iNEMI project evaluates BFR-free PCB materials
effective Df* microvia results
hF laminate resin content 1ghz Df 5ghz Df 10ghz Df 20ghz Df
Ist results (# passing 1000 cycles)
rich/Poor Material/ 40 mil 80 mil
Material A Rich, 66% N/A N/A N/A N/A
Supplier Code board board
(control) Poor, 55% N/A N/A N/A N/A
A (control) 13 11
Material B Rich, 70% 0.0189 0.0201 0.0203 0.0204
B 15 15
Poor, 53% 0.017 0.0184 0.019 0.019
C 15 15
Material C Rich, 73% 0.0182 0.0191 0.0192 0.0192
D 15 15
Poor, 53% 0.0144 0.0153 0.0159 0.0172
E 15 15
Material D Rich, 73% 0.0171 0.0182 0.0183 0.0187
F 11 4
Poor, 53% 0.0136 0.0151 0.016 0.0168
G 5 15
Material E Rich, 73% 0.0188 0.0201 0.0203 0.0209
H 15 15
Poor, 53% 0.0169 0.0183 0.0188 0.0195
I 9 3
Material F Rich, 73% 0.0196 0.0203 0.0206 0.021
J 15 10
Poor, 53% 0.0166 0.0173 0.0176 0.018
K 8 1
Material G Rich, 73% 0.0197 0.0207 0.0207 0.0207
Table 5. IST results for Microvia coupons.
Poor, 53% 0.0169 0.018 0.018 0.0189
conditions pointed out interlayer weakness
Material H Rich, 73% 0.0202 0.0206 0.02 0.0209
in some materials. Most of the materi-
Poor, 53% 0.0166 0.0177 0.018 0.0192 als exhibited relatively good adhesion to
Material I Rich, 70% 0.0213 0.0224 0.0217 0.0222
copper (Gould JTCS-1oz), with the best
adhesion being materials B, J and K, which
Poor, 51% 0.019 0.0205 0.0205 0.0214
exhibited >8lbs/in adhesion values
Material J Rich, 70% 0.0236 0.0253 0.0256 0.026
The thermal expansion coefficient
measurements for the various bromine-
Poor, 51% 0.0207 0.0225 0.0231 0.0237
free laminates, both below and above the
Material K Rich, 67% 0.0209 0.0216 0.021 0.0207 glass transition temperature, indicate that
the in-plane expansion is similar to the
Poor, 53% 0.0151 0.016 0.016 0.016
brominated materials, in the range of 17-22
** Effective Df: includes Cu skin effects
ppm/˚C. The out of plane data indicate
relatively lower values with an average of
Table 4. Effective loss tangent after bake/reflow.
around 45 ppm/˚C below Tg. The lower
out of plane expansion is due to the con-
applicability of this data to the product materials, thermal stability of these materi-
straining properties of the fillers used to
environment must consider the use of the als is increasingly important. Laminates
impart V0 rating.
pre-bake in this analysis, i.e. if pre-bakes may have to survive extended periods
The iNEMI project team recommends
are not employed in the product environ- of time at elevated temperature during
individual testing of any material for the
ment, the infusion of moisture during the processing. The time to delamination
specific application by the designer prior to
fabrication process may lead to different tests at 260˚C, 288˚C, and 300˚C, as
mass production.
results. The IST coupons need cross- detected by rapid fluctuations in the TMA
section analysis to draw any conclusions on expansion probe position, are regarded as
via performance, but there appears to be a good measure of the resistive thermal
references
differing performance levels among the HF properties of the laminates to withstand
1. Extraction of Er(f) and tan d(f) for
materials tested. high temperature assembly conditions. The
Printed Circuit Board Insulators Up
The bromine-free prepregs tested in bromine-free materials in general do not
to 30 GHz Using the Short Pulse
general appeared to be tack free and of show problematic results and are in line
Propagation Technique, A. Deutsch,
good quality. Although having significant with the brominated materials used by the
T.M. Winkel, G. Kopcsay, C. Surovic,
inorganic content, their minimum viscosi- electronics industry at the present.
B. Rubin, G. Katopis, B. Chamberlin,
ties indicated that there is sufficient flow The majority of the candidates showed
R. Krabbenhoft, IEEE Transactions
during lamination. In general, the flame a glass transition temperature in the range
On Advanced Packaging, Vol 28, No.
retardancy is achieved by the introduc- of 150˚C, as measured by the DSC middle
1, pp. 4 – 12, Feb 2005.
tion of a combination of inorganic fillers point method.
2. Humidity Dependent Loss in PCB
based on Si, Al, Mg and P containing Moisture absorption at room tem-
Substrates, G. Brist, P. Hamilton, J.
compounds. perature at 24 hours showed relatively low
Schrader, G. Barnes, Printed Circuit
With the advent of lead-free solder values, with a number of materials being
Design and Fab June 2007
technology pushing the limits of laminate below 0.20%. Exposure to hydrothermal
www.globalsmt.net Global SMT & Packaging – March 2009 – 15
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