UniBoard Review

Report
X-RAY Images of UniBoard
NEWAYS / FIX TRADE
+ TDR measurements
© ASTRON
1
Explanation
X-RAY image
BGA connection
PAD on layer 2
Via in flip-chip package
Outside solder ball
Inside solder on pad
Histogram plot,
dark is pink (more metal)
Board via 2-13
Micro via in pad
X-Ray machine
© ASTRON
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BGA U16-F2
 BN 2 pin AT23
 MBII A4
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 X-Ray angle 45DEG
 FN 2 –AT18
 MBII A13
© ASTRON
4
 FN 2 Memory
 MBII A13
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 FN 2 Memory
 MBII DQ42
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Conclusions
 Soldering O.K.
 Micro via not clear but seems O.K.
 Via at memory o.k. (measure from top to
module with multimeter)
 Still open two possibilities:
Bad micro via
Chip damaged
 Bad chip
 ESD (handling of board/chip during use or
manufacturing)
© ASTRON
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Next STEPS
 Remove chip
Measure connections between BGA-pad and
memory
 Replace with new chip
Suggestion: Replace only FN2 (two bad
connections)
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© ASTRON
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PCB
 2.4mm
 High TG
material
 FR408
366mm
340mm
© ASTRON
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© ASTRON
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REMOVE CHIP
 REPORT Sjouke:
Removing FN2 UniBoard
Astron-RP-xxx
 Conclusion:
No chip problem at AL17(DQ42) and AT18
(A13)
PCB open connection
© ASTRON
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FN2 DQ42
Layer 2: 0.7mm
Micro via Layer 1-2
buried via Layer 1-2
Layer 10: 32.8mm
Through hole via Layer 1-2
Layer 14: 2.4mm
Total Length: 35.9 mm
© ASTRON
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TDR measurements
Connection to
mem. test board
yellow reference
board
Cyan board with
open contact
Connection to pcb
Open end 
reflection + ∞
Wrong value ! With Er 4.8 length 35mm
© ASTRON
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Conclusion TDR
Zoomed in to end
 Length to open >
34mm  Through
hole via O.K.
 Resolution TDR >
10mm  not clear
micro or buried
via.
 Test @ FN3 same
result
© ASTRON
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