Lead Frame Package With Stacked Chips for Higher Power Density
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Solution Overview
Problem
Existing lead frame packages for transient voltage suppression (TVS) diodes typically support only a single semiconductor chip, limiting power density and flexibility in design, as they do not efficiently accommodate multiple semiconductor devices within a single package.
Innovation Solution
A two-in-one lead frame package design that includes a die attachment pad sandwiched between two semiconductor chips, with each chip attached using clips and high-temperature or low-temperature attachment materials, allowing for two-channel support and various semiconductor combinations, enhancing power density and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single chip is supported in the lead frame package, then the device complexity is reduced and manufacturing is simpler, but the power density and design flexibility are limited
Solution Approach 1:
The patent transitions from supporting chips in a single plane to stacking multiple chips vertically on opposite sides of the lead frame. This dimensional change allows two chips to be accommodated in the same package footprint, effectively doubling the power density without proportionally increasing the package area.
Solution Approach 2:
The lead frame structure is designed to serve multiple functions simultaneously: it provides mechanical support for chips on both sides, acts as an electrical connection substrate, and enables different chip combinations (same or different types). This multi-functionality allows a single package design to accommodate various application requirements.
2Quantity of substance
If multiple semiconductor chips are supported in one package, then power density increases, but the attachment process complexity increases
Solution Approach 1:
The attachment process is segmented into distinct stages: first chip attachment using HTAM, then clip application with LTAM. This segmentation allows each attachment operation to be optimized independently and performed sequentially, reducing the overall process complexity compared to simultaneous multi-chip attachment.
Solution Approach 2:
HTAM is applied to the lead frame before chip mounting, creating a pre-prepared attachment surface. This preliminary action ensures that when chips are mounted, the attachment material is already in position and at the correct temperature state, simplifying the subsequent chip bonding process.
3Strength
If high-temperature attachment material is used, then chip attachment strength is improved, but the material may remelt during subsequent low-temperature soldering
Solution Approach 1:
The patent changes the temperature parameter profile through staged processing: first applying HTAM at high temperature for strong attachment, then performing subsequent clip soldering at lower temperatures. This parameter change ensures the HTAM remains stable during the second soldering operation while still achieving strong initial chip attachment.
Solution Approach 2:
LTAM serves as an intermediary material applied in clips that protects the HTAM-attached chip during subsequent soldering operations. The LTAM clips are soldered at lower temperatures that do not remelt the HTAM, thus mediating between the need for strong attachment and material stability.
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 two-in-one design increases power density by supporting two semiconductor devices, allowing for different product combinations and a two-channel design, while maintaining efficient attachment using conductive materials like Ag sintering epoxy or SAC solder, which do not remelt during low-temperature soldering.
Implementation Method 1
A first chip is attached to the first side, and the HTAM affixes the first chip to the die attachment pad
Implementation Method 2
The HTAM is dispensed onto a first lead portion and the first clip is attached between the first chip and the first lead portion, with the HTAM affixing the first clip to the first chip and the first lead portion
Implementation Method 3
maintaining efficient attachment using conductive materials like Ag sintering epoxy or SAC solder
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A lead frame package includes a first semiconductor chip, a second semiconductor chip, and a first lead frame. The first semiconductor chip is connected to a die attachment pad using a first clip. The second semiconductor chip is connected to the die attachment pad using a second clip. The die attachment pad is sandwiched between the first semiconductor chip and the second semiconductor chip. The first lead frame is connected to the die attachment pad.