SMART Group launches “Lead-Free Process Defect Guide 2”
Bob Willis
SMART Group launches “Lead-
Free Process Defect Guide 2”
With the introduction of lead-free This issue of Global SMT & Packaging surface, cracking has been seen in the
assembly, engineers have experienced a features a selection of the type of epoxy to glass interfaces. Changes are
range of new process defects at each stage defects featured in the SMART Group often needed in the plating process
of manufacture. Some of the defects are guide and compiled by members of the to improve or promote adhesion and
completely new; others are re-occurrences SMART Group. Information on how eliminate hole wall pull-away. This type
of past problems. Fortunately some are to obtain the free guide is available of problem has been fairly uncommon
simply cosmetic and not liable to affect the at www.smartgroup.org prior to the introduction of lead-free
long-term reliability of products. laminates. Similar adhesion problems have
been experienced on surface mount pads
separating for the surface of the board.
Often some of the newer high Tg laminate
have a weaker copper foil adhesion to the
surface of the board. This is commonly
seen on area array packages where the
surface pad is particularly small.
Figure 1. Erosion of the copper core of a
The SMART Group Lead-Free Defect Guide 2
soldering iron tip.
is available as an A5 booklet so it can be easily
used in manufacture on the shop floor, making it
easily available for staff reference.
Soldering iron corrosion
During the early introduction of lead-free
SMART Group Lead-Free Defect solder, iron tip damage was very common
Guide 2 is now available FREE to assist due to the variability of the plating on
engineers in understanding process criteria some tips. It has also been caused by poor
and defect types. The A5 colour guide control and limited training of the impact
was first introduced in 2007 and has of the solder alloy and the reluctance of
now been updated and expanded over 45 staff to switch off irons when not being
pages. The guide now features a Lead-Free used. Figure 1 shows erosion of the copper
Process Checklist covering each stage of core due to lack of protective plating,
manufacture and can be used as an auditing which may have become damaged due to
tool. To aid engineers in monitoring their incorrect use of the tip.
process and benchmarking different
process steps, a guide to PPM monitoring Copper hole wall pullaway
has been included. The guide features Copper separating from the plated through
defects associated with components, hole can lead to problems. This should not
printed circuit boards, design, materials, occur, even with the elevated temperatures
assembly and rework. It also includes some of lead-free assembly. Many companies
of the problems that may be experienced have changed the laminate materials for
Figure 2. Copper separated from the plated
on field returns. lead-free assembly. With a harder epoxy
through hole.
4 – Global SMT & Packaging - August 2008 www.globalsmt.net
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