Status of Al-FPC development for IB A. Di Mauro, A. Junique, P. Riedler ITS-MFT mini-week

Updated layout 11/03/2014ITS-MFT mini-week - Al-FPC - A. Di Mauro2 AGNDDGND AVDDDVDD 3.5 mm 100 µm 75 µm POLYIMIDE 25 µm ALUMINIUM ~ 10 µm SOLDER MASK 4 mm 11 mm Changes wrt TDR version: Polyimide thickness -> 75  m ~ 90  diff. impedance (estimated using Apical NP dielectric constant) Deeper holes (150  m) better for laser soldering Larger holes 220  m, better for laser soldering Solder mask coverlay, applied by spraying, all gaps are filled avoiding air bubbles formation (observed in PI coverlays).

High-speed differential lines MLVDS differential lines Signals connections 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 mm Extension for connection to services

EoC raw and FPC width 11/03/ ITS-MFT mini-week - Al-FPC - A. Di Mauro FPC edge Differential lines chip edge 0.55 (distance of EoC pad axis to chip edge) 0.7 (FPC extra width) FPC pad common distribution of DCTRL and DCLK OK for integration!

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 o C) to induce max shrinking (new, under test) – Holes drilling by laser – Sand-blasting + outgassing 2) Deposition of Al layer (25  m) (performed by DEPHIS (F), FHR (DE)): – Plasma cleaning – Pump down to mbar – Cr film coating – Al sputtering (~ 10 h, in several steps to avoid overheating) 3) Chemical CERN ( Laser etching tests by Swiss Micro Laser) 4) Coverlay (solder mask) + CERN 7 11/03/2014ITS-MFT mini-week - Al-FPC - A. Di Mauro

Summary of production tests Supplier/sample datecomments FHR/ 15 and 25  m 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  m Al and didn’t work (material too dense). After that: CERN recipe transferred to FHR 11/03/20148ITS-MFT mini-week - Al-FPC - A. Di Mauro

FHR samples #1 11/03/20149ITS-MFT mini-week - Al-FPC - A. Di Mauro

Summary of production tests Supplier/sample datecomments FHR/ 15 and 25  m 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  m Al and didn’t work (material too dense). After that: CERN recipe transferred to FHR DEPHIS/ 15 and 25  m 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, …) 11/03/201410ITS-MFT mini-week - Al-FPC - A. Di Mauro

DEPHIS samples 11/03/ After etching, w/o coverlay with coverlay ITS-MFT mini-week - Al-FPC - A. Di Mauro

Summary of production tests Supplier/sample datecomments FHR/ 15 and 25  m 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  m Al and didn’t work (material too dense). After that: CERN recipe transferred to FHR DEPHIS/ 15 and 25  m 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  m Jan  m done on PI prepared at CERN, 25  m 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. 11/03/201412ITS-MFT mini-week - Al-FPC - A. Di Mauro

FHR samples #2 11/03/ 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

Summary of production tests Supplier/ datecomments FHR/ 15 and 25  m 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  m Al and didn’t work (material too dense). After that: CERN recipe transferred to FHR DEPHIS/ 15 and 25  m 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  m Jan  m done on PI prepared at CERN, 25  m 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  m Feb 2014 Zincate test OK, 6 FPC under processing DEPHIS/ 25  m Feb 2014 Zincate test OK on small sample, 15 FPC production just launched 11/03/201414ITS-MFT mini-week - Al-FPC - A. Di Mauro

Laser etching tests Using sample from FHR (not compatible with chemical etching!) 15 11/03/2014ITS-MFT mini-week - Al-FPC - A. Di Mauro IR laserUV laser Traces section not yet optimal (trapezoidal), further tests ongoing

Metrology checks -Polyimide shrinking on first exposure to high T: APICAL NP -> o C for 0.5 h, 200 o C for 2 h -Al-FPC production requires various thermal cycles: -Outgassing: 180 o C -Al sputtering : o C -Image transfer: 80 o C -Solder mask: 180 o C -Metrology check to measure induced “shrinking”: distance between first and last contact along trace lines (nominal 268.8) 11/03/201416ITS-MFT mini-week - Al-FPC - A. Di Mauro

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/ samplestageresults DEPHISbefore solder mask 5 lines of same FPC: , , , , AVG= , STDEV=0.019 FHRbefore etching 5 lines of same FPC: , , , , AVG= , STDEV=0.015 DEPHISbefore Ni/Au 2 lines of 5 different FPCs: AVG STDEV ITS-MFT mini-week - Al-FPC - A. Di Mauro

Eye diagram 11/03/2014ITS-MFT mini-week - Al-FPC - A. Di Mauro18 FPC in Cu, 50  m polyimide ~ 90  impedance (similar to Al FPC with 75  m polyimide) 1.5 Gbit/s (by M. Keil and A. Junique)

Next steps Validation of chemical etching on LERMPS and DEPHIS FPCs, 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 11/03/201419ITS-MFT mini-week - Al-FPC - A. Di Mauro