Flat No-Lead Package Wettable Sidewall for Reliable Lead Coupling
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Solution Overview
Problem
Existing flat no-lead semiconductor packages face challenges in providing reliable surface-mounted structures with exposed leads for efficient electrical connections, as they often rely on flat surfaces which may not offer sufficient contact area or reliability for coupling with other components.
Innovation Solution
The implementation of a surface-mounted structure with recessed members on the end portions of the leads, allowing for a wettable sidewall for enhanced coupling with exposed leads, utilizing a coupling medium such as solder paste or adhesive for secure electrical connections between the semiconductor die and the leadframe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat surface is used for coupling the surface mounted structure to the exposed lead, then the manufacturing process is simple, but the contact area is insufficient and connection reliability is reduced
Solution Approach 1:
The end portion of the surface mounted structure transitions from a two-dimensional flat surface to a three-dimensional structure with a recessed member. This recessed member creates a cavity that receives coupling medium, forming a wettable sidewall that extends vertically. This dimensional change increases the contact area between the surface mounted structure and the exposed lead, thereby improving connection reliability while maintaining manufacturing simplicity.
2Reliability
If a recessed member is added to create a wettable sidewall, then the contact area and coupling reliability are improved, but the manufacturing complexity increases
Solution Approach 1:
The recessed member is formed with a curved or rounded bottom surface rather than a sharp corner, creating a smooth transition for the coupling medium. This curvature allows the coupling medium to evenly distribute and wet the sidewall surface, improving adhesion and coupling reliability. The curved geometry is easily formed using standard molding or machining processes, minimizing the impact on manufacturing complexity.
3Manufacturing precision
If the end portion includes only a flat surface, then the device complexity is low, but the soldering or adhesive bonding quality is insufficient
Solution Approach 1:
The end portion of the surface mounted structure features a localized recessed member with a wettable sidewall, while the rest of the structure maintains its original simple geometry. This localized modification concentrates the bonding functionality in a specific area where it is most needed, improving soldering or adhesive bonding quality without requiring complex changes to the entire device structure.
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 configuration enhances the reliability and versatility of electrical connections by providing a larger contact area through the recessed members, enabling better soldering or adhesive bonding, thus improving the overall performance and connectivity of the semiconductor package.
Implementation Method 1
an end portion may include a recessed member so that a coupling medium may be received in the recessed member and so that in addition to or instead of a flat surface for the coupling, the end portion of the surface mounted structure also includes a wettable side wall for the coupling to the exposed lead
Data Source
AI summary
The present disclosure is directed to a flat no-lead semiconductor package with a surfaced mounted structure. An end portion of the surface mounted structure includes a recessed member so that the surface mounted structure is coupled to leads of the flat no-lead semiconductor package through, among others, the sidewalls of the recessed members.