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Many articles on interconnects discuss
bleeding edge new technologies,
new products, or provide guidelines
on optimizing system performance.
Having said that, standard pitch
(2.54, 2.00, or 1.27 mm centerline)
board-to-board interconnects are still
huge sellers and ubiquitous in the
electronics industry.
These two-piece connectors are not
as sexy as using ultra-high-density
interconnects with PAM4 to achieve
56 Gbps serial channels, but they
look mighty appealing if your job is to
identify and design-in reliable board-
to-board interconnect systems.
There are several design factors
that determine the success of the
interconnect system. Two of the
most important considerations are
selecting the right contact, and
selecting the right plating for that
contact.
Selecting the right contact helps
ensure your interconnect system will
meet the standards it is supposed
to meet – whether it is a high-
cycle application, or high shock and
vibration, or an interconnect that is
going to see very little stress in its
life.
The following is a basic overview of
contact design considerations:
CONTACT BASE METAL:
Three commonly used contact base
metals include phosphor bronze
(PhBr), beryllium copper (BeCu), and
brass. Brass has a tensile strength of
69 MPa - 434 MPa (Mega Pascal, unit
of pressure and tensile strength).
Compare this to Phosphor Bronze
with 131 MPa - 552 MPa, and BeCu
with 965 MPa - 1205 MPa.
Obviously, in industrial, high-risk,
hostile-environment applications, a
greater yield/tensile strength would
be desired, and in other applications
a more cost effective option would be
appropriate. Brass is generally only
recommended for simple, low-cycle
applications. While not as conductive
as brass, phosphor bronze boasts a
higher tensile strength. For the best
of both worlds, beryllium copper not
only offers the highest strength of the
three, but its conduction is close to
that of copper, making it well-suited
for strong, reliable connections.
CONTACT DESIGN BY END-
APPLICATION:
High reliability, high cycle contacts
are usually made of beryllium copper.
BeCu provides a strong combination of
mechanical and electrical properties
for high reliability interconnections.
High reliability contact systems
frequently have multiple points
Considerations In Selecting The Right Contact
For Your Interconnect System
Danny Boesing, Samtec, Inc.
56 l New-Tech Magazine Europe