Insulating Sheet Bending for Chip Package Creepage
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Solution Overview
Problem
Conventional chip package structures face challenges in increasing creepage and clearance distances between leads and heat dissipation devices to meet safety requirements for high voltage inputs, often resulting in high manufacturing costs and compromised heat convection due to the need for specialized shapes and excessive insulating materials.
Innovation Solution
Incorporating a bending insulating sheet or structure between the heat dissipation device and leads, which increases creepage and clearance distances without increasing package size or affecting heat convection, using materials like plastics, ceramics, or glass, and optionally employing insulating bumps, sleeves, or layers to enhance these distances further.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a heat fin in a special shape with a neck portion is employed to increase clearance distance, then the clearance distance between heat fin and leads is improved, but the manufacturing cost is significantly increased
Solution Approach 1:
An insulating sheet is introduced as an intermediary component between the heat dissipation device and the leads. This insulating sheet increases the clearance distance without requiring the heat fin to have a complex neck portion shape, thereby maintaining manufacturing simplicity while achieving the required electrical clearance.
2Length of stationary object
If grooves are formed on the molding compound surface to increase creepage distance, then the creepage distance between heat fin and leads is improved, but the design freedom of members is limited
Solution Approach 1:
The insulating sheet serves as a mediator that provides the required creepage distance through its material properties and dimensional design, rather than through grooves in the molding compound. This eliminates the constraint of avoiding grooves during member design, restoring design freedom.
3Reliability
If an excessively long flat-shaped insulating sheet is used to enlarge creepage and clearance distances, then the electrical insulation is improved, but the heat convection of heat sink is affected and package size increases
Solution Approach 1:
The insulating sheet is designed with local quality - it is positioned specifically where electrical insulation is needed (between leads and heat dissipation device) with minimal extension. This localized approach provides sufficient electrical clearance while minimizing interference with heat convection pathways and maintaining compact package dimensions.
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 effectively meets safety requirements for high voltage inputs by increasing creepage and clearance distances while maintaining a compact package size and efficient heat convection, reducing manufacturing costs by eliminating the need for specialized heat dissipation device shapes.
Implementation Method 1
The insulating sheet is disposed between the heat dissipation device and at least one of the leads
Implementation Method 2
a heat dissipation device having a top surface... The heat dissipation device is disposed on the top surface of the molding compound
Data Source
AI summary
A chip package structure including a substrate, at least one chip, a plurality of leads, a heat dissipation device, a molding compound, and at least one insulating sheet is provided. The chip is disposed on the substrate. The leads are electrically connected to the substrate. The molding compound having a top surface encapsulates the chip, the substrate, and a portion of the leads. The heat dissipation device is disposed on the top surface of the molding compound. The insulating sheet disposed between the heat dissipation device and at least one of the leads has a bending line dividing the insulating sheet into a main body disposed on the molding compound and a bending portion extending from the main body.