Flexible Substrate Mounting via Sequential Curing and Reflow
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Solution Overview
Problem
Conventional Surface Mount Technology (SMT) processes often result in false welding when mounting Surface Mounted Components (SMCs) or Surface Mounted Devices (SMDs) on flexible substrates, leading to lower yield and reliability of electronic packages.
Innovation Solution
A method for mounting electronic devices on flexible substrates involves providing conductive patterns on the substrate, forming solder bumps on these patterns, dispensing a thermosetting material, and attaching the electronic device using both the solder bumps and the thermosetting material. The thermosetting material is cured at a lower temperature before the solder bumps are reflowed, ensuring a secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SMT process is used to mount SMC/SMD on flexible substrate, then the mounting process is simple, but false welding occurs frequently leading to lower yield and reliability
Solution Approach 1:
The patent applies preliminary action by curing the thermosetting material before reflowing the solder bumps. This sequence ensures the flexible substrate is rigidified in advance, preventing false welding during the subsequent reflow process. The mounting process attaches the electronic device to the flexible substrate using both the thermosetting material and solder bumps, with the thermosetting material cured at a lower temperature first, then the solder bumps are reflowed at a higher temperature.
2Strength
If solder bumps are reflowed at high temperature, then the solder connection is strong, but the flexible substrate may deform or warp
Solution Approach 1:
The patent applies preliminary action by curing the thermosetting material before reflowing the solder bumps. This sequence ensures the flexible substrate is rigidified in advance, preventing false welding during the subsequent reflow process. The mounting process attaches the electronic device to the flexible substrate using both the thermosetting material and solder bumps, with the thermosetting material cured at a lower temperature first, then the solder bumps are reflowed at a higher temperature.
Solution Approach 2:
The thermosetting material acts as an intermediary that provides temporary mechanical support and stabilization to the flexible substrate during the high-temperature reflow process. By rigidifying the substrate beforehand, it mediates between the thermal stress of reflow and the substrate's structural integrity, preventing warping while allowing strong solder connections to form.
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 method significantly reduces the occurrence of false welding, enhancing the reliability and yield of electronic packages by maintaining a firm connection between the electronic device and the flexible substrate even during the reflow process.
Implementation Method 1
heating the flexible substrate to a first temperature to cure the thermosetting material
Implementation Method 2
heating the flexible substrate to a second temperature higher than the first temperature to reflow the solder bumps
Data Source
AI summary
A method for mounting an electronic device on a flexible substrate is disclosed. The method comprising: providing the flexible substrate with conductive patterns on its front surface; forming solder bumps on the conductive patterns; dispensing a thermosetting material on the front surface of the flexible substrate; attaching the electronic device on the flexible substrate via the solder bumps and the thermosetting material; heating the flexible substrate to a first temperature to cure the thermosetting material; and heating the flexible substrate to a second temperature higher than the first temperature to reflow the solder bumps.