Leadless Semiconductor Package with Etched Leadframe Cavities
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Solution Overview
Problem
Leadframe-based semiconductor packages face a minimum thickness requirement due to the need for strength and rigidity, which limits their ability to be made thinner than 100 μm, and thinner materials are difficult to handle without damage, posing challenges for reducing package height in consumer electronics.
Innovation Solution
A leadless semiconductor package design featuring a leadframe with a die paddle and bond pads having exposed back surfaces, where the leadframe is manufactured with a parent substrate etched on both sides to create elements and cavities, and a protective metal layer is plated onto these elements and cavity walls to prevent etching damage during packaging, allowing for thinner packages without compromising strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If leadframe thickness is reduced below 100 μm to achieve thinner packages, then package height is reduced, but the leadframe becomes too thin to handle without damage and lacks the strength and rigidity to withstand normal handling and manufacturing processes
Solution Approach 1:
The leadframe is segmented into discrete elements (die paddle, bond pads, leads) formed by etching cavities through the substrate thickness, rather than using a continuous thick leadframe. This segmentation allows thinning the overall package while maintaining structural integrity through strategic cavity placement and support structures
Solution Approach 2:
The invention transitions from a traditional thick leadframe structure to a thin substrate with through-thickness cavities, effectively moving the structural support function from the thickness dimension to the lateral dimensions through cavity walls and support structures
2Length of moving object
If leadframe thickness is reduced below 100 μm to achieve thinner packages, then package height is reduced, but special tooling and procedures are required to handle thinner material, representing significant additional expense
Solution Approach 1:
The cavities are formed through the substrate before final assembly, and the die paddle and bond pads are pre-positioned within these cavities. This preliminary structuring allows standard handling equipment to work with the thin substrate without requiring special tooling, as the critical structural elements are already in place
Solution Approach 2:
The invention uses a simplified thin substrate that copies only the essential functional elements (die paddle, bond pads, leads) rather than replicating the full traditional leadframe structure, reducing material thickness while maintaining functionality through selective feature reproduction
3Length of moving object
If leadframe thickness is reduced below 100 μm to achieve thinner packages, then package height is reduced, but thinner material becomes virtually impossible to handle without damage
Solution Approach 1:
The substrate incorporates built-in support structures and cavity walls that provide mechanical reinforcement before handling occurs. These pre-integrated support elements cushion and protect the thin substrate during manufacturing and assembly processes, preventing damage without requiring external handling aids
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 solution enables the production of semiconductor packages with reduced thickness, from 50 μm to 70 μm, maintaining structural integrity and reducing manufacturing costs by eliminating the need for support frames and complex handling procedures, while ensuring reliable electrical contact and thermal conductivity.
Implementation Method 1
a protective metal layer is plated onto these elements and cavity walls to prevent etching damage during packaging
Data Source
AI summary
A leadless semiconductor package includes a package body on a leadframe that includes a die paddle and a plurality of bond pads, none of which extend as far as a lateral face of the body. During manufacture of the package, molding compound is deposited over a face of the leadframe on which the die paddle and bond pads are positioned. After the molding compound is cured, a back side of the leadframe is etched to isolate the die paddle and bond pads, back surfaces of which remain exposed at a back face of the body. During manufacture of the leadframe, a parent substrate is etched to define the die paddle and a plurality of bond pads on one side of the substrate and a plurality of cavities on the opposite face.