Lead-Frame Package Lead Structure for Thermal Stress Relief
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Solution Overview
Problem
Existing lead-frame packages face challenges in maintaining reliable electrical connections under temperature changes, particularly in harsh environments, due to stress on solder joints caused by expansion and compression of components, and inefficient manufacturing processes.
Innovation Solution
The development of a lead-frame package with vertically bent conductive leads and recesses, featuring a solder wettable surface exposed laterally and insulated from the die pad, allowing for greater flexibility and resilience to thermal expansion, combined with a manufacturing process using strip panel molding for efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lead-frame package structures are used, then manufacturing processes are simpler, but electrical connections become unreliable under temperature changes due to stress on solder joints
Solution Approach 1:
The conductive lead is divided into multiple segments including a first portion, a second portion, and a connecting portion. This segmentation allows each segment to independently accommodate thermal expansion and compression, reducing stress on solder joints while maintaining electrical connection reliability.
Solution Approach 2:
The lead structure incorporates dynamic flexibility through its multi-portion design, enabling the lead to flex and adapt to thermal expansion and compression of the semiconductor IC during temperature changes, thereby maintaining reliable electrical connections.
2Reliability
If conductive leads are extended beyond package perimeter, then solder joint reliability improves, but manufacturing precision requirements increase
Solution Approach 1:
The conductive lead is divided into multiple portions with distinct functions: the first portion provides structural support, the second portion extends beyond the package perimeter for soldering, and the connecting portion flexibly connects them. This segmentation simplifies manufacturing by allowing each portion to be optimized independently.
Solution Approach 2:
Different portions of the conductive lead have different structural characteristics optimized for their specific functions. The distal end features a solder wettable surface with specific geometry for reliable soldering, while other portions have structures optimized for flexibility and stress distribution.
3Object-affected harmful factors
If molding material completely encloses semiconductor IC, then environmental protection improves, but thermal dissipation efficiency decreases
Solution Approach 1:
The molding material forms a protective enclosure around the semiconductor IC while incorporating flexible lead structures that can accommodate thermal expansion. The lead structure acts as a thermal pathway, allowing heat to conduct from the IC through the lead to the PCB, maintaining both protection and thermal dissipation.
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 design enhances the reliability of semiconductor ICs by ensuring durable electrical connections and reduces the package's footprint, while improving manufacturing efficiency and flexibility, especially in extreme conditions.
Implementation Method 1
a solder wettable surface of the conductive lead is exposed in a lateral direction
Data Source
AI summary
An example lead-frame package, a method of manufacturing a lead-frame package, and an electrical system comprising a lead-frame package with improved conductive lead structure are provided. An example lead-frame package includes a semiconductor IC thermally coupled to a die pad. Molding material encloses the semiconductor IC defining a perimeter of the lead-frame package. A conductive lead is electrically connected to the semiconductor IC and exposed at a surface of the lead-frame package, the conductive lead having a proximal end and a distal end. The distal end of the conductive lead extends beyond the perimeter of the lead-frame package, the distal end bent vertically such that a solder wettable surface of the conductive lead is exposed in a lateral direction. The molding material further insulates the conductive lead from the die pad. A conductive lead recess is defined between the proximal end of the conductive lead and the die pad.