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WLCSP Package Interface Solutions

Challenges and Solutions for Contacting Wafer-Level Chip Scale Package Devices

Wafer Level Chip Scale Packages have been in use for over a decade years now, and the number of devices packed this way continues to grow at a significant pace. WLCSPs are primarily choice for mobile devices for this reason.

The other reasons to package at the wafer level are economic: The packaging itself is inexpensive and packaging at the wafer level allows testing at the wafer level. Final testing at the wafer level eliminates a test step compared the traditional wafer probe + final test.

WLCSP Package Test Solutions

Test Contactor / Probe Head Solutions

ACE Contactor / Probe Head

RF (cmWave) probe with bandwidth up to 40 GHz, homogeneous tip, and long life

ACE test contactor offers optimal RF performance for fine pitch FBGA, QFN and wafer-level packages for Power Amplifiers, RF switches and mobile communications. Supporting pitches down to 0.4 mm and superior performance for current consumption, gain, standard deviation, and power efficiency.

ACE probe head provides exceptional electrical performance, both DC and RF and is manufactured from HyperCore™ base material, which is a proprietary material of Cohu’s Everett Charles Technologies.

Compatible with all device types, platings, and pitches; and all test applications, including singulated devices, strip test and wafer-scale test. The materials and architecture create a very robust probe with a very working life and best yield. The electrical and mechanical performance, combined with the long probe life, deliver low overall cost of test, which are unprecedented for RF contactors.

Atlas Contactor / Probe Head

Optimal performance for large I/O count devices and high end digital test

QuadTech probe solution with cruciform tip strength that stands up to lateral force without bending, plus an enhanced compliance window to accommodate package stack height tolerance.

Atlas offers electrical performance that allows the customer to test to the true performance of the device. Atlas WLCSP test contactors achieve mechanical reliability with a rigid “cruciform” tip applied to Cohu’s QuadTech flat probe technology.  The Atlas offers a short electrical path, with lower capacitance and inductance, that is ideal for functional and AC parametric testing of WLCSP devices that require high system bandwidth and throughput gains in large multisite test applications.

The cruciform tip provides increased tip rigidity with a much greater immunity to breakage. The advantages for the customer include increased run times between contactor cleaning, increased probe life, increased yield, and reduced system down time for contactor maintenance.

cBoa Contactor / Probe Head

Uncompromised performance radial probe for the toughest test conditions

cBoa contactors and probe heads are the solution for contacting high frequency devices for package test or final test at wafer. The robust design and materials of the cBoa probe withstand the rigors of high-volume test by providing longer life and higher yield. The homogenous DUT side plunger provides longer run times between cleaning and increased probe life.

The cBoa features a stainless-steel spring for tri-temp testing and performs in operating temperatures of -55°C to +155°C. With a bandwidth up to 27 GHz, cBoa can be used to test some of the highest frequency devices.

The enhanced compliance window accommodates package stack height tolerances well.

cPython Kelvin Contactor / Probe Head

High performance kelvin contact for high volume production test

cPython Kelvin contactors and probe heads provide superior electrical and thermal performance with significant cost savings. This makes cPython Kelvin ideal for lab and high-volume production test of analog and mixed signal integrated circuits – for applications such as power control, A-D and D-A converters, audio, video, power amplifiers, photonics, optical MEMS and sensors.

cPython Kelvin probes are electrically isolated and mechanically independent force and sense paths for true Kelvin contact for taking accurate measurements, even under high current conditions. These robust probes provide hundreds of thousands of insertions or touchdowns, and a bandwidth up to 26 GHz.  cPython Kelvin probes can land on 0.4 mm pitch targets, and their tip spacing is 90 µm to land on small targets. cPython probes are available with homogeneous tips to optimize performance.

cViper Probe Head

Radial wafer probe solution down to 100 µm pitch with low loop inductance and high bandwidth and optional manual actuator for testing singulated die

cViper is an ultra-fine pitch probe head for RF and high speed digital WLCSP.  cViper is ideal for lab and large volume production test for precision analog, RF, sensors and mobility devices.  Low loop inductance and high bandwidth up to 27 GHz, cViper offers low and stable contact resistance for singulated devices or wafer-level test.   A variety of contact materials to optimize performance are available with device pitch down to 100 µm.

Gemini Kelvin Contactor / Probe Head

Industry preferred high performance, high value, low cost true kelvin QuadTech contacting solution

Gemini Kelvin probes and contactors provide a first-rate solution that effortlessly makes reliable, true Kelvin contact for high-volume final test of both singulated packages and wafer-level devices. Gemini Kelvin is an ideal solution for devices such as power controllers, A-D and D-A converters, power amplifiers and audio and video circuits.

At 3.22 mm test height, the Gemini Kelvin is an excellent all-around spring probe with low inductance, high bandwidth, and excellent current-carrying capacity. The DUT side tip design accurately maintains its 100 µm spacing for the life of the probe. Customers report typical probe life of 500 k to 800 k package insertions, or over 2M touchdowns at wafer-level test. The offset tip allows manageable board layout with a board-side spacing of 0.4 mm.

Mercury Contactor / Probe Head

Industry preferred high performance, high value, low cost QuadTech contacting solution

Mercury probes and contactors are excellent spring probes for the laboratory though they were designed with the robust qualities needed for high-volume production test. Their unique design ensures excellent plating quality for low, consistent resistance, long life, and high-test yields. Mercury probes are available with minimum pitches of 0.3 mm, 0.4 mm, 0.5 mm, and 0.8 mm, to provide the best performance at any device pitch. Mercury probes have bandwidths of up to 22 GHz, and can carry over 3 Amps of current. The Mercury is an excellent choice for any test application.

xWave Contactor / Probe Head

Highest performance and most robust RF broadband production solution for package, wafer, or OTA test to 100 GHz

The xWave contactor utilizes patented hybrid contacting technology to optimize RF performance and provide robustness for production testing of the most challenging cmWave and mmWave devices. Inside the xWave contactor are embedded patch antennas and coplanar waveguides for both wireless and wired communication.

In addition to wireless communication xWave contactors minimize the number of transitions between the DUT and tester through the use of co-planar waveguide structures that make direct connection with the DUT, bypass the PCB, and connect to the tester with either coaxial cable or waveguides.

  • Contacting Challenges

    • High parallelism
    • High ball counts (due to high parallelism)
    • Fine pitches (and getting finer)
    • Planarity issues (compared to wafer probe)
    • Challenging test requirements (compared to wafer probe)
    • Landing two probes for Kelvin applications
    • Making good contact without creating solderability issues
  • Contactor Features

    • Super-sharp tips
    • Lower-force probes
    • Large compliance windows
    • Fine-pitch Kelvin probes
    • Dimensionally-stable contactor materials
    • Mechanical simulation capabilities
  • Package Features

    • Smallest possible X/Y size: same as die for fan-in packages
    • Minimal Z height: thickness of wafer + thickness of redistribution layer + ball height
    • Lightest-weight package
    • Economical testing: final test on wafer eliminates one entire test step
    • Most cost-effective packaging
    • Best package for electrical performance