Semiconductor Package Wettable Flanks Using Through-Hole Electroplating
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Solution Overview
Problem
Existing semiconductor package manufacturing processes face challenges in achieving optimal solder wetting on lead flanks due to insufficient thickness of electroless deposition, leading to incomplete coverage and the need for additional processing steps like dry packing to maintain solder wettability, which increases costs and reduces manufacturing efficiency.
Innovation Solution
The implementation of a substrate with through holes that form wettable flanks by electroplating exposed edges of leads, allowing for thicker solder wettable material application and eliminating the need for electroless plating and dry packing, thereby enhancing solder wetting and bond reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electroless deposition is used to apply solder wettable material to lead flanks, then some coverage is achieved, but the thickness is insufficient and coverage is incomplete
Solution Approach 1:
The lead structure is segmented by introducing through-holes that create distinct regions: the original flank surface and the newly exposed internal edges. This segmentation allows different plating methods to be applied to different segments - electroless plating on the original surface and electroplating on the exposed edges - thereby achieving both complete coverage and sufficient thickness that were not possible with a single uniform approach
Solution Approach 2:
The invention transitions from a two-dimensional surface coating problem to a three-dimensional solution by creating through-holes that expose internal edges. This dimensional change creates new surfaces that can be selectively plated, allowing the solder wettable material to be applied not just on the external flank surface but also on the internally exposed edges, ensuring complete coverage and adequate thickness
2Reliability
If electroless plating is used to maintain solder wettability, then solder wetting is achieved, but additional processing steps like dry packing are required
Solution Approach 1:
The through-holes are created and internal edges are exposed before the final soldering process, allowing electroplating to be applied in advance to create a robust solder wettable surface. This preliminary action ensures that the solder wetting capability is established before the package is sealed, eliminating the need for subsequent dry packing steps to maintain wettability
Solution Approach 2:
The invention extracts the critical function of creating solder wettable surfaces from the constrained electroless plating process and relocates it to the more versatile electroplating process. By taking out the surface preparation function and applying it through a different mechanism (electroplating on exposed edges), the need for additional protective processing steps like dry packing is eliminated
3Manufacturing precision
If through holes with reentrant openings are created in the substrate, then wettable flanks are formed with complete coverage, but the substrate structure becomes more complex
Solution Approach 1:
The through-holes are not uniformly distributed but are strategically positioned only where leads require enhanced solder wetting. The reentrant openings are created locally at specific positions along the lead flanks, providing targeted improvement rather than uniform structural modification. This local application of complexity minimizes the overall impact on substrate design while achieving complete coverage where needed
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 approach ensures complete flank coverage with a desired thickness of solder wettable material, improving bond visibility and reliability, reducing processing steps, and increasing manufacturing efficiency and yield.
Implementation Method 1
The first set of edges of the first set of spaced apart through holes may extend from the electrically insulating material. The second set of edges of the second set of spaced apart through holes may extend from the electrically insulating material. The first set of edges may form a first set of wettable flanks for the first plurality of leads. The second set of edges may form a second set of wettable flanks for the second plurality of leads.
Data Source
AI summary
Implementations of a substrate may include a first side coupled with a first plurality of leads, the first side including a first set of spaced apart through holes therein; and a second side coupled with a second plurality of leads, the second side including a second set of spaced apart through holes therein. The first side may oppose the second side where a portion of a first set of edges of the first set of spaced apart through holes form a first set of wettable flanks for the first plurality of leads; and a portion of a second set of edges of the second set of spaced apart through holes form a second set of wettable flanks for the second plurality of leads.