Thin Board Assembly Sheet With Edge Through Holes
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Solution Overview
Problem
The existing imaging device components, particularly the imaging element-mounting boards in cellular phones, face challenges in reducing thickness to minimize device height while avoiding thermal distortion and ensuring durability during mass production, as thin flexible circuit boards (FPCs) are prone to warping and breakage during the singulation process.
Innovation Solution
A board assembly sheet with through holes along the end edges or phantom lines is used, allowing for reduced impact during cutting with a dicing blade, minimizing damage and contamination, and enabling efficient production of multiple mounting boards with reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a thin flexible circuit board (FPC) is used to reduce thickness, then the total thickness of the mounting board is reduced, but the board becomes easily broken during singulation and mass production
Solution Approach 1:
A temporary reinforcement layer is applied to the rear surface of the thin FPC before the singulation process. This preliminary action strengthens the board to withstand cutting forces during dicing, and the reinforcement layer is removed after singulation is complete, leaving the final thin mounting board intact.
2Stability of the object's composition
If the FPC is made thinner to reduce thermal stress and warping, then thermal distortion is reduced, but the board becomes more susceptible to breakage during cutting
Solution Approach 1:
The reinforcement layer is applied in advance to the thin FPC before singulation. This preliminary strengthening allows the thin board to maintain its thermal stability while temporarily gaining the mechanical strength needed to withstand the cutting process without breaking.
3Strength
If a thick rigid-type wiring circuit board with metal plate reinforcement is used, then the board has high strength and resistance to breakage, but the total thickness increases
Solution Approach 1:
Instead of permanently reinforcing the board with a thick metal plate, a temporary reinforcement layer is applied only during the critical singulation process. This allows the board to have high strength during manufacturing while maintaining thin thickness in the final product.
Solution Approach 2:
The reinforcement layer serves its purpose during singulation and is then discarded (removed) after the process is complete. This temporary use of reinforcement material allows the final product to remain thin while still benefiting from enhanced strength during the vulnerable manufacturing stage.
4Productivity
If multiple FPCs are singulated from an FPC assembly using a dicing blade, then mass production efficiency is improved, but the thin FPCs are easily damaged during cutting
Solution Approach 1:
The reinforcement layer is applied to all FPCs in the assembly before the dicing process begins. This preliminary strengthening enables high-speed automated cutting of multiple boards simultaneously while protecting each thin FPC from damage during the singulation process.
Data Source
AI summary
A board assembly sheet includes a plurality of mounting boards each for mounting an electronic component. The mounting boards are defined in the board assembly sheet. The mounting board has a total thickness of 60 μm or less. The board assembly sheet has a through hole passing through the board assembly sheet in a thickness direction. The through hole is formed to be along an end edge of the mounting board or along a phantom line extending along the end edge.