Offset Test Pads for WLCSP Final Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing WLCSP testing procedures require separate and costly probe cards for final testing, which can be inefficient and costly, especially for devices with non-standard pin or ball configurations, limiting access to all test signals and increasing expenses.
Innovation Solution
The implementation of a WLCSP design with offset pads and redistribution layers (RDL) that connect pads to solder balls, allowing for reuse of the same test card for both wafer and final testing, reducing costs and facilitating access to all test signals without exposing pads to potential corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate probe cards are used for wafer testing and final testing, then all test signals can be accessed, but testing costs increase significantly
Solution Approach 1:
The patent implements a universal probe card design that can perform both wafer-level testing and final device testing through the same physical card. The probe card includes test pads that are accessible at both processing stages, eliminating the need for separate probe cards and reducing overall testing costs while maintaining full test signal accessibility
Solution Approach 2:
The patent structures the test pads and interconnects so that testing infrastructure is established during wafer fabrication. The test pads are created alongside functional pads in the same fabrication process, and the probe card design anticipates both wafer and final device testing needs, allowing a single probe card to serve multiple purposes throughout the manufacturing lifecycle
2Ease of operation
If pads are exposed for final testing, then electrical testing can be performed, but pads become susceptible to corrosion
Solution Approach 1:
The patent introduces an offset test pad structure that acts as an intermediary between the functional pad and the probe card contact point. The offset test pad is electrically connected to the functional pad through a test interconnect, allowing electrical testing to occur on the offset pad while the functional pad remains protected and covered, thus enabling testing without exposing the functional pad to corrosion
Solution Approach 2:
The patent segments the pad structure into functional pads and offset test pads. The functional pads are covered and protected, while separate offset test pads are provided specifically for testing purposes. This segmentation allows the functional pads to remain protected from corrosion while still enabling electrical testing through the offset pads that are electrically connected to them
Data Source
AI summary
A device configured for WLCSP, can include: a first pad; a test pad offset from the first pad; a first RDL path that connects the first pad to the test pad; and a second RDL path that connects the test pad to a solder ball. In another case, a device configured for WLCSP can include: a first pad; a test pad offset from the first pad; a first RDL path that connects the first pad to a solder ball; and a second RDL path that connects the test pad to the solder ball. A wafer having devices configured for WLCSP, can include: a first device having a first pad; a second device having a test pad; a first RDL path that connects the first pad to a solder ball; and a second RDL path that connects the test pad to the solder ball.