| If Your
Device Under Test Has |
Your
Fixturing Should Have |
Discussion |
| Contacts that oxidize (such as
silver, tin, or nickle) |
Pins that can scrape or poke
through the oxide on the contacts. You'll find test block pins
may need to use spring-loaded contacts. |
When you use contacts that can
oxidize you'll find the fixturing connector must work harder to
scrape or poke through the (usually non-conductive) oxide. Your
fixturing pins need a higher contact pressure or a longer wiping
distance. This increased pressure or wiping distance causes your
fixturing connector to wear out sooner. You'll find the
connector on your device under test also wears out quicker.
Spring loaded pins can focus the contact force on
a tiny spot and break through the oxide without damaging the
contact. These pins tend to last longer than standard contacts
and the spring-loaded pins are usually replaceable. |
| Contacts with "gold flash" |
Connectors with gold plated
contacts; 15 to 30 micro-inches of gold plating works well. |
Gold flash is extremely thin. If
the gold flash on a contact wears away the contact's base metal
will be exposed. Usually this base metal will oxidize and create
a poor contact. If your fixturing contacts have a thick layer of
gold plating you'll reduce the wear on the gold flash contacts.
Often times a connector manufacturer will offer a few contact
plating options for a connector. Select the option with 15-30
micro-inches of gold plating. |
| Contacts with gold plating. |
Connectors with gold plated
contacts; 15 to 30 micro-inches of gold plating works well. |
Gold plating on both connectors
generally gives the best results. If the connector on your
device under test and the connector on your fixture both have
15-30 micro-inches of gold plating you'll find your fixturing
lasts thousands of cycles. |
| Pins |
Select sockets made with gold
plating over beryllium copper. |
Sockets wear out fast. They tend
to lose their elasticity and tension. Once the tension starts
dropping you'll begin having intermittent or high resistance
connections. Beryllium copper holds up well. It maintains its
tension and elasticity for more cycles than other metals. |
| Sockets |
Avoid stamped pins that have
sharp edges. Use beryllium copper pins when the pin diameter is
less than 0.025". |
You want to use pins that have properly
formed corners. Some stamped pins have a sharp metal flash on
the edge of the pin. This flash can cut or wear the socket. Poor
quality pins often damage the sockets.
As the pin diameter gets thinner you'll want
to select a stronger pin. Beryllium copper pins work well when
the pin diameter gets near 0.025". |
