Status of Al-FPC development for IB

A. Di Mauro, A. Junique, P. RiedlerITS-MFT mini-week 11.03.2014

ITS-MFT mini-week - Al-FPC - A. Di Mauro 2

Updated layout

11/03/2014

AGND DGND

AVDD DVDD

3.5 mm 100 µm 100 µm

75 µm POLYIMIDE

25 µm ALUMINIUM

25 µm ALUMINIUM

~ 10 µm SOLDER MASK

~ 10 µm SOLDER MASK

4 mm

4 mm

11 mm

Changes wrt TDR version:• Polyimide thickness -> 75 mm

• ~ 90 W diff. impedance (estimated using Apical NP dielectric constant)

• Deeper holes (150 mm) better for laser soldering

• Larger holes 220 mm, better for laser soldering

• Solder mask coverlay, applied by spraying, all gaps are filled avoiding air bubbles formation (observed in PI coverlays).

AVDD

DVDD

DGND

AGND

High-speed differential lines

MLVDS differential lines

Signals connections

1

1

2

UEC5 connector

(contacts layout not yet implemented)

15 mm

to be determined

Extension for connection to service cables

Al-FPC

on service cable

AVDD

DVDD

2

Power connections Solder connections

Flex extension

AVDD & DVDD

AGND & DGND

15 m

m

Extension for connection to services

EoC raw and FPC width

11/03/20146

ITS-MFT mini-week - Al-FPC - A. Di Mauro

1.25

0.20.10.10.10.10.2

0.15

0.10.10.1

FPC edge

Differential lines

chip edge

0.55 (distance of EoC pad axis to chip edge)

0.7 (FPC extra width)

FPC padcommon distribution of DCTRL and DCLK

OK for integration!

ITS-MFT mini-week - Al-FPC - A. Di Mauro

Al-FPC production procedure

Main steps of procedure developed at CERN for STAR flex production (@ LERMPS (F)) :

1) Preparation of polyimide (Apical NP) substrate:– Thermal cycle (12 h at 180 oC) to induce max shrinking (new, under test)– Holes drilling by laser– Sand-blasting + outgassing

2) Deposition of Al layer (25 mm) (performed by DEPHIS (F), FHR (DE)):– Plasma cleaning– Pump down to 10-5 mbar– Cr film coating– Al sputtering (~ 10 h, in several steps to avoid overheating)

3) Chemical etching @ CERN (Laser etching tests by Swiss Micro Laser)4) Coverlay (solder mask) + Ni/Au @ CERN

711/03/2014

ITS-MFT mini-week - Al-FPC - A. Di Mauro 8

Summary of production tests

Supplier/sample date

comments

FHR/ 15 and 25 mm Oct 2013

Presence of small fibres embedded in the Al, small metallic bubbles on the surface, presence of black layer under the Al film, chemical etching was tried on 15 mm Al and didn’t work (material too dense) . After that: CERN recipe transferred to FHR

11/03/2014

ITS-MFT mini-week - Al-FPC - A. Di Mauro 9

FHR samples #1

11/03/2014

ITS-MFT mini-week - Al-FPC - A. Di Mauro 10

Summary of production tests

Supplier/sample date

comments

FHR/ 15 and 25 mm Oct 2013

Presence of small fibres embedded in the Al, small metallic bubbles on the surface, presence of black layer under the Al film, chemical etching was tried on 15 mm Al and didn’t work (material too dense) . After that: CERN recipe transferred to FHR

DEPHIS/ 15 and 25 mm Dec 2013

Al aspect not perfect, chemical etching ~OK, solder mask coverlay ~OK, Ni/Au deposition didn’t work (zincate attached and dissolved Al under the coverlay). Reasons: DEPHIS didn’t copy exactly the procedure from LERMPS (polarisation of PI foil during coating, …)

11/03/2014

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DEPHIS samples

11/03/2014

After etching, w/o coverlay

with coverlay

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Summary of production tests

Supplier/sample date

comments

FHR/ 15 and 25 mm Oct 2013

Presence of small fibres embedded in the Al, small metallic bubbles on the surface, presence of black layer under the Al film, chemical etching was tried on 15 mm Al and didn’t work (material too dense) . After that: CERN recipe transferred to FHR

DEPHIS/ 15 and 25 mm Dec 2013

Al aspect not perfect, chemical etching ~OK, solder mask coverlay ~OK, Ni/Au deposition didn’t work (zincate attached and dissolved Al under the coverlay. Reasons: DEPHIS didn’t copy exactly the procedure from LERMPS (polarisation of PI foil during coating, …)

FHR/ 15 and 25 mm Jan 2014

15 mm done on PI prepared at CERN, 25 mm done on PI prepared by FHR; Al aspect improved, however when testing with zincate Al reacted and lost adherence to PI. Etching was not tried.

