Search
Close this search box.

Cantilever vs. Vertical Probe Card – A Comparison Guide

Vertical probe card structure

When testing IC wafers, the choice is usually between cantilever vs. vertical probe card types. One option presents a cost-effective solution, while the other is a more expensive choice for advanced testing needs. Below, we compare the two technologies, explaining their varying features and testing capabilities.

What is Different Between a Cantilever and a Vertical Probe Card?

The two probe cards mainly differ in the types of pins they use. That, in turn, means a difference in how they make contact with the wafer circuits. To help us understand that better, let’s examine the design of each device.

Cantilever Probe Card Technology

A cantilever type is named based on its testing probe design; the pins resemble a cantilever beam in construction. It uses an older technology where the pins are soldered to the PCB board and held at an angle.

During use, they touch the wafer surface from the side. This pin style creates flexibility but brings a few calibration difficulties, especially after a few thousand touchdowns.

Vertical Probe Card Technology

As the name implies, the vertical type has upright pins. If it’s micro-fabricated, the pins are tiny, with their pitch reduced to only a few microns, and capable of contacting many test pads in one touchdown.

Microscopic springs make the pins compressible and reduce pressure on the DUT (die under test). Vertical needles bring many test advantages but cause manufacturing difficulties, as we will see shortly.

Cantilever probe card pins are more challenging to set
Cantilever probe card pins are more challenging to set
Resource: https://www.semanticscholar.org

Cantilever Probe Card vs. Vertical Probe Card

The choice between a cantilever and a vertical probe card depends on many factors, such as accuracy needs, cost considerations, and if high throughput is critical. Here is a side-by-side comparison of the two to illustrate that.

Design and Structure

Vertical pins are radially arranged and mounted on an epoxy ring or other substrate. They’re shorter than cantilever types, especially when manufactured using MEMS, reducing contact pressure and resistance.

A cantilever probe pin projects its tip from the base, touching the wafer horizontally. They are also generally longer than the vertical types, which increases resistance during testing. Their sizes and shapes vary widely, depending on the test requirements.

Complexity Difference

The vertical style is a more complex design. It supports many needles in a small space, which makes it suitable for high-density probing. On the downside, the complexity makes it more challenging to design or make, increasing its cost.

Horizontal pins are a simple design. However, the design limits the number of test pins per unit area. As you can guess, it’s a more straightforward type to fabricate. That also means it’s less expensive to manufacture, making it more popular for low and medium-pin-count tests.

Testing Performance

Vertically arranged pins perform better. They are more accurate and produce more reliable results. They dent the device under test less, an attribute that makes it a more versatile choice, especially when testing delicate dies, such as flip chips.

Horizontally set needles are typically longer and have a higher contact resistance. That makes them less effective when compared to the upright pins. That said, their movement scrubs oxide off the pad surface. This action results in a cleaner surface and reduces resistance.

Cost Comparison

Despite its higher accuracy and precision level, the vertical probing card costs more to acquire, given its many tiny needles in a small space. However, they cost less to own or keep in good condition. The pins do not need realigning and are individually replaceable.

Cantilever designs are cheaper to fabricate but more costly to maintain since they need periodic corrections. As a result, they may cost more to own than the vertical types. Despite that, the acquisition cost is relatively high and not viable for less demanding applications.

Usability

Probe needles are less destructive when contacting the wafer surface at right angles, especially since their tips are microscopic and the resistance to current is less. Their dense design also supports high-speed testing, reducing time spent and allowing large-scale quality checks.

Horizontal needles have a higher inductance due to their larger size. They’re also more challenging to set, and their scrubbing action can damage the device under test. With these usability challenges, they fit low-production applications best.

A vertical-type probe card
A vertical-type probe card
Resource: https://hackaday.com

Cantilever vs. Vertical Probe Card in Applications

The many differences between cantilever and vertical probe needles make them suit different testing needs or applications. Below is a summary of the advantages of each card type.

Advantages of Using a Cantilever Probe Card

  • It has a more straightforward construction with fewer pins
  • It requires cheaper equipment and procedures to make
  • The needles are flexible when contacting the wafer horizontally
  • The pins’ rubbing action removes material contamination and improves electrical connection

These attributes make the cantilever card suitable for less demanding tests with low pin counts. It’s also a good choice if you’re not testing large or high-volume wafers, and parallel testing is not crucial. MEMS types perform better and are best if the pin count is higher than the traditional version can handle.

Advantages of Using a Vertical Probe Card

  • It has tiny pins with fine pitch, which makes it suitable for high-density testing
  • It offers reduced testing pressure
  • The needles are less challenging to set
  • It’s easier to maintain

With these benefits, the cards with vertical pins are necessary when testing high-density circuits or those requiring pin pitches below 40 microns. High-capacity tests also call for these card types, as they can contact many ICs simultaneously. Advanced types can test extremely tiny circuits using microscopic pins below a micron in size.

Conclusion

With the growing need for advanced testing methods and cost-effectiveness, choosing a vertical and cantilever probe card is becoming more critical. The cantilever style is a more economical alternative but is mainly suitable for less demanding applications. The other, although more costly, offers higher testing capabilities both in performance and output.

Share:

Table of Contents