Interface Unit Mitigates Connector Warping via CTE Matching
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Solution Overview
Problem
The mismatch in coefficients of thermal expansion (CTE) between connectors and printed circuit boards (PCBs) during the solder re-flow process leads to stress, warpage, and reliability issues, causing fractures in solder connections and mechanical/electrical problems.
Innovation Solution
An interface unit with a coefficient of thermal expansion that complements the CTE of the substrate and connector materials is used to maintain alignment and mitigate stress by selecting a material with a second CTE that matches the expansion/contraction rates of the substrate, ensuring compatible thermal expansion and contraction during heating and cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If connectors and PCBs are directly connected without interface compensation, then device complexity is reduced, but stress on solder joints increases due to CTE mismatch during thermal events
Solution Approach 1:
An interface unit with complementary CTE is introduced between the connector and PCB. This intermediary component absorbs differential thermal expansion stresses during solder re-flow and operational thermal events, protecting solder joints from fracture while maintaining a relatively simple overall structure.
Solution Approach 2:
The interface unit is designed with specific material properties (complementary CTE) that change in response to thermal events. By selecting materials with appropriate thermal expansion characteristics, the interface unit dynamically adjusts its dimensional changes to compensate for CTE mismatch between connector and PCB.
2Ease of manufacture
If connectors and PCBs are directly connected, then manufacturing process is simplified, but warpage of connector and PCB occurs during cooling phase of solder re-flow
Solution Approach 1:
The interface unit serves as a mediator that maintains alignment between connector and PCB during the cooling phase. By positioning the interface unit between these components, it compensates for differential contraction, preventing warpage and maintaining manufacturing precision without complicating the assembly process.
Solution Approach 2:
The interface unit is designed to preemptively counteract the warping forces that occur during cooling. Its complementary CTE creates a preliminary counter-balancing effect that prevents alignment deviations before they can cause manufacturing defects.
3Ease of manufacture
If connector material with high CTE is used, then ease of manufacture is improved, but connector warping occurs that lifts connector contacts causing missing solder connections
Solution Approach 1:
The interface unit acts as a mediator between the high-CTE connector and the substrate, absorbing the differential expansion forces. This allows the use of easily manufactured connector materials while preventing contact lifting and maintaining precise alignment for reliable solder connections.
4Device complexity
If connector remains warped after assembly, then device complexity is reduced, but plugging issues occur since plug will not seat fully into connector
Solution Approach 1:
The interface unit prevents connector warping that would otherwise interfere with plug insertion. By maintaining connector flatness and alignment through thermal event compensation, it ensures proper plugging functionality without adding significant structural complexity.
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
The complementary CTE interface unit effectively reduces warping, maintains alignment, and minimizes stress on solder joints, enhancing the mechanical and electrical properties of component packaging by synchronizing the thermal expansion of connectors and substrates.
Implementation Method 1
Both the body and the substrate have a coefficient of thermal expansion (CTE) that is inherently associated with their material or material composition. The interface material is selected so that the second CTE complements the third CTE.
Data Source
AI summary
Embodiments of the disclosure relate to an apparatus and method for mitigation of warping of assembly components when subject to a thermal event. An interface unit with a complementary coefficient of thermal expansion is embodied in the assembly. The interface unit is configured to be received by a connector joined to the assembly substrate. The interface unit has a coefficient of thermal expansion (CTE) that complements the CTE of the assembly components in order to maintain the connector in alignment with the substrate and enable the connector to expand or contract with the substrate when subject to the thermal event.