ToF-SIMS analysis of glass fiber cloths for PCB manufacturing - IBM

ToF-SIMS analysis of glass fiber cloths 

for PCB manufacturing 

PCB Symposium Raleigh 2011 

Dylan Boday 1 , Michael Haag 2 , Joe Kuczynski 3 , Markus Schmidt 2 , Michael Wahl 4 , Johannes Windeln 2 

1 IBM Systems & Technology Group, 9000 S Rita Rd, Tucson AZ 85744-0002, dboday@us.ibm.com 

2 IBM Deutschland MBS GmbH, Hechtsheimer Str. 2, D-55131 Mainz, mhaag@de.ibm.com 

3 IBM Systems & Technology Group, 3605 Hwy 52 N, Rochester MN 55901-1407, kuczynsk@us.ibm.com 

4 IFOS GmbH, Trippstadter Straße 120, D-67663 Kaiserslautern, wahl@ifos.uni-kl.de

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 2

PCB structure 

prepregs 

cores 

copper lines 

prepregs: glass fiber cloth pre-impregnated with resin matrix 


heat, pressure 

heat, pressure 

pictures source: www.lpkf.de 

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...) 

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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 4

process steps critical with regard to Silanation: 

- starch size required for yarn processing 

- pyrolytic de-sizing (thorough?) 

- Silanation process 

application of starch sizing 

glass cloth conditioning 

pyrolytic de-sizing 

source: JPS Composite Materials 


(wet) application of Silanes 

11/11/11 5


motivation for ToF-SIMS analysis 

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! 

Thermal cracks: 

pictures source: Dynamic Details Inc. 

SEM micrograph: IBM 

CAF: Copper Anodic Filament 

11/11/11 6


motivation for ToF-SIMS analysis 

TGA and SEM/EDX results of analysed glass cloth 

indicate presence of undesired material 

expected weight loss < 0.1%! 

TGA analysis and SEM micrographs: IBM 

organic debris 

11/11/11 7

ToF-SIMS 

Time-of-Flight Secondary Ion Mass Spectrometry 

(Sample) 


extractor accelerates secondary ions to: 

E = q ⋅ U 

mass dispersion via ion flight time: 

v = 

⇒ 

t 

= 

2E 

m 

s 

v 

= 

= s ⋅ 

2q 

⋅ U 

m 

m 

2q 

⋅ U 

11/11/11 8

analytical setup 

Method: ToF-SIMS static and dynamic mode 

Tool: ION-TOF IV at , Germany 


Primary ions: 25keV Bi 3 + (clusters to promote molecular secondary ions) 

Samples: various samples of glass cloth – 

supposedly de-sized and coated with coupling agent 

sample 

# 

1 

2 

3 

4 

5 

6 

supplier 

A 

B 

C 

C 

C 

C 

cloth 

2116 

1080 

1080 

2113 

0106 

2116 

11/11/11 9

ToF-SIMS - static mode 

raw spectra 

significant differences especially in the hi-mass region 


#6 #6 

#6 

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ToF-SIMS - dynamic mode 

dynamic mode to distinguish between signals from 

surface coverage and bulk material 

glass bulk 

surface coverage 

sputter 

removal 

sputter 

removal 


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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 common 

appearance and behaviour 

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

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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 removal 

of surface layer: 

11/11/11 13


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? 



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group C (homogeneous organics) 

� laterally homogeneous signal 

� mainly hydrocarbons (C 7 H 7 , C 9 H 7 , C 9 H 9 , C 10 H 8 ) 

� phosphate component 



� 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) 



� surface coverage 

coupling agent or residues from sizing? 



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ToF-SIMS – second run 

Method: ToF-SIMS static and dynamic mode 

Tool: ION-TOF IV at , Germany 


Primary ions: 25keV Bi 3 + (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 

11/11/11 17

Glass cloth 

analyses 

first results 


NO SiCH 3 O + as reported by Norrmann et al (J. Mass Spectrom. 2002, 37, 695-708) 

NO other SiC complexes 

signal 

1,0E+05 

1,0E+04 

1,0E+03 

1,0E+02 

1,0E+01 

CH_3+ 

potentially Silane related: C x H y + and Cx H y O + 

but no change after heat and UV ozone treatment! 

C_2H_3+ 

C_2H_5+ 

C_3H_5+ 

C_3H_7+ 

C_4H_7+ 

C_4H_9+ 

C_5H_7+ 

C_5H_9+ 

element / fragment 

heat treated 

UV ozone 

as received 

C_2H_3O+ 

C_3H_3O+ 

C_3H_5O+ 

11/11/11 18

Glass pellet 

analyses 

first results 

signal 

1,0E+06 

1,0E+04 

1,0E+02 

1,0E+00 


potentially Silane related species C x H y + and Cx H y O + 

also present on bulk reference sample! 

��adsorbates from the ambient 

C_2H_3+ 

C_2H_5+ 

C_3H_5+ 

C_3H_7+ 

C_4H_7+ 

C_4H_9+ 

C_5H_7+ 

C_5H_9+ 

element/fragment 

fracture surface 

sputter cleaned 

as received 

C_2H_3O+ 

C_3H_3O+ 

C_3H_5O+ 

11/11/11 19

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 

next steps: 


- or only physisorbed instead of chemisorbed 

(due to insufficient fibre treatment) 

�work with supplier to improve Silanation process 

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

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

11/11/11 20

ToF-SIMS analysis of glass fiber cloths for PCB manufacturing - IBM

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