Dual-Layer EMC Circuit Package Warpage Control
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Solution Overview
Problem
Integrated circuit packaging faces challenges with panel warpage due to differing coefficients of thermal expansion between the circuit and the epoxy mold compound, leading to bending or warping during cooling and solidification.
Innovation Solution
A method involving the use of a first epoxy mold compound with a specific coefficient of thermal expansion (CTE) and a second epoxy mold compound with a higher or lower CTE, applied in layers to control thermal expansion and minimize warpage, where the second compound is dispensed after the first has gelled to prevent mixing and ensure proper placement of the circuit device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single epoxy mold compound is used to package the circuit, then the packaging process is simple, but panel warpage occurs due to differing coefficients of thermal expansion between the circuit and the EMC
Solution Approach 1:
The packaging structure is segmented into multiple EMC layers with different CTE values. The first EMC layer (closer to the circuit) has a lower CTE to match the circuit's thermal expansion, while the second EMC layer (outer layer) has a higher CTE. This segmentation allows each layer to compensate for thermal expansion differences, preventing panel warpage while maintaining manufacturing feasibility through sequential deposition processes.
Solution Approach 2:
The packaging uses a composite structure composed of two different epoxy mold compounds with distinct coefficients of thermal expansion. This composite material approach creates a multi-layer system where the combined thermal expansion characteristics of both layers balance out the CTE mismatch between the circuit and packaging, effectively reducing warpage without complicating the manufacturing process.
2Stability of the object's composition
If the second EMC is dispensed before the first EMC gels, then the EMC layers mix together, but this prevents proper placement and positioning of the circuit device
Solution Approach 1:
The first EMC layer is deposited and allowed to gel to a predetermined degree before the second EMC layer is dispensed. This preliminary gelling action creates a stable, semi-solid foundation that prevents mixing with the second layer while still maintaining enough workability for circuit device placement. The gelled first layer acts as a stable substrate that supports subsequent deposition and device placement operations.
Solution Approach 2:
The viscosity and gelation state of the first EMC layer are dynamically controlled during the packaging process. By allowing the first EMC to gel to a specific degree before adding the second layer, the system transitions from a fully liquid state (prone to mixing) to a semi-solid gelled state (stable but still workable). This dynamic control of material state enables both layer separation and ease of device placement.
3Stability of the object's composition
If the EMC layers are kept completely separate without intermixing, then layer stability is maintained, but design flexibility in package dimensions is reduced
Solution Approach 1:
The EMC layers are allowed to intermix only in specific local regions at the interface between layers, rather than maintaining complete separation throughout. This localized intermixing occurs at the boundary between the first and second EMC layers, creating a transition zone that enhances bonding and design flexibility. The bulk regions of each layer maintain their distinct properties and stability, while the local interface region provides adaptability for various package dimensions and configurations.
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 reduces panel warpage by compensating for thermal expansion differences, allowing for more design flexibility in circuit package thickness, length, and width, and preventing delamination by allowing minor intermixing of the EMC layers.
Implementation Method 1
upon the first EMC gelling over a predetermined period of time
Implementation Method 2
differing coefficients of thermal expansions (CTEs) among the circuit and the EMC may cause the packaged circuit to warp or bend upon solidification and cooling of the EMC
Data Source
AI summary
In some examples, a circuit package includes a packaging, and a circuit device in the packaging, where the packaging comprises a first EMC having a first coefficient of thermal expansion (CTE), and a second EMC having a second CTE higher than the first CTE. The second EMC is on the first EMC that has gelled over time.