Molded Semiconductor Package Notches for Mold Flash Reduction
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Solution Overview
Problem
The molding process for packaging integrated circuit devices often results in mold flash, which reduces production yield and efficiency by affecting the number of units that can be fabricated over time.
Innovation Solution
A method involving a lead frame with die pads and contacts, where a mold compound is applied to encapsulate semiconductor devices, and a clamping mechanism using protrusions in mold chases to reduce mold flash and increase unit density, with notches formed on the mold compound to expose contacts and facilitate clamping during encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mold compound is injected to encapsulate semiconductor devices, then the devices are protected and packaged, but mold flash occurs which reduces production yield and efficiency
Solution Approach 1:
The patent applies preliminary action by forming notches in the mold compound before final encapsulation is complete. These notches are created by protrusions on the mold chase that clamp down on the lead frame during the molding process, pre-defining the edge geometry to prevent mold flash from occurring during subsequent encapsulation steps.
Solution Approach 2:
The patent segments the mold compound structure by creating notches that divide the otherwise continuous mold compound into distinct regions. This segmentation allows the mold compound to better conform to the lead frame edges and prevents excessive material flow that causes mold flash, thereby improving production yield.
2Reliability
If the mold compound encapsulates the entire substrate, then complete protection is achieved, but contacts cannot be accessed and unit density is reduced
Solution Approach 1:
The patent applies local quality by creating notches in the mold compound at specific locations where contacts need to be accessed. This allows the mold compound to provide complete protection in most areas while leaving localized regions exposed for contact access, thereby maintaining both protection and accessibility.
Solution Approach 2:
The patent extracts portions of the mold compound by forming notches that remove material at specific locations. This extraction creates openings that expose the contacts underneath, allowing electrical connections to be made while the rest of the device remains fully encapsulated and protected.
3Manufacturing precision
If protrusions are added to mold chases to clamp lead frames, then clamping force is enhanced and mold flash is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the protrusions on the mold chase to serve multiple functions: they act as clamping elements to hold the lead frame in position, and simultaneously function as forming tools that create the notches in the mold compound. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
Data Source
AI summary
An example electronic device includes a substrate having a die pad and a semiconductor device on the die pad electrically connected to the substrate. The device also includes a mold compound over the semiconductor device to provide a packaged electronic device. The packaged electronic device has respective side edges that extend from a first end to terminate in a second end at a distal surface of the mold compound that is spaced apart from the substrate. At least one side edge of the mold compound has a respective surface that is orthogonal to the distal surface and includes a notch extending inwardly from the respective surface.