Circuit Board Test Pad Width Variation for Probe Contact
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Solution Overview
Problem
Conventional circuit boards are prone to deformation due to CTE mismatch between the substrate and circuit lines, leading to incorrect contact by probes during electrical testing, resulting in potential defective semiconductor packages.
Innovation Solution
A circuit board design with a substrate divided into portions, featuring first and second test pads of different widths, where the second test pads on the wider areas ensure correct contact by probes during electrical testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform width test pads are used on the circuit board, then the manufacturing process is simple, but probe contact precision deteriorates due to substrate deformation
Solution Approach 1:
The patent applies local quality by varying the width of test pads based on their location on the substrate. Test pads in the second area (outside the chip mounting area) are designed with a first width, while test pads in the first area (chip mounting area) are designed with a second width that is narrower than the first width. This local differentiation compensates for substrate deformation caused by CTE mismatch, ensuring that probes can accurately contact test pads despite the deformation.
2Device complexity
If the circuit board structure is simplified, then manufacturing is easier, but testing reliability deteriorates due to deformation-induced contact errors
Solution Approach 1:
The patent implements local quality by differentiating test pad widths in different areas of the substrate. The first area (chip mounting area) has test pads with a second width, while the second area (outside chip mounting area) has test pads with a first width. This localized structural variation addresses deformation issues without requiring complex overall board design changes, thereby maintaining manufacturing simplicity while improving testing reliability.
3Ease of operation
If all test pads have the same width, then the design is consistent and simple, but contact accuracy worsens when substrate deforms during thermal processing
Solution Approach 1:
The patent applies local quality by designing test pads with different widths in different areas of the substrate. Test pads in the first area (chip mounting area) have a second width, while test pads in the second area (outside chip mounting area) have a first width. This local differentiation maintains design consistency within each area while compensating for deformation effects, ensuring accurate probe contact despite thermal processing-induced substrate deformation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents testing errors by ensuring precise contact between probes and test pads, thereby avoiding false identification of circuit boards or semiconductor packages as defective.
Implementation Method 1
The conventional circuit board 10 is easy to be deformed (shrink or warpage) owing to CTE (coefficient of thermal expansion) mismatch between the substrate 11 and the circuit lines 12
Data Source
AI summary
A circuit board includes a substrate and a metallic layer. A first area and at least one second area are defined on a portion of the substrate, the second area is located outside the first area. The metallic layer includes first test lines disposed on the first area and second test lines disposed on the second area. A first test pad of each of the first test lines has a first width, and a second test pad of each of the second test lines has a second width. The second width is greater than the first width such that probes of an electrical testing tool can contact the first and second test pads on the circuit board correctly during electrical testing.