Lead Frame Through Holes for Oxidation Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor device packages with exposed unplated metal leads during singulation are prone to oxidation, which inhibits soldering due to the exposure of unplated metal surfaces between manufacturing and attachment to a system board.
Innovation Solution
Incorporating through hole openings in the leads that are filled with solder wettable materials, such as tin, bismuth, indium, or gold, which are plated before or after encapsulation to prevent oxidation and ensure reliable soldering connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the encapsulant and leads are cut during singulation of the packages, then the packages are separated for individual use, but unplated metal surfaces of the leads are exposed that may oxidize between manufacture and attachment to a system board
Solution Approach 1:
The leads are plated with solder wettable material before singulation occurs. This preliminary plating action ensures that the lead surfaces are protected and maintained in a solder-ready state before the cutting process exposes them, preventing oxidation during the time between manufacturing and attachment.
Solution Approach 2:
A solder wettable material is introduced as an intermediary substance between the unplated metal lead surface and the oxidizing environment. This material layer protects the underlying metal from oxidation while maintaining solderability, acting as a protective barrier during storage and handling.
2Ease of operation
If the leads are exposed at the bottom major side and a side of the package, then external signal and power provision is enabled, but oxidation of exposed metal surfaces inhibits soldering
Solution Approach 1:
The leads have different surface treatments at different locations: the portions requiring external connectivity remain exposed, while the cut surfaces are plated with solder wettable material. This local differentiation ensures both external accessibility and protected soldering surfaces.
Solution Approach 2:
The lead structure combines unplated metal portions (for external connectivity) with plated portions (for protected soldering). This composite approach allows different regions of the same component to have different surface properties optimized for their specific functions.
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 use of solder wettable materials in the through hole openings maintains the leads' solderability, enhancing the strength and reliability of solder joints and extending the operational life by preventing oxidation and ensuring effective attachment to system boards.
Implementation Method 1
the encapsulant and leads are cut during singulation of the packages. However, cutting the leads during the singulation exposes unplated metal surfaces of the leads that may oxidize between manufacture and attachment to a system board
Implementation Method 2
Such oxidation may inhibit soldering
Data Source
AI summary
A method for forming a semiconductor device package includes providing a lead frame array having a plurality of leads. Each of the plurality of leads includes an opening extending through the lead from a first surface of the lead to a second surface of the lead, opposite the first surface, and each of the openings is at least partially filled with a solder wettable material. A plurality of semiconductor devices are attached to the lead frame array. The plurality of semiconductor devices are encapsulated, and, after encapsulating, the plurality of semiconductor devices are separated along separation lines which intersect the openings.