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Adapters Resolve RoHS-Compliant Soldering Problems
By William Sinclair, Aries Electronics Inc.
The Restriction of Hazardous Substances
Directive—frequently abbreviated as RoHS—was adopted in February 2003 by
the European Union and went into effect July 1, 2006. The directive
restricts the use of six different substances (lead, mercury, cadmium,
hexavalent chromium, polybrominated biphenyls, and polybrominated
diphenyl ether), but is generally referred to as the “lead-free
directive.”
This directive has resulted in unintended consequences for electronic
equipment manufacturers. Many electronic components have historically
been terminated in pins that are plated with a tin/lead composition, or
in the case of BGA balls, are actually made out of tin/lead. These
components are soldered to printed circuit boards (PCBs), which are used
in all kinds of electronic equipment, from toys and computers to
military devices.
One of the original reasons for including lead in the pin plating
compound is that the addition of lead greatly reduces the temperature
required to solder the electronic component to the PCB. For example, the
typical temperature for soldering tin/lead-plated components is around
220°C, while no-lead finishes, such as matte tin, can require a
temperature of 260°C or more for proper soldering.
The addition of lead also prevents the tin in the plating from flaking,
as well as the growth of tin whiskers, which can cause electrical
shorting problems in many applications, including but not limited to,
the military.
Because of the RoHS directive, many PCBs are now completely converted to
RoHS compliancy, while many others are still manufactured in the “old
way.” These differences can cause some significant headaches. For
example, if a design is set up for the “old way” and uses a soldering
temperature of 220°C, but one of the components is now only available in
RoHS-compliant form (meaning this device requires 260°C in order to be
soldered properly), the non-RoHS compliant PCB material and components
can burn or be damaged at the temperature required for the RoHS-compliant
component to be properly soldered.
One solution to this dilemma is lead-free BGA-to-tin/lead BGA adapters.
For example, Aries Electronics enables its customers to send RoHS-compliant
BGA devices back to the factory, and through a proprietary production
process, the high-temperature RoHS device is installed onto a
high-temperature PC board. Standard tin/lead solder balls are then
attached to the bottom of the adapter board, which the end user mounts
to its PCB using standard low-temperature assembly processes. These
types of adapters are helping to solve the solder joint reliability
problems that occur when the lower reflow temperatures cause the
incomplete reflow of the lead-free solder balls, while avoiding damage
to the PCB and other components on the board.
Figure
1–Aries’ BGA-to-BGA adapters resolve soldering problems that have arisen
as the RoHS-directive has been implemented.
Because of the widespread effects of RoHS-compliance,
this type of solution is ideal for a wide range of applications,
especially for the military, where there are great concerns about the
detrimental effects of tin whiskers and other valid reasons for not
respinning boards. By using these BGA-to-BGA adapters, many of the
typical soldering mismatch problems caused by RoHS compliancy can now be
resolved.
Solder joint reliability is just one of the problems associated with
RoHS, but an effective alternative has been found. This is a promising
trend showing that as the RoHS initiative gains ground, and as
manufacturers continue to develop new products within these constraints,
more solutions are bound to be discovered.
William
Sinclair is the president of Aries Electronics Inc., located in
Frenchtown, New Jersey, U.S.A. For more information on Aries’
products, go to
www.arieselec.com. |
