Semiconductor Lead Recessed Outer End Surface for Solder Adhesion
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Solution Overview
Problem
The existing semiconductor devices face challenges in enhancing mounting reliability, particularly in ensuring that solder adheres to a larger portion of the lead during mounting on a circuit board.
Innovation Solution
A semiconductor device design featuring a lead set with peripheral leads having a recessed outer end surface relative to the sealing resin, where the resin interior top surface connects to the lead outer end surface, and a plating layer with projections to enhance solder adhesion, is implemented. The manufacturing method involves forming a resin body, applying a plating layer, cutting the lead frame, and etching the peripheral leads to create a recessed configuration that promotes better solder bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead outer end surface is flush with the resin end surface, then the manufacturing process is simpler, but the solder adhesion area is limited
Solution Approach 1:
The lead outer end surface is segmented into multiple surfaces including a first outer end surface, a second outer end surface, and a third outer end surface at different heights. This segmentation allows solder to adhere to multiple surfaces, increasing the total adhesion area and improving mounting reliability without significantly complicating the manufacturing process.
Solution Approach 2:
The lead structure transitions from a single-plane flush surface to a multi-level stepped configuration. By creating height differences (z-dimension variations) with the first, second, and third outer end surfaces, the design increases solder contact area in three-dimensional space, enhancing adhesion without requiring additional manufacturing steps beyond standard etching.
2Reliability
If the lead outer end surface is recessed from the resin end surface, then the solder adhesion area increases, but the manufacturing precision requirement increases
Solution Approach 1:
The etching process is applied locally and selectively to specific regions of the lead frame. The first, second, and third outer end surfaces are etched to different depths in specific locations, creating the stepped configuration. This localized etching approach allows for controlled precision in critical areas while maintaining overall manufacturing feasibility.
Solution Approach 2:
The lead frame is first formed with a uniform structure, then the etching process is applied to create the stepped configuration. This preliminary formation of the basic lead structure followed by selective material removal allows for easier control of the final precise dimensions compared to attempting to form the complex shape directly in one step.
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 bonding reliability of the semiconductor device by ensuring solder adheres to a larger area of the peripheral lead, improving the mounting strength and reliability.
Implementation Method 1
a plating layer is formed on a portion of the lead frame that is exposed from the resin body
Implementation Method 2
an etching process is performed to etch away the peripheral lead to a larger extent than the sealing resin and the plating layer
Data Source
AI summary
A semiconductor device includes leads, a semiconductor element and a sealing resin covering the leads and the semiconductor element. The sealing resin includes an obverse surface, a reverse surface, and an end surface between the obverse surface and the reverse surface. The leads include a peripheral lead with a reverse surface exposed from the reverse surface of the resin and with an outer end surface exposed from the end surface of the resin. The outer end surface is located inward from the end surface of the resin. The sealing resin includes an interior top surface connected to its end surface and the outer end surface of the lead. The interior top surface and the reverse surface of the resin face in the same direction.