Resolution of solder voids in pin-in-hole product
Resolution of solder voids
in pin-in-hole product
by Condia Yu, Eddie W. W. Tang, Jack To & Ka Wai Chan, Elec & Eltek, Hong Kong and Guangzhou, and
Brian Carlson, Rick Chen, PS Hou, Phil Isaacs, Eddie Kobeda, Sunil Nigam, Jeffrey Taylor & Kaspar Tsang
IBM Raleigh, NC, Rochester, MN and IBM China.
introduction
and more importantly reliable product that
What happens when a defect
Recent trends toward higher performance
does not degrade within a customer applica-
appears that is new, unique and increased densities in the electronics in-
tion. Optimization of process variables can
and different enough from dustry continue to place challenges on board
reduce the effects of known defects most
the typical defect that it is
and system manufacturers that integrate
prevalent in wave-soldered boards, namely
not readily apparent what
components and sub-systems, respectively. In
the occurrence of voids and blowholes in
caused the defect and wheth-
the printed circuit board (PCB) industry in
solder joints.
er it was caused during the
particular, the contradiction between high
This study reports the results of several
printed circuit board manu-
volume manufacturing and successful fab-
experiments that were designed to evaluate
facturing process, during the
rication of more complex circuitry requires
the conditions under which a particular
a continuous focus on controlling process
assembly process or, in fact,
solder void condition was created. Through
variability. This is especially true for those
by an interaction between
this series of experiments it was discovered
PCB suppliers that rely on multiple factory
that the permanganate desmear process
the two processes?
locations to fulfill customer requirements.
and, more specifically, the chemical controls
A unique plated-through- Ideally, the replication of identical processes
within this PCB manufacturing process
hole solder void which did from one factory to another provides the
step were the key driver for this thermally-
not meet IPC Class II
most efficient solution for a supplier as a
sensitive solder void problem.
printed circuit board work-
member of a complex supply chain.
manship requirements as per
As the industry adapts to ever-increasing
problem definition
IPC A610, Acceptability
demands for board real estate, resulting in
In July 2007 multiple IBM CMs reported
of Electronic Assemblies,
the need for more aggressive component
a solder void condition on several PCB
occurred on a large number
placement and a larger number of solder
part numbers. This solder void condition
joints, original equipment manufacturers
of assemblies
1
. There are sev-
was localized or most prevalent in DDR2
must remain vigilant in their approach to-
memory DIMM connector solder joints
eral questions which immedi-
ward quality assurance. For plated-through-
which happened to include the highest den-
ately arise: What caused the
hole (PTH) boards with high solder joint
sity of pin-thru-hole solder joints in the card
defect? Is the product accept- density, where wave solder processing is the
assembly (Figure 1). The solder void condi-
able for customer shipment? method of choice in the contract manufac-
tion was only present on PCBs from one of
Can the defective product be
turing (CM) environment, an understanding
several PCB suppliers and, more specifically,
reworked? Is this a seasonal
of risk sites and defect generation mecha-
from one of two factories in use by that
defect (e.g. laminate voids
nisms is critical to maintaining high yields,
PCB supplier. Oblique 2-D x-ray inspection
caused by high levels of
moisture in the laminate) or
has a variable in the process
shifted? A team of engineers
from multiple companies
worked together to answer
these questions.
Keywords: Solder, Voids,
Pin-Thru-Hole, Blowholes
This paper was originally presented
at PanPac 2009.
Figure 1. DIMM connector area on PCBA.
20 – Global SMT & Packaging – February 2009 www.globalsmt.net
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