iNEMI project evaluates BFR-free PCB materials
iNEMI project evaluates
BFR-free PCB materials
by Stephen Tisdale and Gary B. Long, Intel Corporation; Roger Krabbenhoft, IBM Corporation; Kostas Papath-
omas, Ph.D., Endicott Interconnect; and Terry Fischer, Hitachi Chemical
Several leading electronics companies predict their performance through the vari-
The electronics industry is under have publicly stated their intent to remove ous processes, although this was not always
pressure to eliminate bromi-
brominated and/or halogenated flame re- achieved. Materials that passed the basic
nated flame retardants (BFRs)
tardants from some or all of their products. material property requirements entered a
that were once widely used in
Alternative non-halogenated material sys- second phase—building of a test vehicle—
electronics housings and cases
tems are being developed and introduced to evaluate other material properties such
and are still used extensively
into products, typically using nitrogen or as processability, drilling, hole cleaning,
in printed circuit boards. The
phosphorus-based compounds, or a combi- plating, dimensional stability, assembly and
nation of both. However, the reliability of reliability performance.
iNEMI BFR-Free PCB Project
many alternative flame retardants has not
investigated claims by many
been fully qualified at the assembly level. Prepreg and laminate characterization
early adopters that the new
Industry needs to address whether sub- A Wabash enclosed-vacuum, two-opening,
class of halogen-free materi-
stitutes can meet the same technical and electric press was used to laminate all the
als performed better than the functionality requirements, whether they selected bromine-free materials for the vari-
status quo. The team evaluated
will decrease product safety or reliability, ous tests. Lamination conditions suggested
the electrical, mechanical and
and what the trade-offs may be. by the laminate suppliers were followed
reliability attributes of ‘halogen
The iNEMI BFR-Free PCB Project when available. Otherwise, a material was
reduced’ materials using known
tested several of the new halogen-free mate- laminated at a dwell temperature slightly
designs from IBM and Intel.
rials to determine performance. This article above its reported ultimate glass transition
This article discusses highlights
highlights results of those tests. temperature (Tg). The lamination pressure
was dependent upon the rheological prop-
of the results.
Material evaluations erties of the prepreg. For unclad sample
The adoption of halogen-free alternatives preparation, the copper was removed by
requires that the laminates have minimal etching in the cupric chloride bath set at
impact on the electrical, mechanical, 55oC. The samples were then dried in an
Keywords: Brominated Flame
electro-migration, chemical resistance, oven at 110˚C for one hour. The specific
Retardants, BFR-Free PCB Proj-
thermal, moisture absorption and rheologi- test methods followed for the evaluation
ect, Halogen-Free PWB cal properties. In addition, adhesion to of the bromine-free laminate materials
Laminate Materials copper, to the oxide treatment, and to properties were based on the IPC-TM-650
the laminate itself needs to be sufficient. standard, ASTM methods and internal
Processing and assembly performance of specifications of Endicott Interconnect
the laminate products must meet design (who performed the testing).
requirements.
The iNEMI team performed a series of Laminate electrical characteristic and
tests on 10 commercially available halogen- reflow compatibility evaluation
free PWB laminate materials (identified as This portion of the evaluation focused on
Materials A-K in this discussion), evaluat- the assessment of the frequency depen-
ing the electrical, thermal and physical dant dielectric constant and effective loss
properties of the new materials. This tangent as well as the propensity for the
testing provided sufficient information to laminates to survive elevated temperature
determine the relative robustness of each reflow environments. The 10 halogen-free
material with respect to basic properties, and control laminate materials were fabri-
both in the prepreg and laminate stages. cated into two specific test vehicle designs,
The comparison between the halogen-free designated SMASPP2z and HOP31B.
materials and the brominated control
was made by using only prepreg on 1080 Process simulation conditions
glass cloth type having resin content in The four-cell matrix of assembly process
the range of 50-70%. Ultimately the goal simulations consisted of the following con-
This paper was originally presented at SMTAI,
was to identify the materials with the best ditions, emulating mixed solder assembly
Orlando, Florida, USA, August 2008.
performance (based on testing) and to (MSA, 245˚C) and full Pb-free (260˚C)
10 – Global SMT & Packaging – March 2009 www.globalsmt.net
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