Automatic Probe Card Testing: how to Save Time and Money

What is a semiconductor probe card?

A semiconductor probe card is the electrical and mechanical interface that bridges the gap between an integrated circuit and the test equipment used during the wafer-level testing process of the IC.

The probe card makes contact with the IC bonding pads, allowing the tester to send electrical signals to the IC and measure its response. This helps identify any defects or malfunctions in the IC before it’s packaged and shipped out.

Overall, probe cards play a vital role in ensuring the quality and functionality of semiconductor chips: their construction must be free of defects, to ensure accurate and reliable verification of the IC integrity and performance.

Semiconductor probe card defects

Semiconductor probe cards are printed circuit boards designed to be very precise, as they include the microscopic probes that can make contact with the tiny pads on the IC. As they are precision instruments, any defects during construction can significantly impact their ability to function correctly.

Among the most common probe card defects, we find:

Short circuits
Open pins
Open tracks
Defective socket-to-PCB connection
Interrupted nets
Defective socket contacts
Weak components
Weak relays
Current leakage

These are just some of the construction defects that can plague probe cards. Even minor imperfections can cause major issues during testing, potentially leading to faulty ICs passing undetected or good ICs being rejected. Therefore, maintaining strict quality control measures throughout the probe card manufacturing process is crucial.

How to test semiconductor probe cards

Semiconductor probe cards are often tested utilizing the same type of semiconductor tester that the probe card will eventually be used with during IC testing. A dedicated diagnostic program specifically designed for probe cards is run on the tester.

Although it is quite common, this practice presents several disadvantages:

High costs: Semiconductor testers are expensive equipment, and using them for probe card testing takes away from their primary function of IC testing, impacting production efficiency
Time-consuming test development: Developing a comprehensive diagnostic program specifically for each probe card design can be time-consuming
Inadequate diagnostic capability: the functional test performed on the semiconductor tester is not able to detect all possible defects on a probe card
Long repair time: when a defect is detected, the tester is not able to provide a precise error message. The defective part is not identified, nor repair guidelines are provided: an expert test engineer has to make a deep, time-consuming analysis to repair the probe card
Hidden faults are not detected: defects that do not influence directly the functionality of the probe card can create instability or malfunctioning in production

To overcome these limitations, it can be convenient to use dedicated test equipment, separate from the actual semiconductor tester. These testers employ flying probes to make contact with designated test points on the probe card and perform a complete electrical testing.

Semiconductor probe card test equipment

SPEA flying probers are well-suited to exhaustively test any type of probe card, accurately verifying the correct functioning and parameter values for each component and net, so as to detect every process defect or component failure. They recognize faulty components, detect process defects (such as open pins or short circuits), identify components that perform out of their specifications and also “weak” components that are close to their end of life (e.g. relays).

The test is performed off-tester, without needing to spend hours on the IC tester of destination, while releasing the probe card testing from the required presence of an expert engineer. Precise diagnostic information is provided for every defect found, so that the expertise and time required to repair the probe card are greatly reduced.

SPEA flying probers do not need any application-specific hardware: the tester automatically generates the test program in a few hours, starting from the CAD data of the probe card. Even if CAD data is missing, the system is able to perform reverse engineering, useful to generate the test program or to replicate the probe card itself.

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Troubleshooting on defective semiconductor probe cards

Even probe cards that have performed well in the past can fall victim to a failure during their life cycle. In these cases, troubleshooting defective probe cards to pinpoint the root cause of the malfunction can be a time-consuming process for even the most experienced repair engineer.

SPEA flying probers can be profitably used not only to test fresh probe cards after assembly. Their capability of accurate probing, their measurement accuracy and precise diagnostics build a great added value also for troubleshooting on defective probe cards and performance verification after repair.

When a probe card breaks down during its use on the semiconductor test equipment, SPEA flying probers simplify the repair process. It is enough to run the flying probe test program to get a precise diagnosis of the faulty part(s), off-tester, reducing to minutes the downtime of the IC tester while minimizing the time to repair. Also the post-repair verification, before sending the probe card back to the production floor, can be readily performed on the SPEA flying probers, getting a full test coverage.

Monitor the performance of semiconductor probe cards

SPEA flying probers are not only able to detect probe card failures, but also to monitor key parameters of critical components by applying real working conditions. This “stress test” is able, for example, to give indication not only about the correct working of a relay at the moment of test, but also about the degradation state of its contacts. Based on this information, it is possible to preventively replace those components that are likely about to break, thus drastically reducing breaks on field and consequent downtimes.

Build a semiconductor probe card duplicate without CAD

In case probe card documentation and schematics are missing, SPEA flying probers are able to automatically rebuild the board data: net list, electrical schematics, part list and CAD data are automatically generated. The result of this reverse engineering operation can be used to generate the flying probe test program to be run on the probe card, or to make probe card replicates.

Conclusions

Testing semiconductor probe cards is an essential step in ensuring the quality and reliability of the entire integrated circuit (IC) manufacturing process: By ensuring the proper functioning of probe cards, manufacturers can prevent faulty ICs from reaching the market, improve production yield, and maintain consistent test results.

However, testing the probe cards using the actual semiconductor tester the probe cards will be used with is expensive and time-consuming, and can result ineffective in identifying certain defects.

The use of a flying probe tester to test semiconductor probe cards is faster and cost-effective, and offers the capability to detect all the possible defects, along the whole life cycle: from testing fresh probe cards before their introduction in the test floor, to troubleshooting of defective probe cards, periodic performance monitoring, reverse engineering.

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