11/03/2014

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FHR samples #2

11/03/2014

reaction to zincate

After Ni/Au: easy peel-off of Al, impossible to use for FPC pads !

ITS-MFT mini-week - Al-FPC - A. Di Mauro 14

Summary of production tests

Supplier/ date commentsFHR/ 15 and 25 mm Oct 2013

Presence of small fibres embedded in the Al, small metallic bubbles on the surface, presence of black layer under the Al film, chemical etching was tried on 15 mm Al and didn’t work (material too dense) . After that: CERN recipe transferred to FHR

DEPHIS/ 15 and 25 mm Dec 2013

Al aspect not perfect, chemical etching ~OK, solder mask coverlay ~OK, Ni/Au deposition didn’t work (zincate attached and dissolved Al under the coverlay. Reasons: DEPHIS didn’t copy exactly the procedure from LERMPS (polarisation of PI foil during coating, …)

FHR/ 15 and 25 mm Jan 2014

15 mm done on PI prepared at CERN, 25 mm done on PI prepared by FHR; Al aspect improved, however when testing with zincate Al reacted and lost adherence to PI. Etching was not tried.

LERMPS/ 25 mmFeb 2014

Zincate test OK, 6 FPC under processing

DEPHIS/ 25 mmFeb 2014

Zincate test OK on small sample, 15 FPC production just launched

11/03/2014

ITS-MFT mini-week - Al-FPC - A. Di Mauro

Laser etching testsUsing sample from FHR (not compatible with chemical etching!)

1511/03/2014

IR laser UV laser

Traces section not yet optimal (trapezoidal), further tests ongoing

ITS-MFT mini-week - Al-FPC - A. Di Mauro 16

Metrology checks- Polyimide shrinking on first exposure to high T: APICAL NP -> 0.04%

@150 oC for 0.5 h, 0.08% @ 200 oC for 2 h- Al-FPC production requires various thermal cycles:

- Outgassing: 180 oC - Al sputtering : 90-130 oC- Image transfer: 80 oC- Solder mask: 180 oC

- Metrology check to measure induced “shrinking”: distance between first and last contact along trace lines (nominal 268.8)

11/03/2014

ITS-MFT mini-week - Al-FPC - A. Di Mauro 17

Metrology checks

• avg shrinking = 0.49 (~ 0.2 %) (should be corrected by initial thermal stabilization process)

• st. dev. = 0.07 (statistics too small)11/03/2014

sample stage results

DEPHIS before solder mask

5 lines of same FPC: 268.562, 268.575, 268.545, 268.565, 268.528AVG= 268.56, STDEV=0.019

FHR before etching

5 lines of same FPC: 268.405, 268.396, 268.379, 268.366, 268.384AVG= 268.39, STDEV=0.015

DEPHIS before Ni/Au

2 lines of 5 different FPCs:- 268.387 268.357 - 268.238 268.279- 268.345 268.368- 268.228 268.246- 268.300 268.318AVG 268.3 268.32STDEV 0.07 0.052

ITS-MFT mini-week - Al-FPC - A. Di Mauro 18

Eye diagram

11/03/2014

• FPC in Cu, 50 mm polyimide ~ 90 W impedance (similar to Al FPC with 75 mm polyimide)

• 1.5 Gbit/s

(by M. Keil and A. Junique)

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Next steps

• Validation of chemical etching on LERMPS and DEPHIS FPCs, 6 + 15 prototypes in production

• Systematic dimensional control of FPC on all new production from DEPHIS, validate thermal stabilisation; if needed, try compensation of shrinking by modified hole positions in layout

• Finalize tests with laser etching and get a quotation from Swiss Micro Laser

• Launch pre-series production for IB full prototype

11/03/2014