Design, fabrication and characterization of MEMS probe card for fine pitch IC testing

• Conductive through-holes are in the ceramic substrate and polydimethylsiloxane layer.
• The high frequency behavior of polydimethylsiloxane was tested.
• The scrub mark on Al chip pad covers approximately 10 μm × 8 μm.
• This design improves the probe density and simplifies the fabrication process.
• The non-planarity of 816 probes is within ±3 μm.

This article introduces a novel type of MEMS probe card that uses polymer (polydimethylsiloxane, PDMS) as an elastic layer. The elastic layer provides the flexibility when the probes are in contact with the chip pads. Through-holes in the PDMS and the low temperature co-fired ceramic (LTCC) substrate lead the signals or power to the back side of the LTCC substrate. The proposed MEMS probe card configuration potentially improves the probe density and simplifies the fabrication process. The probes are formed by electroplating on the PDMS substrate. The PDMS elastic substrate probe card with a probe pitch of 100 μm was developed for area array pad testing. The contact force is approximately 18 mN when the probes overdrive is 20 μm. Coplanar waveguides structures can be fabricated on the PDMS surface. The measured insertion loss is 0.2 dB at 3 GHz.The test data exhibited that the PDMS elastic substrate probe card is suitable for high-frequency wafer level IC testing.