Transcript Presentation_to_contagx

OB-FPC: FLEXIBLE PRINTED CIRCUITS FOR THE
ALICE TRACKER
Main Requirements.
The OB FPC must meet demanding requirements:
 Material: Low material budget

Electrical: impedance of differential lines @ 100W,
transmission control and readout signals up to 400Mb/s
without significant deterioration, minimal voltage drop
along power supply planes,

Dimensional: tight total dimension and holes/vias tolerance
Modules and stave assembly requires tight dimensional
constraints on vias/holes position, length, etc
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OB-FPC SPECIFICATIONS
FPC Dimensions: total 23 x 6 cm^2
Consists of:
main part (TAB+FOPC) + small independent components
STACK-UP SPECIFICATIONS
Substrate: Polyimide, 75 um
Metal: Cu, 18 um FINAL (top & bottom)
Coverlay: 20 um flex solder mask
Plating (not shown) on selected areas.
Aimed tolerance (impedance and mat.
budget): 10% separately for each layer.
Layer
Thickness (um)
Tolerance
Dielectric substrate
75
+-10 %
Copper (FINAL)
18
+- 10%
Coverlay (flex Solder mask) 20
+- 10%
STACK-UP SPECIFICATIONS
MATERIALS:
Chosen: Pyralux AP8535R by Dupont (double-sided, copper-clad
laminate, Cu thickness 18 um, polyimide core 75 um)
Brand: DUPONT
Name: Pyralux AP8535R
Dielectric constant: 3.4 @1 MHz (~3.4 @ ~500MHz)
Dissipation factor: 0.002@1 MHz (~0.004 @~500MHz )
Dielectric strength [kV/mil] 6-7
In-plane CTE: 25 ppm/C (T<220 C)
Operating temperature: 180 C max
Pyralux was chosen for its thermal, mechanical and electrical characteristics.
Alternative materials can be proposed if with similar characteristics
STACK-UP SPECIFICATIONS
• Starting thickness 18 um Cu (Pyralux) requires selective
metallization Thickness 18 um everywhere except around vias
Where metal thickness allowed up to 35um max.
Anyhow it must not exceed coverlay height.
Alternatively
 Starting with thinner Cu layers (or thinning 18 um Cu …) allows for
uniform Cu deposition
 What tolerances can be achieved?
Alternative solutions can be proposed by the firms given that the
final product complies with all the electrical, geometrical and
mechanical requirements.
SPECIFICATIONS FOR FPC PRODUCTION
Surface Finishing
The finishing must be chosen in order to guarantee a surface of
high quality for wire bonding
Tinplating
PB pads, lateral pads, bridges (see sec) should be tinplated for
easier later soldering.
DIMENSIONAL TOLERANCES
FPC contains: main circuit (OB-FPC + TAB section) + other structures
Dimensional tolerances are a crucial requirement for the assembly of the module
and later for the assembly of modules on staves.
This implies tight tolerances on positions of holes, vias, pads, length and width
TAB
Line of cut
OB-FPC
DIMENSIONAL TOLERANCES
Edge distance
TAB cut line
Referencepoint:
Dowel pin hole center
FPC edge
-Position of right FPC edge
-Position of all holes/vias centers
-Position of all pads
to be all defined with respect to the actual center of the central
dowel pin hole
OTHER SPECS
Numbers under review!
Tolerance for right FPC edge: +-25um.
Tolerance for upper and lower edges: +-50um.
Position and dimension of holes/vias (all shapes): +-50um
Lateral Pads (37+37): +-50 um
Other pads (PB, reference, sub/pw) : +- 50um
Dowel pin diameter: +-20um
Data lines
impedance requirement: 100W +- 5%
Implications on
 requirements on
- lines width 100 mm and distance 200 mm ± 5 μm
- dielectric, Cu and cover layer thickness and characteristics
Controlled impedance?
OTHER SPECS
• Flatness
Essential for proper assembling.
• Need for FPC identifier (DB)
•Ground (vias) and power (holes):
oblong holes (see fig.) : 1200 um (major axis) , 400 um (minor axis), with asymmetric crown
(crown width equal to 150um on one side, 100um on the other side).
•Signal holes:
oblong holes (see fig.) : 1600
um (major axis) , 400 um
(minor axis)
COMPONENTS MOUNTING
SMD components (88 of 0603 and/or 0402 type)
connectors (2) to be mounted on each FPC
PREPARATION OF SPECIFICATIONS FOR FPC PRODUCTION
Quality assurance
Several of our requirements difficult/impossible to be verified by companies
Asking for a minimal set of tests:
Firms are required to provide circuits tested for
- Isolation of lines
- Continuity of lines
- Flatness of FPC
- General optical inspection (Plating quality,…)
- cleanliness
- Proper connection of surface m. components, if applicable
All other requirements to be verified by us after delivery:
Full tests on pre-production (a preproduction should be required before
starting full pr.)
Systematic tests on all produced FPCs
Full tests on samples (batch validation)