integrated circuits

With the rapid development of integrated circuits, many electrical and automotive applications are utilizing high current capabilities.probe test system How to safely and effectively test such products is becoming a new challenge.

We have also developed high current test probes, which are typically used to test large charge/discharge devices.

In terms of parametric characteristics, the value of the current to be delivered is the most important property of a high current test probe. Physically, a test probe generates heat when carrying current as a conductor, and it can simply be assumed that the probe can continue to operate at the high currents passing through the test probe without burning out the probe.

The measurement of heat is expressed in terms of temperature, and the value of the high current that can be tested by a high current probe is determined by the fact that the high current probe can withstand the temperature and still work smoothly. We can test high currents with temperature through the device.

Why do we need to choose a bullet contact test probe for high current test conductors? Why not use a copper bar contact?

Because compared to copper bars (rigid leads), spring contact test probes will safely protect the DUT with long-lasting cycles under automatic test fixtures.

So for high current test probes, the spring is the key point component, usually the spring will be made of stainless steel wire or music wire, both leads are made of carbon (high resistance ratio components), for example, stainless steel's electrical resistivity reaches (20 ℃): 0.73 Ω-m.RF probes In contrast, copper's electrical resistivity is only 1.75x10-8 Ω-m. If we straighten the spring made of stainless steel wire and test it, the resistance is up to 40Ω. tested, the resistance is upwards of 40 Ω. Therefore, if a current is passed from the spring to the barrel, this can be fatal. The spring will be burned and jammed. The probe will now become rigidly pinned and will most likely destroy the DUT.Typically, thin spring wires will burn black or melt at temperatures of up to 120°C. This is a problem for high current test probes. This is the biggest challenge for high current test probes. So we need to consider that the internal structural design of high current probes affects the ability to pass high currents. , The heat dissipation problem of the high current probe will affect the performance of carrying high current.

We need to pay attention to many issues during the high current testing process:

1. The high current probe is not in full contact with the DUT

Full contact with the DUT is very important for very contact testing,probe card the conductor can pass the signal or current from the DUT to the tester through the test probe, here will illustrate some of the situations where the wrong probe tip is used.

2. Weak spring probe force

Spring probe force is the pressure of the test probe which produces the power to make a tight contact or contact with the DUT, so it is very important to help the probe to make a tight contact with the DUT.

3. Poor heat dissipation of the fixture plate.

The probe is a conductor that contacts the high current DUT and emits heat during high current testing. Poor heat dissipation affects the high current test and heat buildup can cause the spring to burn out. This is why heat dissipation is so important.

4. Misunderstanding between continuous and peak current.

We misunderstand continuous current and peak one. Continuous current is a stable value provided continuously. It is very different from peak current, which is the highest current value that occurs during the supply. They are very different considerations in high current probe design.

5. use poor test probe socket connection methods.

6. It is a mistake to choose a common test probe to test a high current DUT.

See Figures (6) and (7), standard contact probes will burn out when used in high current testing, but high current test probes will not burn out, the spring is burned black in Figure (6).

How to increase the effectiveness of high current probes in high current testing:

1. Increase the contact area between the probe and the DUT.

Increasing the contact area will result in a larger current crossing area, thus expanding the path of the charge. The following are some suggestions for better contact between the probe tip and the DUT.

2. Increase the contact spring force.

Applying optical force probes is not useful, for high currents we need to overestimate by 25% compared to standard probes. The penetration depth of the higher force contact is deeper than the standard force contact, see Fig. (14) and Fig. (15). So it is clear that the contact of Fig. (15) between the pad and the tip of the probe is more stable and has a larger contact area.

3. Improvement of material and structural properties of test probes

The material of high-current spring probes is very important. In contrast to standard contact probes, the high-current versions are made of highly conductive materials and are treated with a rare metal plating to ensure high current carrying capacity.

The structural design adds more and more extreme contacts inside the probes to stably carry high currents.

4. Creating more space for heat dissipation

Heat dissipation is the problem after heat generation, when the current passes through the conductor, the conductor will generate heat, the ratio of dissipation and generation is less than 1, the dissipation will reduce the burning rate. We should use dissipative fixture plates for mounting probes and sockets.

5. Pay attention to the important effects of continuous and peak currents

Paying more attention to continuous current and peak current, high current probes face severe power testing situation, continuous current is a kind of persistent electrical signal. So they are very important.

6. Improving the connection between probes and sockets

What we have done is to make sure that more tightly, better, screws and inserts can be tightened between the probe and the socket.