Wire Bond Mesh Filters Filler Particles in Semiconductor Packages
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Solution Overview
Problem
Semiconductor packages face precision issues due to stress induced by filler particles in the mold compound, particularly large filler particles that cause thermal expansion mismatches, affecting the accuracy of components like capacitors in analog devices.
Innovation Solution
A wire bond mesh is implemented over the circuit in the semiconductor die to filter out large filler particles, reducing stress by keeping them at a distance from the circuit, and a stress buffer layer is used to mitigate further stress variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mold compound with filler particles is used to protect the semiconductor die, then the die is protected from the outside operating environment, but stress variations occur across the die due to thermal expansion mismatches between filler particles and resin
Solution Approach 1:
The patent segments the mold compound into two distinct layers: a first mold compound layer containing filler particles and a second mold compound layer free of filler particles. This segmentation isolates the stress-generating filler particles from the semiconductor die by placing them in the first layer, while the second layer directly contacts the die and provides a stable, stress-free protective environment. The segmentation thus resolves the contradiction by spatially separating the protective function (filled layer) from the stress-stabilization function (filler-free layer).
Solution Approach 2:
The second mold compound layer acts as an intermediary between the semiconductor die and the filler-containing first mold compound layer. This intermediary layer transmits the protective enclosure function while filtering out the harmful stress variations generated by the filler particles. The intermediary layer thus mediates between the need for protection (provided by the filled compound) and the need for stress stability (required by the die), resolving the technical contradiction.
2Reliability
If large filler particles are used in the mold compound, then the protective coverage is enhanced, but the precision of analog devices deteriorates due to increased stress variations
Solution Approach 1:
The patent segments the mold compound structure to separate the functions of protection and precision preservation. The first layer with large filler particles provides robust protective coverage and environmental sealing, while the second filler-free layer ensures stress uniformity and maintains the precision of analog devices. This segmentation allows large filler particles to be used without compromising device precision, as they are isolated from the die by the second layer.
Solution Approach 2:
The patent applies local quality by giving different regions of the mold compound different compositions tailored to their specific functions. The first mold compound layer (远离 die) has high filler content for protection and structural integrity, while the second mold compound layer (靠近 die) has no filler particles for stress stability and precision preservation. This local differentiation resolves the contradiction by optimizing each region's properties for its specific role.
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 wire bond mesh effectively filters out large filler particles, reducing stress-induced variations and improving the precision and accuracy of semiconductor components by maintaining consistent thermal expansion across the die, thereby enhancing the performance of sensitive circuits.
Implementation Method 1
A wire bond mesh is implemented over the circuit in the semiconductor die to filter out large filler particles
Implementation Method 2
A coefficient of thermal expansion (CTE) is substantially different for the filler particles and the resin. Because the resin and the filler particles have substantially different values for CTE, the semiconductor package can experience local stress variations across the semiconductor die due to temperature changes.
Data Source
AI summary
A semiconductor package includes a lead frame having a die attach pad and a plurality of leads. A die is attached to the die attach pad and the electrically connected to the plurality of leads. The die includes a plurality of bond pads along a periphery of the die and a bond pad strip surrounding a circuit in the die. A first plurality of bond wires is bonded between first opposite sides of the bond pad strip. The first plurality of bond wires is aligned in a first direction. A second plurality of bond wires is bonded between second opposite sides of the bond pad strip. The second plurality of bond wires is aligned in a second direction. Mold compound covers portions of the lead frame, the die, the bond pad strip, the first plurality of bond wires and the second plurality of bond wires.