Test Probe Information

Contents:
1. SMT Probes
2. Cyclo-Soldered Probes
3. High Current Probes
4. Custom Probes
5. Receptacles and the 5 receptacle styles.

Whether you are testing bare or loaded, conventional or SMT PCB's, you can maximize your testing efficiency by selecting the correct probe. Probes are manufactured in a combination of sizes (dimensional configurations), tip styles, and spring pressures to meet a variety of testing factors such as test pad geometry, component lead length, hole size, solder mask, and electrical current/resistance rating. In general, probes are divided into two groups - Bare Board (Short Stroke probes) and Loaded Board (Long Stroke probes). Short Stroke probes usually have a full plunger travel of .160 in. (4,06mm) or less while the longer stroke probe is typically .250 in. (6,35 mm).

MIXED TEST CENTERS
In some cases test centers vary on a PCB and you may need to mix probe sizes within a test fixture. This can be accomplished by selecting probes with a similar plunger travel and mounting them accordingly.
SPRING PRESSURE
Most probe series have two spring pressures, LIGHT and HEAVY. Use the light spring pressure in densely populated areas of your vacuum fixture to insure proper actuation. High pressure springs penetrate contamination more effectively, and should be used in low density areas or in mechanically actuated fixtures where vacuum is not used. As a rule of thumb, use high pressure when possible. If you can't "pull" a sufficient vacuum on your board, then the spring pressure per sq. inch may exceed atmospheric pressure and a light spring pressure may be needed. Spring forces may be +/- 20%.

SMT Probes

A full line of 50 mil. (1,27 mm) center SMT Test Probes are available. These probes are designed for use in applications where probe tip to PCB target accuracy and electrical performance is critical. Look for the "SMT" symbol in the product specification pages as your guide in selecting a SMT probe.
POINTING ACCURACY (P)
The radial movement of the plunger tip from the centerline of the mounting location is considered the pointing accuracy. The buildup of tolerances between components as well as the probe design and assembly techniques dictate the achievable pointing accuracy for a particular probe. While critical to the success of SMT PCB testing, it is but one consideration in maximizing tip-to-target accuracy. Other factors include fixture and PCB manufacturing tolerances. These include tooling pin alignments, drill hole perpendicularity, probe platen flatness as well as PCB artwork alignment. Ostby Barton manufactures probes in a combination of sizes (dimensional configurations), tip styles, and spring pressures to accommodate a variety of testing factors.

Cyclo-Soldered Probes

The actuation of your vacuum fixture can pull solder fumes, fluxes, dust and smoke from the air. These elements are then deposited, together with friction-induced plating wear, on the bearing surfaces of your probe. Resistance can then skyrocket from under 50 milliohms to 2-3 ohms. In addition, high resistance readings may be intermittent, which makes it nearly impossible to find and replace the problem probes. To address this situation, Ostby Barton originated and developed the Cyclo-Soldered test probe. This unique process provides a continuous, metallurgically bonded unit ensuring low and stable electrical constant resistance from one end of the probe to the other. When the bearing surfaces become completely insulated by contaminants, the spring (which is silver soldered to the plunger and barrel) takes over as the path of least resistance and remains constant throughout the probe's life. The maximum probe resistance is limited to that of the spring itself, which is typically under one ohm. The Cyclo-Soldered process is available on selected probes that are displayed in the products section of the catalog. Please consult the factory for more information.

High Current Probes

High current probes can carry 8-45 amps through a circuit. This is especially useful in non PCB test applications. The HC probe series provides low constant electrical resistance and excellent mechanical life on a variety of test centers. The special internal design provides higher current carrying capacity than "similar looking" probes. The stainless steel springs permit use in high temperature applications while their high pressure provides tip-to-target force minimizing constriction resistance.

Custom Probes

Ostby Barton has the industry's largest collection of custom probe designs. We had electrical contact design even before electrical contacts were adopted for ATE use. Chances are good that you'll find the solution you need off the shelf. But if your application demands a more unique approach, our engineers will work with you to develop the probe that meets your needs.

Receptacles

Five receptacle styles are available: CRIMP, SOLDER, WIRE WRAP, ROUND POST, and QUICK CONNECT. Some styles are only available in certain sizes (see specific probe series). See the TOOLS section for installation tips.

CRIMP
This reliable connection is used primarily on smaller probe sizes in high density applications where wire wrap isn't available or in situations where probe plate thickness inhibits the use of wire wrapping. Push-on terminals can also be used and are commercially available from most connector manufacturers.
SOLDER
This termination provides excellent electrical integrity for high reliability applications. It is used primarily in low density situations.
WIRE WRAP
These terminations are strong and provide excellent electrical integrity. It is the most common termination used in ATE fixturing. Connections can be made quickly by skilled technicians. Push-on terminals which fit the standard .025 in. (0,63 mm)square post can also be used.
ROUND POST
Round post receptacles with .025 in. (0,63 mm) diameter posts are used with .100 in. (2,54 mm) center connectors and/or ribbon cable assemblies for mass termination.
QUICK CONNECT
Quick Connect termination provides exceptional contact integrity and is available only on SMT receptacles. Connections can be made quickly and wiring mistakes can be corrected easily without damaging the receptacles.