| Low and Consistent Resistance When considering interconnection, many of our customers tell us that their most important concern is low and consistent resistance. IDI probes and custom connectors are designed to provide consistent, low resistance, dependably from one cycle to the next.
Low resistance is a major benefit of probe technology. In the spring contact probe, the total contact resistance is determined by two primary factors:
1 - The bulk resistance of the contact material
2 - The internal contact resistance between the plunger and barrel These sources of resistance can be engineered in the probe design to keep the total contact resistance low and stable, minimizing fatigue both internally and externally, throughout the life of the contact.
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One way spring probe technology insures that current flow is continuously low is through a technique called “biasing”. Biasing is the mechanism that forces the plunger against the internal wall of the barrel. As shown below, there are four different biasing techniques that can be used in spring-loaded probe design:
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| The first method of biasing is the bias spring. The spring is designed to force the plunger to the barrel. This is the least aggressive method of biasing and is a cost effective and sufficient design for many applications. |
| | The second method of biasing, a more aggressive approach, is the bias plunger. An angle is cut on the backside of the plunger. The spring bears against this angle, forcing the plunger to the internal wall of the barrel.|
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| | The third method of biasing is the patented eccentric drill design. This biasing technique involves back-drilling a plunger intentionally off-center creating a lateral force for the spring to press the plunger wall to the wall of the barrel. The eccentric drill design allows for a larger spring cavity, which provides greater compliance or travel in a shorter, more compact probe design. |
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| | The fourth and most aggressive biasing technique is the bias ball. The bias ball is similar to the bias plunger but with the added value of a ball bearing between the spring and the plunger. The ball bearing aggressively forces the plunger against the barrel wall providing the lowest and most consistent resistance for the most demanding applications. |
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Bias Spring Design |
Bias Plunger Design |
Eccentric Drill Design |
Bias Ball Design |
