Conductive Terminal Cavity Design for Etch Control
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Solution Overview
Problem
The existing photolithography and etching process for forming cavities in conductive terminals is unsuccessful when the terminal length exceeds a certain threshold, leading to over-etching and unreliable connections with printed circuit boards, as the etchant etches too deeply, compromising the stability of the fillet slope inspection.
Innovation Solution
A novel conductive terminal design featuring a cavity with a first portion extending along at least half of the bottom surface and a second portion extending along less than half of the bottom surface, along with a similar configuration on the side surface, which reduces the amount of etchant used and prevents over-etching, while maintaining sufficient area for reliable AOI fillet slope inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cavity is formed in the conductive terminal using photolithography and etching, then the connection reliability with PCB is improved, but when the terminal length exceeds a certain threshold, over-etching occurs causing the etchant to etch too deeply, compromising the stability of the fillet slope inspection
Solution Approach 1:
The cavity is divided into two distinct portions: a first portion extending along less than half of the bottom surface and a second portion extending along at least half of the bottom surface. This segmentation allows the etching process to be controlled in stages, preventing over-etching while ensuring adequate cavity depth for reliable connections.
Solution Approach 2:
Different portions of the cavity have different dimensions and characteristics. The first portion has limited extent to prevent over-etching, while the second portion provides sufficient depth for connection reliability. This local variation in cavity quality addresses both the risk of over-etching and the need for reliable connections.
2Reliability
If the cavity extends along the entire bottom surface to ensure adequate connection area, then connection reliability is improved, but the amount of etchant used increases and over-etching risk increases
Solution Approach 1:
The cavity is segmented into a first portion (less than half of bottom surface) and a second portion (at least half of bottom surface), allowing controlled etchant consumption while maintaining adequate connection area.
Solution Approach 2:
The cavity provides sufficient (but not excessive) etching depth and area by extending the second portion along at least half of the bottom surface, ensuring adequate connection reliability without consuming excessive etchant or causing over-etching.
3Reliability
If the cavity is etched deeper to ensure adequate connection depth, then connection reliability is improved, but the fillet slope inspection becomes unstable and manufacturing precision decreases
Solution Approach 1:
The cavity depth is segmented into two portions with different extents, providing adequate connection depth through the second portion while the first portion's limited extent prevents excessive depth that would compromise fillet slope inspection stability.
Solution Approach 2:
The cavity geometry is optimized by controlling the extent of different portions, adjusting the parameters of depth and surface area to simultaneously achieve adequate connection reliability and stable fillet slope inspection.
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
This design mitigates the risk of over-etching, ensures compliance with customer specifications, and promotes proper AOI fillet slope testing by controlling the etch rate, allowing for stable connections between conductive terminals and PCBs.
Implementation Method 1
exposing the photoresist via the mask and developing the photoresist to produce a pattern on the photoresist
Implementation Method 2
etching the layer of conductive material using the pattern to produce a cavity
Data Source
AI summary
A package comprises a molding and a conductive terminal in contact with the molding and having a first surface exposed to a first surface of the molding. The conductive terminal includes a cavity having a first portion extending along at least half of the first surface of the conductive terminal and a second portion extending along less than half of the first surface of the conductive terminal.