ral instrumentation departmentviraj perera generic test module & bgas similar architecture to...
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RAL Instrumentation Department Viraj Perera
Generic Test Module & BGAs
• Similar architecture to DSS with Virtex FPGAs
RAL Instrumentation Department Viraj 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 Department Viraj 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 Department Viraj Perera
ERSASCOPE
• Visual inspection after:– Assembly– Re-work
Optical Instrument
RAL Instrumentation Department Viraj Perera
ERSASCOPE Visual Inspection -Typical BGA Problems Uncovered
• Database with typical problems and solutions
immediately available to the operator
RAL Instrumentation Department Viraj 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 Department Viraj 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!