Best Solder Bump Vertical Probe Cards
Solder Bump Vertical Probe Cards are an important part of the wafer-level test process. Sensitive devices, including flip chip die and those using low-k dielectrics, require special attention to avoid damage during testing. Traditionally, probe card manufacturers have reduced contact force by improving planarity, changing the shape of the probe tip, and introducing new probe tip materials. However, the required contact force is still too high for these probes to handle the number of pins on flip-chip devices that are being tested.
VS-Series
VS-Series Solder Bump Vertical Probe Cards offer superior performance and high test efficiency for array bumping applications. They address the complexities of wafer-level testing for finer pad pitches and array patterns, delivering superior contact precision, stable contact resistance for optimal first pass yield and improved device uptime.
As the number of pads and array patterns on devices increases, traditional cantilever probe card technologies have limitations that increase with the number of DUTs and rows of pads. For example, a 2-row probe card with cantilever probes is shown in Figure 3.
In addition, the CRES layer that forms on the surface of the probe tip and bump can cause false failures due to the high resistance between the pad and the probe tip. In order to overcome this, additional travel is added in the z-axis (referred to as overtravel). This forces the CRES layer to break through, exposing fresh metal to contact the probe tip. This can damage the bump and the component below.
VE-Series
The VE-Series of Solder Bump Vertical Probe Cards offer a solution to the challenges of higher probing requirements. As the number of pad rows on devices increases, standard cantilever probe technologies become less efficient.
The buckling-beam principle, used in this type of probe, generates a non-linear spring characteristic that distributes force evenly over all contacts. This enables efficient contact with a broad range of device pitch, including upcoming devices that have pad sizes as small as 40x40um.
In addition to the buckling-beam principle, probe needle technology has evolved by improving taper consistency and increasing material enhancements. These improvements include smaller diameter, higher-strength tungsten and tungsten-rhenium wires and polymeric coatings to improve contact-to-needle isolation.
RS-Series
The RS-Series is a suite of Solder Bump Vertical Probe Cards designed to address the challenges associated with probing devices that have multiple peripheral pads. These logic configurations require high parallelism and finer pad pitches for efficient testing, but traditional cantilever styles of probe cards have limited performance as the number of rows or DUTs increases.
In addition, the RS-Series probe cards have been developed to meet a wide range of requirements for testing ICs with higher temperatures than those required by standard cantilever technologies. These temperature requirements are often a differentiator between different ICs, as the change in physical dimensions of probes as a result of changing temperature can cause contact failures during test.
The RS-Series is available in crown-type and flat-type specifications. These products can be manufactured with MEMS technology, which allows them to offer higher contact precision and stability. In addition, they allow for single pin replacement, which minimizes maintenance costs. The RS-Series are also designed to minimize cross-talk between probes, which can be a problem with conventional vertical style technologies.
RS-Plus
RS-Plus Solder Bump Vertical Probe Cards feature a crescent DUT layout to minimize the number of touch downs and achieve even scrub across wafer pieces. These DUT layouts enable optimal utilization of tester resources, resulting in high test yield and efficiency.
To improve the probing efficiency, longevity, and reliability of a probe, it is important to analyze the mechanical deformation and stress of interconnect structures such as solder balls and Cu pillar microbumps during contact with the probe tip. This analysis can help optimize the probe’s structural design and materials to ensure that the device is tested successfully, without causing excessive probe marks or damage to the solder ball or microbump.
We simulated the deformation behavior of NiCo and Au-NiCo probes, as well as copper pillar microbumps and TSV structures, using ANSYS 2019. Figure 6a shows the von Mises stress distribution map of the NiCo probe during contact with a solder ball at an overdrive of 150 um. It reveals that the maximum stress occurred at the center of the probe tip area.
