Leadless Package System With T-Shaped Contact Terminals
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Solution Overview
Problem
Conventional IC packages face challenges in achieving high functionality, reliability, and manufacturing robustness due to contact failures and delamination issues between IC packages and printed circuit boards, particularly in miniaturized devices where high circuit speeds and reduced package thickness are required.
Innovation Solution
A leadless package system is developed, featuring an integrated circuit die with contact pads, external contact terminals with a conductive and external coating layer, and an encapsulant that encapsulates both, with T-shaped profiles on the terminals and pads to enhance adhesion and mechanical strength, and extensions of the coating layer for improved solder joint wetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If leadless packages with high density of contact terminals are used to decrease package footprint and increase functionality, then package functionality and integration density are improved, but contact terminal delamination and signal degradation occur due to poor contacts between IC package and printed circuit board
Solution Approach 1:
The contact terminal is divided into multiple functional layers: a conductive layer for electrical connection, an external coating layer for solderability and protection, and an encapsulant for mechanical support. This segmentation allows each layer to optimize its specific function while working together to prevent delamination and improve overall contact reliability
Solution Approach 2:
The contact terminal uses a composite structure combining different materials: copper or aluminum for the conductive layer, tin or lead-based coatings for the external layer, and epoxy or polymer encapsulant. This composite approach provides electrical conductivity, solderability, and mechanical strength simultaneously, resolving the contradiction between high density and reliability
2Length of stationary object
If package thickness is reduced to meet miniaturization requirements, then device size is improved, but mechanical strength and structural integrity of the package are compromised
Solution Approach 1:
The encapsulant is formulated as a thin-film composite material that provides flexible mechanical support. This thin encapsulant layer maintains package integrity while allowing the overall package thickness to be reduced for miniaturization applications
Solution Approach 2:
The contact terminals extend below the encapsulant surface in a vertical dimension, creating protruding contact surfaces. This dimensional extension compensates for reduced thickness by providing additional mechanical strength and solder joint area in the vertical direction, maintaining structural integrity despite thinner overall package
3Ease of manufacture
If conventional molding processes are used to encapsulate IC die and leads, then manufacturing simplicity is maintained, but external contact terminals lack proper adhesion and solderability
Solution Approach 1:
The conductive and external coating layers are deposited on the contact terminals before the encapsulation process. This preliminary coating ensures that the terminals have proper adhesion and solderability properties before being enclosed, while the subsequent encapsulation step remains a simple molding process that protects these pre-prepared surfaces
Data Source
AI summary
A leadless package system includes: an integrated circuit die having contact pads; external contact terminals with a conductive layer and an external coating layer; connections between contact pads in the integrated circuit die and the external contact terminals; and an encapsulant encapsulates the integrated circuit die and the external contact terminals including the external coating layer.