Lead Frame Pin Coating for High Voltage Isolation
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Solution Overview
Problem
High voltage integrated circuits face challenges in meeting the required creepage distance between pins due to the standard pin-to-pin pitch, leading to potential electrical breakdown and performance degradation, with existing solutions like depopulating pins or using larger leadframes being costly.
Innovation Solution
An additive deposition method such as inkjet printing, screen printing, or electrostatic spraying is used to coat a film of insulating ink over one or more external pins, increasing the creepage distance without removing pins, utilizing polymers or nanomaterials with high dielectric strength for effective insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the standard pin-to-pin pitch leadframe is used, then the manufacturing cost is low, but the creepage distance between pins is insufficient leading to electrical breakdown risk
Solution Approach 1:
An insulating coating layer is applied as an intermediary substance between adjacent pins on the leadframe. This coating acts as a mediator that increases the effective creepage distance without requiring physical separation of pins or redesign of the leadframe structure, thereby maintaining manufacturing simplicity while achieving high voltage isolation requirements
Solution Approach 2:
The electrical properties of the leadframe surface are changed by applying an insulating coating with high dielectric strength. This parameter change transforms the conductive surface into an insulating surface, effectively increasing the creepage distance and preventing electrical breakdown without altering the physical dimensions or pin configuration
2Reliability
If pins are depopulated to increase distance between remaining pins, then the creepage distance is increased, but the manufacturing cost increases due to tooling requirements
Solution Approach 1:
Instead of removing pins from the leadframe, the invention extracts the harmful conductive property from the pin surfaces by applying insulating coating. This allows all pins to remain functional while the coated surfaces prevent electrical breakdown, eliminating the need for expensive depopulated leadframe tooling
Solution Approach 2:
The insulating coating is applied as a inexpensive, consumable layer that can be deposited using low-cost printing techniques. This disposable coating approach is far more economical than investing in specialized tooling for depopulated leadframes, while achieving the same electrical isolation effect
3Reliability
If a larger package with greater pin-to-pin pitch is used, then the creepage distance is increased, but the package size and cost increase
Solution Approach 1:
Instead of increasing the physical distance between pins in the horizontal plane, the invention adds insulation in the vertical dimension by applying a coating layer on the pin surfaces. This dimensional approach allows maintaining compact package size while achieving the required creepage distance through the coated surface path
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 method effectively increases the creepage distance, preventing electrical breakdown while reducing costs and improving product development cycles for high voltage IC packages, as it allows for flexible application to various leadframes and substrates.
Implementation Method 1
utilizing polymers or nanomaterials with high dielectric strength for effective insulation
Implementation Method 2
An additive deposition method such as inkjet printing, screen printing, or electrostatic spraying is used to coat a film of insulating ink over one or more external pins
Data Source
AI summary
An integrated circuit (IC) includes a lead frame that has a set of leads coupled to a corresponding set of pins. A semiconductor die with contacts is coupled to the set of leads. Encapsulating material encloses the semiconductor die, such that the set of pins extend beyond the encapsulating material. An additive coating covers one or more of the plurality of pins.