Wafer Level CSP (WLCSP) – Bump on I/O and Redistribution

FlipChip utilizes several dielectric materials that offer various advantages such as improved electical performance and reliability. In addition the dielectric will planarize the die surface and add a stress buffer layer improving the solder joint reliability. Because of this WLCSP die typically do not require underfill during assembly.

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Bump on I/O WLCSP

WLCSP's use pre-formed solder spheres of 200μm to 500μm in diameter to routinely bump device pitches ranging from 0.35 to 0.8 mm pitch and reflowed for final bump heights of 160μm to 400μm. In this process, the bumps can be placed directly on the device I/O's or the bump can be redistributed to a more desirable die location. Redistribution of the I/O can be achieved by utilizing a sputtered metal or copper plated RDL trace.

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RDL WLCSP

UltraCSP® WLCSP – Bump on I/O and UltraCSP® WLCSP – Redistributed

UltraCSP® is our patented Wafer Level Chip Scale Package (or WLCSP) process. Since its introduction in 1998, UltraCSP has become the industry’s standard for WLCSP. Bump heights for the process range from 160μm to 400μm depending on pitch. In this process, pre-formed solder spheres of 200μm to 500μm in diameter are placed on the wafer and reflowed. The bumps can be placed directly on the device I/O’s or the signal may be redistributed to a more desirable die location. Typically, the number of bumps per die is 4 to 100. Die bumped with UltraCSP® do not require underfill until the bump array reached the 6x6 to 7x7 size. For larger bump arrays underfill may be needed depending on the reliability requirements of the particular application. The lack of underfill makes it easy to migrate TSOP or QFP to UltraCSP®. UltraCSP® is classified as a JEDEC Level 1 compliant packaging option.

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Bump on I/O UltraCSP®

FlipChip's UltraCSP® WLCSP technology utilizes a proprietary dielectric material, which offers improved electrical performance and reliability over other polymer repassivation options. In addition to its advanced dielectric material, the product family incorporates a growing number of subtractive sputtering and semi-additive electroplated Cu based metallization options targeting specific customer needs. For example, some of the product breadth over the past few years has been developed in response to the evolving board level requirements of portable handheld products.

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RDL UltraCSP®