voltage test or some other improper executed safe-to-mate procedure. It could cause by ESD event during handling.

Action taken to Preclude Recurrence of Discrepancy:  All safe-to-mate testing procedure should protect pins from shorting to other pins.
Always wear an ESD wrist strap while working on the unit.