WLCSP & MEMs Test Socket Overview

RTI’s cartridge carrier system brings a structured, test-in-tray approach to chip-scale and die-level device evaluation. By separating device retention from electrical contact, the carrier protects delicate WLCSPs, MEMS, and other small packages while enabling seamless transfer between single-site and multi-site test sockets. Engineers gain the flexibility to run characterization, reliability, and burn-in testing on the same set of loaded cartridges without re-handling devices. This method reduces handling damage, preserves alignment across test phases, and delivers consistent results in both engineering and production environments.

Inside the Cartridge

Device-specific cartridge carriers are designed to protect small and fragile DUTs both during tests and in between test sequences. Cartridge carriers are a two-piece design consisting of a drilled multi-site base and a screw-down retaining lid. They do not include any pogo pins or electrical contacts and must be used with compatible test sockets to complete the interface between the DUT and PCB. Customize and standardize your own cartridge and socket footprint to best support your test equipment and carry devices safely through every stage of test.

Key Features

• Drilled for very fine pitch devices ≥ 0.3 mm
• Universal drilled arrays justify A1 to the top-left corner
• Number of test sites per cartridge based on DUT size and pin count
• Consistent alignment features for use with different socket designs
• Low-magnetic permeability materials available for lid, cartridge, and hardware
• ESD-sensitive materials available for lid, cartridge, and hardware
• Provides airflow across devices at each site
• Provides fine ball alignment across individual sites
• Can be drilled for arrays larger than the device size and made universal

Single Site Clamshell Sockets

These small-footprint clamshell test sockets provide electrical contact to a single DUT loaded in a cartridge carrier. Alignment posts positioned close to the pogo pins match alignment holes corresponding to the test site on the cartridge carrier.

Kelvin contacts and custom footprints to match existing DUT boards are available. Single-site sockets are suited for retesting suspect devices that may have failed during multi-site testing.

• Precise alignment of each test site to pin footprint using guide pins and slotted socket bases
• Different pin models available to meet electrical requirements
• Suitable for hand test applications using step-and-repeat until all sites are tested
• Test socket and lid add no pressure to the DUT beyond the upward pin force
• Designed for fine-pitch and low pin-count devices

Single-site universal array test sockets may be available. Cartridges loaded with different DUT footprints but of the same pitch can be mounted — the cartridge masks out unused pins and only the necessary pins engage the DUT.

Multi-Site Clamshell Sockets

With a footprint nearly matching the cartridge carrier, these clamshell test sockets provide electrical contact to two or more DUTs loaded in a cartridge. Keyed alignment posts positioned at the long edges of the socket align the cartridge to the pogo pin arrays and assist in vertical loading. Multi-site clamshell sockets save valuable time in higher-volume testing by reducing device load/unload between sequences.

• Ideal for mid- to high-volume characterization and in-circuit testing requiring quick cartridge changeover
• Multi-site universal array pogo pin block accepts cartridges with various array sizes of the same pitch
• Floating pressure plate in the clamshell lid ensures even distribution of force over the cartridge and holds it flat against the socket base as pins engage the DUTs
• Test socket and lid add no pressure to the DUT beyond the upward pin force
• Fine alignment features provide consistent device alignment across individual test sites between cartridge and socket

Multi-Site No-Lid Sockets

These low-profile test sockets share a footprint with the cartridge carriers and minimize space around the test sites. This allows more sockets (and test sites) to be placed on a single DUT board, increasing throughput during extended burn-in applications. Cartridge carriers mount directly to the socket with four screws. Removable protective covers prevent debris from collecting on pogo pins when sockets are not in use.

• Socket X/Y dimensions match cartridge size
• Backing plate adds stiffness and prevents warping when mounted
• Very low profile improves access to the topside of devices
• Open design improves airflow around devices during burn-in
• No clamshell lid — access to DUTs through cartridge lid openings
• Can be drilled and populated as universal; compatible with multiple cartridge designs sharing alignment, mounting, and site positioning