Temperature-Dependent Underfill Tack for Passive Component Alignment
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Solution Overview
Problem
The challenge in mounting multiple passive components on a substrate efficiently is due to misalignment and adhesion issues during the reflow process, where strong adhesiveness of the underfill layer can cause residues on pickup nozzles and misalignment before the components are fixedly attached.
Innovation Solution
An electrode-equipped passive component with an underfill layer composed of a thermosetting resin, flux, and solvent, having a skin layer with tack power equal to or smaller than 25 mN/mm2 at room temperature and equal to or larger than 60 mN/mm2 at 40°C, which provides minimal adhesion during pickup and sufficient adhesion during reflow to prevent misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the underfill layer has strong adhesive power, then the passive component and mount target adhere well during reflow, but the underfill layer components attach to the pickup nozzle during pickup
Solution Approach 1:
The underfill layer's tack power is controlled to be ≤25 mN/mm² at room temperature (pickup condition) and ≥60 mN/mm² at 40°C (reflow condition). This temperature-dependent parameter change allows the same material to exhibit different adhesive properties at different stages of the process, preventing nozzle contamination during pickup while ensuring proper adhesion during reflow
Solution Approach 2:
The adhesive property of the underfill layer is made dynamic rather than static by designing it to change with temperature. The material transitions from a low-adhesion state at room temperature to a high-adhesion state at reflow temperature, allowing the system to adapt to different process requirements automatically
2Productivity
If many passive components are arranged on the mount target and subjected to reflow, then assembly productivity improves, but misalignment or rotation of passive components occurs before fixed attachment
Solution Approach 1:
The mount target is pre-heated to 40°C before the passive components are placed on it. This preliminary heating action ensures that when the components are placed, the underfill layer immediately exhibits high tack power (≥60 mN/mm²), providing strong adhesion that prevents misalignment or rotation during the subsequent reflow process, enabling parallel processing of multiple components
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
The solution effectively reduces residue attachment to pickup nozzles and ensures accurate alignment and adherence to the mount target during reflow, enhancing assembly productivity by maintaining low adhesion at room temperature and increasing adhesion at elevated temperatures.
Implementation Method 1
The skin layer has tack power equal to or smaller than 25 mN/mm2 at room temperature and equal to or larger than 60 mN/mm2 at 40° C.
Data Source
AI summary
An electrode-equipped passive component is an electrode-equipped passive component to be mounted on a mount target, and includes a passive component main body, an electrode provided on a mount surface of the passive component main body, and an underfill layer provided on the mount surface of the passive component main body. The underfill layer includes a thermosetting resin, a flux, and a solvent, and has a surface having a skin layer. The skin layer has tack power equal to or smaller than 25 mN/mm2 at room temperature and equal to or larger than 60 mN/mm2 at 40° C.