Lead Frame Protective Pads for Precise Contact Etching
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Solution Overview
Problem
Conventional lead frame etching processes result in varying contact shapes and sizes due to differing etching rates along different directions, leading to incorrect positioning and connection issues in semiconductor packages.
Innovation Solution
A lead frame design with metallic protective pads having defined connecting reserved areas and processing areas of varying widths, made of different materials, to ensure consistent etching and accurate contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional lead frame etching process is used, then manufacturing cost is reduced, but contact shape and size precision deteriorates due to varying etching rates in different directions
Solution Approach 1:
The patent applies local quality by creating an asymmetric protective layer structure where the protective layer has different thicknesses in different regions. Specifically, the protective layer thickness in the first direction is intentionally made different from the thickness in the second direction, allowing each region to be etched at appropriate rates to achieve uniform contact hole dimensions despite inherent etching rate variations
Solution Approach 2:
The patent changes the physical parameters of the protective layer by controlling its thickness distribution. By adjusting the protective layer thickness in different directions (first direction versus second direction), the etching process parameters are effectively modified to compensate for directional etching rate differences, ensuring consistent contact hole shapes and sizes
2Reliability
If protective layer is flattened along forming direction, then chemical resistance is improved, but etching rate becomes anisotropic causing contact positioning errors
Solution Approach 1:
The patent deliberately introduces asymmetry in the protective layer design. The protective layer is configured with different thicknesses in the first direction compared to the second direction. This asymmetric structure compensates for the anisotropic etching behavior, allowing the etching process to produce symmetric, uniformly sized contact holes despite the directional differences in etching rates
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 shape and size errors in contacts, ensuring proper connection and positioning of semiconductor packages by maintaining consistent etching rates and sizes.
Implementation Method 1
the middle part of each lead is removed by process such as chemical etching
Data Source
AI summary
A lead frame is provided and includes: a die pad; and a plurality of connecting pads provided around the die pad, and bottom surfaces of at least a portion of the connecting pads are formed with metallic protective pads, each of the metallic protective pads is defined with a connecting reserved area and a processing area around the connecting reserved area, and the metallic protective pads and the connecting pads are made of different materials. By the implementation of the lead frame, the shape and size of each contact of an electronic package made using the lead frame technology are without errors caused by the different etching rates along a direction perpendicular to a forming direction and along a direction parallel to the forming direction, thereby avoiding problems such as poor contact due to the errors in the shapes and the sizes of the contacts.