Base Plate Screw Fixing for PCB Thermal Stress
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Solution Overview
Problem
Electronic devices with smaller and more sophisticated structures experience significant temperature changes, leading to expansion and contraction of printed circuit boards, which applies stress to soldering portions, reducing reliability and potentially causing noise or decreased heat radiation due to screw loosening.
Innovation Solution
The electronic device incorporates a base plate with through-holes and a housing with screw holes, where screw members are inserted to fix the base plate, and two projections are formed at symmetric points relative to the screw hole center to distribute rotational forces evenly, canceling them out and allowing the base plate to move while maintaining secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fastening force of the screw member is reduced to allow the printed circuit board to move in its surface direction, then the stress applied to the soldering portion is decreased, but the screw member may be loosened by the stress generated by expansion and contraction of the printed circuit board
Solution Approach 1:
The support structure is segmented into multiple supporting pillars distributed across the housing, with each pillar providing localized support at specific positions. This segmentation allows the printed circuit board to move freely in the surface direction while preventing screw loosening through distributed support points that counteract expansion and contraction stresses.
Solution Approach 2:
The supporting pillars extend in the thickness direction of the printed circuit board, providing support from the housing to the board. This vertical dimensionality allows the board to move horizontally in the surface direction while the pillars prevent vertical loosening of screws, effectively separating the movement freedom in one dimension from the constraint in another.
2Reliability
If the fastening force of the screw member is reduced to allow the printed circuit board to move, then stress on soldering portions is decreased, but noise may be generated due to movement or vibration of the printed circuit board within the housing
Solution Approach 1:
Multiple supporting pillars are distributed at specific positions across the housing to provide localized support points. This segmentation allows controlled movement at non-supported areas while preventing excessive vibration and noise through strategically placed support structures that dampen oscillations without restricting necessary thermal expansion movement.
3Reliability
If the fastening force of the screw member is reduced to allow the printed circuit board to move, then stress on soldering portions is decreased, but heat radiating performance may be decreased due to a change of relative position between the printed circuit board and the housing
Solution Approach 1:
The supporting pillars provide vertical support in the thickness direction while allowing horizontal movement in the surface direction. This dimensional separation enables the printed circuit board to maintain optimal thermal contact with the housing for heat radiation while simultaneously allowing the movement necessary to reduce stress on soldering portions during thermal expansion and contraction.
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 solution reduces torque on screw members, minimizing stress on soldering portions and preventing loosening, thus enhancing the reliability of electrical connections and maintaining heat radiation performance during temperature changes.
Implementation Method 1
a torque for screwing the screw member is reduced so as to decrease a fastening force of the screw member. Then, it becomes possible that the printed circuit board moves in a surface direction thereof
Implementation Method 2
A temperature change inside of a housing of the electronic device becomes relatively larger as a result of such a smaller-sized and more-sophisticated structure of the electronic device. Accordingly, expansion and/or contraction of a printed circuit board have become a problem.
Data Source
AI summary
A base plate for a circuit board assembly, to which an electronic component is soldered, has a through-hole. A screw hole is formed in a housing, to which the base plate is fixed by screw members. Multiple screw-fixing portions are formed in an electronic device, so that each of the screw members is inserted through each of the through-holes of the base plate and fixed to the housing in each of the screw-fixing portions. Two projections are formed at a first casing of the housing in each of the screw-fixing portions, so that the base plate is in contact with the first casing at two contacting points formed by the projections. The projections are symmetrically formed with respect to a center of the screw hole.