High Speed Solder Deposition on Flexible Substrates
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Solution Overview
Problem
Conventional solder reflow processes are slow and prone to solder spattering, leading to undesired bridging and contamination due to the limitations of isotropic conductive adhesives and the requirement for substrates to be in contact before curing, which hampers the efficiency and speed of electronic device assembly.
Innovation Solution
A system and method that applies solder paste to a flexible substrate while it travels at high speeds, using an oven with independently controlled zones for infrared and convective heat to cure the solder paste efficiently, allowing for faster processing and reduced curing time without the need for substrate contact during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional solder reflow processes are used, then solder paste can be cured, but the processing speed is slow and solder spattering occurs leading to bridging and contamination
Solution Approach 1:
The oven is divided into multiple independently controlled heating zones (preheat zone, reflow zone, cooling zone) with each zone operating at different temperatures. This segmentation allows optimized processing in each zone - the preheat zone prepares the substrate without causing spattering, while the reflow zone cures the solder paste rapidly, and the cooling zone solidifies it quickly, thereby increasing overall processing speed while minimizing solder spattering
Solution Approach 2:
The patent employs dynamic temperature parameter changes across different zones and time periods. The preheat zone uses lower temperatures to gradually heat the substrate, the reflow zone rapidly increases temperature to cure the solder paste, and the cooling zone quickly reduces temperature to solidify the solder. These parameter changes enable fast processing while controlling solder behavior to prevent spattering and bridging
2Temperature
If isotropic conductive adhesives are used, then lower processing temperatures and higher print resolution are achieved, but adhesion loss at high temperatures and joint cracking occur
Solution Approach 1:
The patent uses anisotropic conductive adhesives instead of isotropic ones, which maintain their conductive properties and adhesion strength at higher temperatures. The controlled temperature profile across different zones ensures the adhesive cures properly without degrading, preventing adhesion loss and joint cracking while enabling higher processing temperatures for faster curing
3Reliability
If substrates are required to be in contact before curing, then curing can occur, but the processing time increases and flexibility is reduced
Solution Approach 1:
The preheat zone performs preliminary heating of the substrate and solder paste assembly before the actual reflow curing process. This preliminary action prepares the materials for rapid curing in the reflow zone, reducing the required dwell time and eliminating the need for prolonged substrate contact, thereby decreasing processing time while maintaining curing quality
Solution Approach 2:
The patent implements a dynamic heating process where temperature and processing conditions change continuously across different zones and time periods. This dynamic approach allows the substrate to be processed in a continuous motion through the oven zones without requiring static contact positions, reducing processing time while ensuring proper curing through optimized temperature profiles at each stage
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
Enables high-speed deposition and curing of solder paste on flexible substrates, improving processing efficiency and reducing solder spattering, thereby enhancing the speed and accuracy of electronic device assembly beyond conventional methods.
Implementation Method 1
passing the flexible substrate through an infrared heating zone to rapidly heat and melt the solder paste
Implementation Method 2
convective heating zone to complete the curing process
Implementation Method 3
cooling zone to solidify and cure the melted solder paste
Data Source
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AI summary
The present disclosure related to a flexible electronic substrate assembly and a method and system of processing solder paste onto an electrical substrate. The assembly includes a flexible substrate having a solderable medium provided along the flexible substrate. A pattern of solder paste may be cured to a portion of the solderable medium. The solderable medium may be a generally continuous construction or a patterned construction relative to the flexible substrate. The substrate may be unwound from a roll of substrate material before solder paste is deposited thereon. The flexible electric substrate assembly may be formed though a roll to roll process. Infrared heat may be applied to the substrate with the solder paste deposit as the substrate is traveling along the process direction to reflow the solder paste as the substrate is traveling along the process direction at a high rate of speed.