tof-sims analysis of glass fiber cloths for pcb manufacturing · tof-sims analysis of glass fiber...

PCB Symposium Raleigh 2011

ToF-SIMS analysis of glass fiber clothsfor PCB manufacturing

Dylan Boday1, Michael Haag2, Joe Kuczynski3, Markus Schmidt2, Michael Wahl4, Johannes Windeln2

1 IBM Systems & Technology Group, 9000 S Rita Rd, Tucson AZ 85744-0002, [email protected] IBM Deutschland MBS GmbH, Hechtsheimer Str. 2, D-55131 Mainz, [email protected] IBM Systems & Technology Group, 3605 Hwy 52 N, Rochester MN 55901-1407, [email protected] IFOS GmbH, Trippstadter Straße 120, D-67663 Kaiserslautern, [email protected]


11/11/11 2

content

• PCB (Printed Circuit Board) structure

• glass cloth conditioning

• motivation for ToF-SIMS analysis

• analytical setup

• ToF-SIMS results

• summary and outlook


11/11/11 3

PCB structure

prepregs

cores

copper lines

heat, pressure

heat, pressure

prepregs: glass fiber cloth pre-impregnated with resin matrix

cores: cured glass cloth/resin composite with structured copper layer(s)

multi-functionality of composite (glass cloth, resin and optional filler)- mechanical properties (strength, CTE...)- dielectric properties (insulation, impedance...)

pictures source: www.lpkf.de


11/11/11 4

glass cloth conditioning

glass fibers pre-treated with Silanes for- improved surface wetting (contact angle reduction)- improved matrix adhesion (organofunctional group R to match matrix resin)


11/11/11 5

process steps critical with regard to Silanation:- starch size required for yarn processing- pyrolytic de-sizing (thorough?)- Silanation process

source: JPS Composite Materials(wet) application of Silanes

application of starch sizing

pyrolytic de-sizing

glass cloth conditioning


11/11/11 6

motivation for ToF-SIMS analysis

CAF: Copper Anodic FilamentThermal cracks:

pictures source: Dynamic Details Inc.

SEM micrograph: IBM

challenges for modern high performance boards- increasing # of copper layers (�40 and above)- decreasing line width and spacing (� 50µm and below)- RoHS (Pb-free solder; solder process + 20K, new resins)

�� known sporadic failures become epidemic!


11/11/11 7

motivation for ToF-SIMS analysis

TGA and SEM/EDX results of analysed glass clothindicate presence of undesired material

expected weight loss < 0.1%!

organic debris

TGA analysis and SEM micrographs: IBM


11/11/11 8

ToF-SIMS

Time-of-Flight Secondary Ion Mass Spectrometry

(Sample)

extractor accelerates secondary ions to:

mass dispersion via ion flight time:

UqE ⋅=

Uq2

ms

v

st

m

Uq2

m

E2v

⋅

⋅==⇒

⋅

==


11/11/11 9

analytical setup

Method: ToF-SIMS static and dynamic mode

Tool: ION-TOF IV at , Germany

Primary ions: 25keV Bi3+ (clusters to promote molecular secondary ions)

Samples: various samples of glass cloth –supposedly de-sized and coated with coupling agent

2116C6

0106C5

2113C4

1080C3

1080B2

2116A1#

clothsuppliersample


11/11/11 10

ToF-SIMS - static mode

raw spectra

significant differences especially in the hi-mass region

#6 #6#6


11/11/11 11

dynamic mode to distinguish between signals from

surface coverage and bulk material

surface coverage

glass bulk

sputter

removal

sputter

removal

ToF-SIMS - dynamic mode


11/11/11 12

ToF-SIMS – first results

� ToF-SIMS imaging capability(microscopic picture 300µmx300µm „in the light of an ion mass“)

� major signals assigned to one of 4 peak groups with commonappearance and behaviour

group A: group B: group C: group D:


11/11/11 13

ToF-SIMS – peak groups

group A (glass constituents)

� laterally homogeneous signal

� glass constituents (Li, B, Mg, Al, Si, Ca, Ti, Na, K)

� signal increased after sputter removal of surface layer (≈30nm)� confirms glass constituent

different:

� Na and K: signal increase after sputter on #7,signal decrease on #1 � sizing component?

after sputter removalof surface layer:


11/11/11 14


group B (inhomogeneity I)

� signal limited to prominent portions of single fibers

� Sulfate component

� signal decreased after sputter removal of surface layer (≈30nm) � confirms surface coverage

residues from sizing or just abrasion debris from plastic bag?



11/11/11 15


group C (homogeneous organics)

� laterally homogeneous signal

� mainly hydrocarbons (C7H7, C9H7, C9H9, C10H8)

� phosphate component

� signal decreased after sputter removal of surface layer (≈30nm) � surface coverage

coupling agent?



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group D (inhomogeneity II)

� signal confined to small areas on single fibers

� fragmentation pattern match: Erucamide (m=337)

� signal decreased after sputter removal of surface layer (≈30nm) � surface coverage

coupling agent or residues from sizing?



11/11/11 17

ToF-SIMS – second run

Method: ToF-SIMS static and dynamic mode

Tool: ION-TOF IV at , Germany

Primary ions: 25keV Bi3+ (clusters to promote molecular secondary ions)

Samples: 1. 2116 glass cloth w/ Silane treatment (supplier‘s claim)

- as received- heat cleaned (matching pyrolytic de-sizing)

- UV-ozone cleaned (details undisclosed)

2. pellet of glass raw material (as used to pull fibers for 2116)

analyzed as a reference- as receiced- on freshly fractured surface- on sputter cleaned surface


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first results

NO SiCH3O+ as reported by Norrmann et al (J. Mass Spectrom. 2002, 37, 695-708)

NO other SiC complexes

potentially Silane related: CxHy+ and CxHyO

+

but no change after heat and UV ozone treatment!

Glass cloth

analyses

1,0E+01

1,0E+02

1,0E+03

1,0E+04

1,0E+05

CH

_3

+

C_

2H

_3

+

C_

2H

_5

+

C_

3H

_5

+

C_

3H

_7

+

C_

4H

_7

+

C_

4H

_9

+

C_

5H

_7

+

C_

5H

_9

+

C_

2H

_3

O+

C_

3H

_3

O+

C_

3H

_5

O+

element / fragment

sig

na

l

heat treated

UV ozone

as received


11/11/11 19

first results

potentially Silane related species CxHy+ and CxHyO

+

also present on bulk reference sample!

��adsorbates from the ambient

Glass pellet

analyses

1,0E+00

1,0E+02

1,0E+04

1,0E+06

C_

2H

_3

+

C_

2H

_5

+

C_

3H

_5

+

C_

3H

_7

+

C_

4H

_7

+

C_

4H

_9

+

C_

5H

_7

+

C_

5H

_9

+

C_

2H

_3

O+

C_

3H

_3

O+

C_

3H

_5

O+

element/fragment

sig

na

l

fracture surface

sputter cleaned

as received


11/11/11 20

summary and outlook

new ToF-SIMS application in reverse engineering:

Silane treatment of glass fibre cloth

first results on supplier samples:

NO Silane related secondary ions detected

� functionalized surface not as desired- Silanes either not present

- or only physisorbed instead of chemisorbed(due to insufficient fibre treatment)

next steps:

�work with supplier to improve Silanation process

�Is “pad cratering” part of the same problem?

�Is this the time to involve „computational materials science“?

tof-sims analysis of glass fiber cloths for pcb manufacturing · tof-sims analysis of glass fiber...

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