Package Structure With Extended Test Pad For CP Yield
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Solution Overview
Problem
The shrinkage of openings in test pads after the redistribution layer (RDL) process affects the yield of chip probing (CP) tests, requiring improved package structures to enhance the operation window for probe pin placement.
Innovation Solution
A package structure with a widened flat portion of the test pad is achieved by reducing the thickness of the polymer layer below the extension portion, incorporating multiple polymer layers and a redistribution layer that extends onto the polymer layers, increasing the contact area and creating a larger CP test region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RDL process is performed with conventional polymer layer thickness, then the package structure is compact, but the opening of the test pad shrinks and CP test yield decreases
Solution Approach 1:
The patent applies dimensionality change by extending the test pad laterally onto the polymer layer surface, transforming the test pad from a purely planar structure to one that utilizes the vertical dimension for lateral extension. This creates an extended test pad region that increases the effective opening area without increasing the underlying metal pad size, thereby resolving the contradiction between maintaining compact packaging and ensuring sufficient CP test access.
Solution Approach 2:
The test pad is segmented into two functional regions: a base region over the metal pad and an extended region over the polymer layer. This segmentation allows the test pad to serve dual purposes - maintaining electrical connection through the base region while providing extended probing access through the lateral extension, thus improving CP test yield without compromising package compactness.
2Ease of operation
If the test pad opening is enlarged to improve CP test access, then the operation window for probe pin placement increases, but the electrical connection reliability may be compromised
Solution Approach 1:
The patent applies local quality by creating different functional zones within the test pad structure. The base region maintains direct electrical connection to the metal pad with high reliability, while the extended region over the polymer layer provides additional probing access. This local differentiation allows the test pad to simultaneously ensure electrical connection reliability and provide enlarged operation window for probe pin placement.
Data Source
AI summary
Provided is a package structure including a substrate, a metal pad, a first polymer layer, a second polymer layer, a redistribution layer (RDL), and a third polymer layer. The metal pad is located on the substrate. The first polymer layer is located on the substrate. The first polymer layer has a first opening which exposes a portion of a top surface of the metal pad. The second polymer layer is located on the first polymer layer. The second polymer layer has a second opening which exposes the portion of the top surface of the metal pad and a first top surface of the first polymer layer. The RDL covers the portion of the top surface of the metal pad and extends onto a portion of the first top surface of the first polymer layer and the second polymer layer. The third polymer layer is located on the RDL.