Leadframe Trimming Sequence for Clean Dam Bar and Tie Bar Cuts
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Solution Overview
Problem
The premature wear of cutting tools used for removing dam bars and tie bars in integrated circuit (IC) packages leads to uneven mold flash remnants, IC package failures, and increased operating costs due to frequent tool replacement.
Innovation Solution
A multi-step trimming process using a cutting tool with an angular cutting tip to remove tie bars and a punch portion to remove dam bars, reducing wear and ensuring clean cuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-step trimming process is used to remove tie bars and dam bars, then the process is simple and fast, but the cutting tool wears prematurely creating jagged edges and uneven mold flash
Solution Approach 1:
The trimming process is divided into two separate steps: first removing tie bars, then removing dam bars. This segmentation allows each cutting operation to be optimized independently, preventing premature tool wear and maintaining cutting edge quality throughout the process.
Solution Approach 2:
The tie bars are removed first as a preliminary action before removing the dam bars. This sequence reduces the overall cutting load on the tool during the second step, extending tool life and maintaining precision.
2Loss of energy
If cutting tool is used frequently without replacement, then operating costs are reduced, but the cutting edge becomes worn and creates IC package failures
Solution Approach 1:
By segmenting the trimming into two steps with different cutting requirements, the tool experiences less cumulative wear per step, extending its usable life while maintaining reliability.
Solution Approach 2:
The multi-step process changes the cutting parameters (load, material being cut) between steps, reducing the rate of tool wear and allowing the tool to operate reliably for longer periods.
3Manufacturing precision
If cutting tool is replaced frequently to maintain quality, then cutting edge quality is maintained, but production time is lost and operating costs increase
Solution Approach 1:
The segmented trimming process distributes the cutting load across multiple lighter operations, reducing tool wear rate and extending the interval between tool replacements, thus maintaining productivity.
Solution Approach 2:
Removing tie bars first as a preliminary step reduces the burden on subsequent cutting operations, allowing the tool to maintain its cutting edge quality for longer periods.
4Productivity
If jagged cutting edges are allowed to continue cutting, then production continues without interruption, but uneven mold flash remnant is created leading to package failure
Solution Approach 1:
Dividing the trimming into two steps prevents the accumulation of damage from jagged cutting edges, as each step uses the tool while it is still relatively sharp, ensuring clean cuts and preventing package failures.
Data Source
AI summary
A method of fabricating electronic devices includes providing an array of leadframes, the array of leadframes including leads, tie bars, and dam bars and attaching a die to each leadframe of the array of leadframes. Wire bonds are attached from an active side of the die to the leads on each leadframe of the array of leadframes. A mold compound is formed over the die, the wire bonds, and a portion of the leads on each leadframe of the array of leadframes. A multi-step trimming process is performed to the array of leadframes to remove the tie bars and the dam bars from each of the leadframes of the array of leadframes.