Lead Frame Holes and Dimples Control Solder Flow
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Solution Overview
Problem
Controlling the flow of solder in semiconductor packages is challenging, leading to issues like poor electrical connections and electrical shorts due to insufficient or excessive solder in certain locations.
Innovation Solution
The use of lead frames with strategically etched holes and dimples to control the flow of die attach materials such as solder, epoxy, or adhesives, which are reflowed to ensure proper distribution and prevent unwanted flow, thereby maintaining the position of components and preventing electrical issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is applied to component surfaces, then electrical connections are formed, but solder may flow to unwanted locations causing electrical shorts
Solution Approach 1:
The lead frame surface is segmented into multiple regions by creating holes and dimples that divide the solder flow path. These segmented regions act as barriers to prevent solder from flowing uncontrollably across the entire surface, while still allowing solder to reach intended connection points.
Solution Approach 2:
The lead frame is given non-uniform surface properties through strategically placed holes and dimples at specific locations. These local modifications create zones with different solder wettability and flow characteristics, allowing solder to be guided to desired areas while blocking flow in other regions.
2Object-affected harmful factors
If solder flow is restricted to prevent shorts, then electrical shorts are reduced, but insufficient solder may reach connection points
Solution Approach 1:
Holes and dimples are pre-formed in the lead frame before soldering to establish predetermined solder flow paths. These pre-configured features guide solder flow during the reflow process, ensuring solder reaches intended connection points while preventing overflow to unwanted areas.
Solution Approach 2:
The holes and dimples act as intermediary structures between the solder paste application point and the final connection locations. These intermediaries control and regulate solder flow, distributing solder evenly to multiple connection points while preventing excessive flow to adjacent areas.
3Object-affected harmful factors
If holes and dimples are added to control solder flow, then solder flow control is improved, but device complexity increases
Solution Approach 1:
The holes and dimples are integrated directly into the lead frame structure during the same manufacturing process, combining the flow control features with the base component rather than adding separate elements. This merging approach minimizes additional complexity while achieving solder flow control.
Solution Approach 2:
The lead frame surface geometry is modified by changing parameters such as creating localized depressions (dimples) and through-holes with specific dimensions and patterns. These parameter changes to the existing structure provide flow control functionality without fundamentally altering the overall device architecture.
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 effectively mitigates the risks of electrical shorts and poor connections by controlling the flow of die attach materials, ensuring reliable electrical connections and maintaining the position of components within semiconductor packages.
Implementation Method 1
one or more holes passing through the lead frame and coincident with the first and second surfaces, wherein the one or more holes are adapted to control fluid flow on the first surface
Implementation Method 2
controlling the flow of solder on component surfaces is important
Data Source
AI summary
A system, in some embodiments, comprises: a first surface of a lead frame; a second surface of the lead frame, opposite the first surface, said second surface having been etched; and one or more holes passing through said lead frame and coincident with the first and second surfaces, wherein said one or more holes are adapted to control fluid flow on said first surface.