Measurements of the Printed Circuit Boards (PCB)

Simon Gonzalez (CSU Fresno)Despina Sampsonidou ( AUTH) and Claudio Savarese(Napoli Federico

II )

Precision of strips over large area

• 5 PCBs (0.6 x 2 m2) PCBs from ELTOS at CERN.• Measurements to be taken

– position of fiducial marks.– Strip pitch at different positions.

SideA

SideB

Instrument for fiducial measurements

• Traveling Microscope– Microscope that travels on tracks above a table– Digital readout– Measurements can be taken down to 0.01mm (10 μm)– Used on PCB2 and PCB3

Fiducial mark Copper strip

Fiducial results PCB2 – (B)

1 3 5 7 9 11 13 15 17 1924

24.2

24.4

24.6

24.8

25

25.2

25.4

25.6

25.8

26

f(x) = − 0.000253400143163902 x + 24.8755118110236

Distance from Fiducial to Strip

Position

Dis

tanc

e (m

m)

0 2 4 6 8 10 12 14 16 18 2099

99.2

99.4

99.6

99.8

100

100.2

100.4

100.6

100.8

101

f(x) = 0.00152631578947372 x + 99.9526315789474

Fiducial to Fiducial

Dis

tanc

e (m

m)

Position

Results for Fiducial reading

• PCB2 – average fiducial to strip reading of 24.87mm and fiducial to fiducial

reading of 99.97mm for side B.– average fiducial to strip reading of 24.88mm and fiducial to fiducial

reading of 99.97mm for side A.– Average length from strip A edge to strip B edge 500.28mm

• PCB3– average fiducial to strip reading of 24.89mm and fiducial to fiducial

reading of 99.98mm for side B.– average fiducial to strip reading of 24.88mm and fiducial to fiducial

reading of 99.99mm for side A.– Average length from strip A edge to strip B edge 500.33mm

Instrument for Strip pitch

• NA62 laser interferometer– Computer controlled laser that can take reading down to a

nanometer.

laser

Full Scan of PCB1

Full Scan 1

Full Scan 2

Full Scan 3

Finding the pitch

• What is pitch? • Small region analysis of the full data set.

-519.6 -519.4 -519.2 -519 -518.8 -518.6 -518.431.5

31.52

31.54

31.56

31.58

31.6

31.62

31.64

31.66

31.68

31.7

pitch

pitch

Current results Scan 1 Other “big” peaks → multiples of 400μm Other “small” peaks → multiples of 200μm Misidentified local maxima

Current results Scan 2

Gaussian

measurements

Problems

• Some bad fiducial marks/copper strips• Laser would move along the vertical after being set

Conclusion

• The boards are close to uniform with at most a 10μm to 50μm difference.

• Short analyses are promising a pitch of 400μm• About 1250 copper Strips within the 500mm

width of the board.• Work still needs to be done on the remaining

boards and analyses of the full data set need to be completed.