With the rapid development of integrated circuits, many electrical and automotive applications have adopted high-current functions. How to safely and effectively test this type of product is becoming a new challenge. 

And we also developed high-current test probes which are usually used to test large-scale charging and discharging equipment. 

Seeing from the parameter characteristics, the current value to pass over is the most important performance on high current test probes.

Physically speaking, a test probe will generate heat when it is carrying the current as a conductor, We can simply consider the probe can continue to work at the high current that passes over the test probe and doesn’t burn the probe.

The measure of heat is expressed by the temperature, the high current probe can test the value of high current is determined by that the high current probe bears the temperature and still works smoothly. We can test the high current with the temperature of the device.

Why do we need to choose a spring contact test probe for a high-current test conductor?

Why not use a copper bar to contact?

Because compared to the copper bar( a rigid lead), the spring contact test probe will safely protect the DUT with durable cycles under the automatic test fixture.

So to a high current test probe, the spring is the key point component, usually the spring will be made from stainless steel wire or music wire, and both of those two wires are made of carbon( a high resistance ratio element), For example, The resistivity of stainless steel reaches(20℃): 0.73Ω·m. In contrast, the resistivity of copper is only 1.75 × 10-8 Ω·m. if we straighten a stainless steel wire-made spring and test it, the resistance is high over 40Ω. So if the current passes from the spring to the barrel this causes a fatal influence. the spring will be burned and stuck. The probe now will become a rigid pin and break the DUT in high probability.

Generally, the thin spring wire will burn black or melt at a high temperature of 120°C. This is the biggest challenge of the high current test probe.

So we need to consider.

• The internal structure design of the high current probe affects the aptitude to pass high current.

• The heat dissipation problem of the high current probe will affect the performance of carrying the high current.

We have to pay attention to a lot of problems in the current test process

1. The high current probe is not fully contacting the DUT

   Fully contact with the DUTs is very important to every contact test, which means the conductor can pass the signal or current from the DUT to testers through the test probes, here will illustrate some situations that use the wrong probe tips.

① Sharp Contact to soldering pad                   ② Flat Contact to soldering pad                      ③ Round Contact to soldering pad                      ④ Flat Contact to dip                       ⑤ Crown Contact to dip

2. The spring probe force is weak

    The spring probe force is the pressing power of the test probe, it generates the power to puncture or contact tightly to DUTs, so helping the probe tightly contact the DUTs is very important. 

3. The heat dissipation effectiveness of the fixture board is not good.

   A probe is a conductor to contacts the big current DUT, which will dissipate the heat during the big current test process. The heat dissipation is not good which will affect the high current test result, heat accumulation will cause spring burnout. That is why heat dissipation is so important.

4. Misunderstanding between continuous current and peak current.

     We misunderstood the continuous current and peak one, continuous current is supplied continuously as a stable value. it is very different from a peak current, which appears the highest current value during the power supply. There are different considerations on high current probe design.

5. Adopted bad test probe receptacle connection method.

6. It's wrong to select the normal test probe to test high current DUTs.

     See Fig.⑥and Fig.⑦, the standard contact probe will be burned when it is used in the high current test, but not the burn of the high current test probe, the spring is burned black in Fig.⑥.

⑥The standard test probe was burned during a high-current test                                     ⑦ High current test probe was not burned                                                                       ⑧ Buring probes during the high current test

How to improve the high current probe's effectiveness on high current testing

1.     Increase the contact area between probes and DUTs

Increasing the contact area is making the current crossing area larger which enlarges the channel of the electric charges. Here are some suggestions for better contact between probe tips and DUTs.

⑨Serrated tip to soldering pad                               ⑩Serrated tip to soldering pad                               ⑪Flat tip to golden pad                               ⑫Round tip to golden pad                               ⑬Star tip to via

2. Increase the contact spring force.

     It's not useful to apply the light force probes, for high currents we need to overestimate 25% compared to standard probes. The puncture depth of larger force contact is deeper than the standard force contact (Fig.⑭ and Fig.⑮）. So obviously the contact of Fig.⑮ is more stable and has more contact area between the soldering pad and probe tip. 

⑭Standard force contact to soldering pad           ⑮Larger force contact to the soldering pad                         ⑯Few contact points                                    ⑰More contact points

3. Improve the materials and structural characteristics of the test probes

    Materials to high current spring probes are very significant. Compared to the standard contact probes, high current versions are made of high conductive material with uncommon metal plating treatment to ensure the high current carry aptitude.

    The structural design increases more and more extremely contact inside of the probe to carry high current stability.

 ⑱Rare metal-plated treatment                                                                                                       ⑲Contact probe springs

4. Create more space for heat dissipation

     Heat dissipation is the issue after heat generating, when the current is passing over the conductor, the conductor will generate the heat, the dissipation, and generating ratio is less than 1, and the dissipation will reduce the burning issue rate. We should use the dissipated fixture boards to install the probes and sockets.

5. Pay attention to the important influence of continuous current and peak current 

    Pay more attention to the continuous current and peak current, the high current probes face the tough power test situation, continuous current is a persistent electric signal. So they are important.

6. Improve the connection between probes and receptacles

     What we do is to make sure more tighter much better, screwing and insertion are both can be tightened between the probes and receptacles.

 Here is the link for high current probes selection Click Here

7. Improve the connection between the receptacles and the wires 

    Soldering receptacles will be better than any other ones. It's stable and lasting for carrying the high current.

Soldering Receptacle for thick wire tightly connection                                                Insertion receptacle for  wire inserting, it is not so strong