Performance Testing and Quality Assurance

The first automatic spring probe tester was developed by ECT in 1978. It was designed for precise measurement of plunger travel and probe resistance to supplement mechanical life cycle tests. Today, our proprietary test systems have evolved to become the most sophisticated probe test equipment in the industry.
ECT probe test protocols enable us to establish rigid product standards, enhance product performance, and ensure consistently high quality standards. They are an integral part of our Statistical Process Control (SPC) programs, and an essential component of product development projects. And every test is designed to measure performance based on the real-world demands of ATE environments.

DPT-1000 Probe Tester

This fully-programmable tester provides precise measurement of electrical resistance and mechanical performance over the life of the probe. It will perform true four-wire (Kelvin) or three-wire tests.
A computer-controlled variable eccentric drive system mechanically cycles the spring probes and accurately sets the plunger stroke. Cycle speed is adjusted to specific probe type and test requirements. Fifty probes of similar dimensional characteristics can be monitored simultaneously and measured independently. Collective data output can be in tabular or graphical format, in as many as five data subgroups.

Probe Test Setup

The probe test is initiated by entering the type of test (four-wire or three-wire), plunger travel and electrical measurement instructions. This input determines electrical current levels and frequency of resistance measurement cycles. A printout records each measurement as the test proceeds.
At the end of the test, the computer prints a summary report comparing the probe to established standards. The test report includes a high/low/average graph of probe resistance, and an overall performance rating.

True Four-Wire Kelvin Test Circuit

By using this circuit, the effect of such variables as oxidation or contamination of test points, spring force, tip configuration, etc. (which are application specific) is eliminated from the resistance measurement. It is superior to other circuits because it is not dependent on tip geometry, and it eliminates lead resistance in the test circuit.

Three-wire Test Circuit

This circuit measures resistance of the spring probe and the contact resistance of the probe tip. Contamination on the probe tip or conductor bar affects the measurement, but it is nearly impossible to measure or predict. Although the effect can be minimized by coating the conductor bar with gold, palladium, solder or copper, the remedy may fail to duplicate real world conditions, especially for loaded board testing.
Because the conductor bar is relatively clean and flat, this test will generally produce better results for probes with flat or radius contact surfaces than those with sharp points or cutting edges. In a real loaded board test environment, sharp tips are far better able to penetrate board surface contaminants.
Three-wire tests circuits may also produce different resistance measurements for two probes which are identical except for spring force. This results from the constriction resistance between the probe tip and the conductor bar.

DPT-500 Probe Tester

This custom-designed mechanical life-cycle tester evaluates wear characteristics caused by probe design, plating materials and thickness, and base metals. The tester contact plate is made of a variety of materials and finished to resemble the geometry of a real PCB. The angle of the contact plate can be adjusted to simulate typical alignment difficulties encountered in test fixtures.
The DPT-500 can perform accelerated life tests at 30,000 cycles/hour, or high-speed life tests up to 90,000 cycles/hour with variable plunger compression settings. Information from this tester is used to evaluate the effect of side loading on resistance and probe life.

Quality Control and SPC

In 1980, ECT became the first probe manufacturer to establish a quality goal of zero defects. Since then, we've continued to impose more stringent manufacturing standards and quality control processes to meet that goal. We call it the Quality Network Program.

Incoming Inspection with SPC

Advanced computerized Statistical Process Control (SPC) programs support incoming inspection of every component. Surface finish, plating thickness, hardness, straightness, diameter, spring force, spring life and receptacle detent force are monitored for consistency. A sampling control plan ensures that a trend toward a control limit is readily identified and corrected.

In-process Assembly and Inspection

Every probe and receptacle component undergoes additional inspection during and after final assembly. This includes 100% inspection and electrical testing on our proprietary computer-controlled automatic assembly machines. Probe components are checked for straightness, compressed height and plunger O.D. Post-assembly functional inspection identifies "stickers", and verifies overall length, plunger travel and crimp location. Then a four-wire Kelvin test compresses the probes to recommended working travel, and a resistance measurement is compared to the programmed threshold. Any failed probe component or assembly is immediately rejected into a scrap container.
Spring probe assembly samples from each production lot are inspected for crimp depth and strength, extended stickers, and general overall appearance. Wire wrap receptacle assemblies are tested for crimp strength, bending, crimp depth and location, pull force and vacuum leak. Only assemblies that pass this inspection proceed to finished goods quality control.

Final Quality Assurance

In final test, an SPC program records measurements of finished products against programmed parameters. The program is similar to that used for incoming inspection, but tests are more rigorous. In four-wire Kelvin testing, for example, a production sample will be subjected to as many as one million cycles.
We do everything possible to ensure that our probes are the very best in the industry. That's why so many of our customers depend on our Quality Network Program as their incoming inspection.

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