RAL Instrumentation DepartmentViraj Perera Generic Test Module & BGAs Similar architecture to DSS with Virtex FPGAs

RAL Instrumentation DepartmentViraj Perera Generic Test Module For ATLAS and CMS to test algorithms Delivered in December 2000 –Incorrect device supplied and fitted (XCV600 instead of XCV600E) –Component distributors took responsibility for the mistake –Re-worked twice without successes This took long time December 2000 to April 2001 –However one board was usable with some bits missing CMS is using it now to develop their firmware –Ordered two new boards and components PCBs arrived on time (26/5/2001) Waiting for the XCV1600E from Insight Should be available for use by June/July 2001

RAL Instrumentation DepartmentViraj Perera BGA Re-work Still investigating re-workability of BGAs –another company found with different re-work machine (infrared - see below) –Replaced fine pitch (0.5mm) TQFP (304 and 208 pin) devices successfully on a DSS previously thought not possible with a hot air tool Damage to pads, components around it coming off, etc –To gain experience, shall try the GTM with this method if there is no damage to the module after the previous two attempts

RAL Instrumentation DepartmentViraj Perera ERSASCOPE Visual inspection after: –Assembly –Re-work Optical Instrument

RAL Instrumentation DepartmentViraj Perera ERSASCOPE Visual Inspection - Typical BGA Problems Uncovered Database with typical problems and solutions immediately available to the operator

RAL Instrumentation DepartmentViraj Perera Problems with BGA assembly on 9U modules! The manufactures do not see any problems assembling BGAs (fine pitch (1 mm) or ‘standard’ (1.27 mm)) onto a 9U module. –Discussed the CPM ~30 BGA packages + –~ 20 Fine pitch BGAs –Few things to consider: PCB design (ground planes etc) to prevent bowing at re-flow PCB surface finish BGA outline (alignment markings) –Usually done with silk screen Tolerance from board-to-board may differ –Prefer corners marked with copper Avoid components (ICs) on back of the module

RAL Instrumentation DepartmentViraj Perera Problems with BGA assembly on 9U modules! Message: – With complex modules, over-the-wall approach could cause problems! Designers, PCB manufacturer and board assembler must work together and understand requirements for each stage!