Electrolytic Capacitor Pedestal Gap for Reflow Mounting Reliability
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Solution Overview
Problem
Chip-type electrolytic capacitors experience mounting failures during the solder reflow process due to increased internal pressure from vaporized solvent, causing the sealing member to expand and leading to poor connection strength and potential detachment from the circuit board.
Innovation Solution
A capacitor design featuring a convex portion on the pedestal's side wall with a gap between the caulking portion and the convex portion, allowing for expansion without separation from the pedestal, and a method involving solder reflow connection through a through hole in the circuit board with solder paste, ensuring secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitor is subjected to solder reflow process, then the lead terminal is connected to the circuit board, but the internal pressure increases causing the sealing member to expand and the capacitor to separate from the pedestal
Solution Approach 1:
The patent applies beforehand cushioning by providing a gap between the capacitor body and the pedestal before the solder reflow process occurs. This gap acts as a cushioning space that absorbs the expansion of the sealing member during heating, preventing the capacitor from separating from the pedestal. The gap is specifically designed to accommodate the expected expansion without causing detachment, thus maintaining connection strength while allowing for thermal effects.
Solution Approach 2:
The patent applies parameter changes by modifying the spatial relationship between the capacitor body and pedestal through the introduction of a gap. This structural parameter change allows the system to accommodate pressure changes and sealing member expansion during the solder reflow process, thereby maintaining reliable mounting without compromising connection strength.
2Reliability
If the sealing member is expanded due to internal pressure, then the capacitor body moves away from the pedestal, but the connection strength decreases causing mounting failure
Solution Approach 1:
The gap provided between the capacitor body and pedestal serves as a cushioning space that anticipates and accommodates the expansion of the sealing member during solder reflow. This beforehand cushioning prevents the capacitor body from moving away from the pedestal by providing a buffer zone, thereby maintaining manufacturing precision and preventing mounting failures.
Solution Approach 2:
The gap acts as an intermediary space between the capacitor body and the pedestal, mediating the interaction between these two components during thermal expansion. This intermediary space allows the sealing member to expand without directly transmitting the expansion force to the capacitor body, thus maintaining precise connection and preventing mounting failures.
3Volume of moving object
If the capacitor is mounted without a gap between the caulking portion and convex portion, then the structure is compact, but the capacitor separates from the pedestal during solder reflow
Solution Approach 1:
The gap between the caulking portion and the convex portion of the pedestal provides beforehand cushioning that prevents capacitor separation during solder reflow. This gap is strategically positioned to absorb expansion forces while maintaining a compact overall structure, thus achieving both space efficiency and mounting reliability.
Solution Approach 2:
The patent applies local quality by introducing a gap only in the specific region between the caulking portion and the convex portion of the pedestal, rather than throughout the entire structure. This localized gap provides the necessary cushioning space for reliability while maintaining compact dimensions elsewhere, optimizing both volume and mounting reliability.
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 design effectively prevents capacitor separation from the pedestal during high-temperature solder reflow, reducing mounting failures and enhancing connection reliability between the capacitor and the circuit board.
Implementation Method 1
when exposed to a high temperature state by the solder reflow process, solvent of the driving electrolyte is vaporized to increase the internal pressure of the electrolytic capacitor. Then, with the increase in internal pressure, by the sealing member is expanded
Implementation Method 2
when exposed to a high temperature state by the solder reflow process, solvent of the driving electrolyte is vaporized to increase the internal pressure of the electrolytic capacitor
Data Source
AI summary
To reduce the occurrence of capacitor mounting failure on a circuit board in the solder reflow process, the capacitor element is housed in the bottomed cylindrical outer case and sealed with a sealing member the open end of the outer case, the lead terminal derived from the capacitor element is formed through the sealing member a capacitor body, a base having a bottom surface portion and a side wall formed so as to surround the outer periphery of the capacitor body with a through hole through which the lead terminal penetrates, a capacitor having a convex portion protruding toward the capacitor body from the inner surface of the side wall, the caulking portion formed by caulking the side surface of the outer case the convex portion is disposed, providing a gap portion between the caulking portion and the convex portion.