Power Module Resin Enclosure Rib Design for Insulation and Warpage Control
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Solution Overview
Problem
Power modules with encapsulated power elements connected to a metal base face challenges in maintaining electrical insulation and efficient heat dissipation due to warpage issues, leading to increased size and complexity in design, particularly when high power levels require larger insulation distances and thermal management.
Innovation Solution
A power module design featuring a resin enclosure with a body portion and rib portion that surrounds the metal base, providing enhanced insulation and heat dissipation while minimizing size, by protruding ribs on the bottom surface to increase the insulation distance and reduce warpage, thus allowing for a smaller form factor and improved thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulation distance between the lead frame and metal base is increased to ensure electrical insulation for high power modules, then the electrical insulation is improved, but the module area increases and the power module is enlarged
Solution Approach 1:
The patent transitions from increasing insulation distance in the lateral plane to increasing it in the vertical dimension by forming ribs that protrude upward from the resin enclosure bottom surface. The ribs create vertical insulation barriers between the lead frame and metal base, allowing adequate creepage distance without enlarging the module's footprint area.
Solution Approach 2:
The ribs are strategically positioned only at specific locations where insulation is most critical - surrounding the metal base at positions where the lead frame makes contact with the resin enclosure. This localized approach provides necessary insulation without adding unnecessary structure throughout the entire module, optimizing the balance between insulation and size.
2Reliability
If the size of the power module is increased to provide larger insulation distance, then the insulation is improved, but the thermal contraction of the encapsulation resin increases and the warpage amount becomes larger
Solution Approach 1:
The patent resolves the warpage issue by forming ribs that protrude vertically from the resin enclosure bottom surface, creating insulation barriers in the vertical dimension rather than requiring increased lateral dimensions. This approach provides the necessary insulation distance without increasing the overall module size that would exacerbate thermal contraction and warpage.
3Temperature
If the contact area between the metal base and heatsink is increased to improve heat dissipation, then the heat dissipation is improved, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent merges the insulation structure with the heat dissipation interface by forming ribs that protrude from the resin enclosure bottom surface to surround the metal base. This integrated design provides both electrical insulation and defines the heat dissipation contact area, eliminating the need for separate insulation components and simplifying the mounting process to the heatsink.
4Temperature
If retaining members such as retainer plates are added to restrain warpage and increase contact area with heatsink, then the heat dissipation is improved, but the number of parts increases and the fixing step becomes more complicated and time-consuming
Solution Approach 1:
The patent combines multiple functions into the resin enclosure itself: the ribs protruding from the bottom surface simultaneously provide electrical insulation, define the heat dissipation contact interface, and restrain warpage through their structural support. This eliminates the need for separate retainer plates or other retaining members, reducing the total part count and simplifying assembly.
Solution Approach 2:
The resin enclosure with integrated ribs serves multiple functions: it encapsulates the power elements, provides electrical insulation through the rib structures, defines the thermal interface with the heatsink, and restrains warpage. This multi-functional design replaces what would traditionally require multiple separate components, simplifying both the device structure and manufacturing process.
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 design effectively enhances electrical insulation and heat dissipation, reduces the module's size, and simplifies the mounting process to a heatsink, while minimizing manufacturing complexity and costs by controlling warpage and thermal expansion differences.
Implementation Method 1
it is required to insulate its outside electrode provided as one end of the lead frame connected to the front surface electrodes of the power elements, from the metal base connected to the rear surface electrode of the power element. The insulation distance between the lead frame projecting from the resin and the metal base exposed out of the resin, is determined by a creepage distance of the resin between the lead frame and the metal base.
Implementation Method 2
a metal base 3 for dissipating heat from the power element
Implementation Method 3
thermal contraction of the encapsulation resin is large and thus the warpage amount tends to be large
Implementation Method 4
it is required to strictly manage a linear expansion difference between the encapsulation resin and the frame member
Data Source
AI summary
The power module of the invention includes a power element, a metal base for dissipating heat from the power element, a lead frame electrically connected to electrodes of the power element, and a resin enclosure that encapsulates the power element so that one surface of the metal base and a part of the lead frame are exposed from the enclosure. The resin enclosure of the power module includes: a body portion in which the power element and a part of the lead frame are placed, and at a bottom surface of which the one surface of the metal base is exposed; and a rib portion which is placed on the bottom surface of the body portion so as to surround an outer periphery of the metal base, and is formed to protrude from the bottom surface of the body portion in a direction perpendicular to the bottom surface.