PTC Device Lead Frame Concave Recesses for Solder Adhesion
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Solution Overview
Problem
The production efficiency of PTC devices is reduced due to protruding solder paste and excess epoxy resin adhering to the jig during the manufacturing process, making it difficult to remove the devices from the jig and requiring cleaning, which hampers productivity.
Innovation Solution
The use of leads with concave portions that prevent the protruding solder paste and epoxy resin from contacting the jig walls, thereby reducing adhesion and facilitating easier removal and cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder paste is placed between the metal electrode and the lead, then the members are electrically connected, but the solder paste protrudes out and solidifies adhering to the jig wall, making it difficult to remove the PTC device from the jig and requiring cleaning
Solution Approach 1:
The lead frame serves as an intermediary component between the PTC element and the external circuit. The lead frame's structure with recessed portions and bent portions prevents solder paste from directly contacting the jig wall, while still providing reliable electrical connection. This intermediary structure solves the contradiction by maintaining electrical connectivity while preventing harmful adhesion to the jig.
Solution Approach 2:
The lead frame is segmented into multiple functional portions: a body portion, bent portions for electrical connection, and recessed portions for containing solder paste. This segmentation allows each portion to perform its specific function - the recessed portions contain the solder paste to prevent adhesion, while the bent portions provide electrical connectivity, thus resolving the contradiction between reliable connection and production efficiency.
2Reliability
If excess epoxy resin is applied to form the oxygen barrier coating, then the PTC element is protected, but the excess resin adheres to the jig wall, requiring cleaning and reducing productivity
Solution Approach 1:
The lead frame acts as an intermediary barrier between the epoxy resin and the jig wall. The recessed portions of the lead frame contain the excess epoxy resin, preventing it from adhering to the jig. This allows sufficient epoxy to be applied for proper protection of the PTC element without the harmful side effect of jig adhesion, thus resolving the contradiction between protection and productivity.
3Manufacturing precision
If the jig has concave portions to hold the assembly, then the members are kept in position during manufacturing, but the protruding solder paste and epoxy resin adhere to the jig wall, making removal difficult and requiring cleaning
Solution Approach 1:
The lead frame serves as an intermediary that maintains positioning precision while preventing adhesion. The recessed portions of the lead frame contain the protruding materials (solder paste and epoxy resin), preventing them from contacting the jig wall. This allows the jig's concave portions to effectively hold the assembly for precise manufacturing without the subsequent problem of adhesion and cleaning, thus resolving the contradiction between manufacturing precision and productivity.
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 approach enhances the productivity of PTC device production by minimizing the adhesion of solder paste and epoxy resin to the jig, allowing for more efficient assembly and reducing the need for cleaning, thus improving overall production efficiency.
Implementation Method 1
the solder paste 24 is place on the metal electrode 22, and the cell side lead 16 is placed on the solder paste so that an assembly of these members is formed. Thus formed assembly is passes through a reflow furnace so as to melt the solder paste followed by solidifying the molten solder paste by cooling
Implementation Method 2
Such assemblies are passed through the reflow furnace to connect the members together via the solder
Implementation Method 3
an epoxy resin is applied onto the side of the PTC device to from a coating layer, followed by curing the layer to form the oxygen barrier coating 26
Data Source
AI summary
The present invention relates to a new PTC device having a configuration with which protrusion of solder paste and/or an excess portion of epoxy resin do not adversely affect a jig. Such PTC device 30 comprises a PTC member 32 and leads 34 and 36 electrically connected to both sides of the PTC member the PTC member comprises a PTC element 38 and metal electrodes 40 and 42 placed on both sides of the PTC element respectively, each lead is electrically connected to the metal electrode respectively via an electrically conductive connection portion 50, and at least one 36 of the leads has a concave portion which is defined with a bottom portion 44 located adjacently to the metal electrode of the PTC member and a wall portion 46 surrounding the electrically conductive connection portion which connects the leads to the metal electrode.