PCB Planar Transformer Windings With Self-Aligned Core Leg Setback
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Solution Overview
Problem
Conventional PCB fabrication techniques introduce manufacturing tolerances that lead to variations in conductive features, winding positions, and core leg placements, resulting in reduced efficiency and increased losses in planar transformers due to larger apertures and setbacks, which compromise the magnetic flux density and core leg diameters.
Innovation Solution
The implementation of self-aligned windings and core legs, where apertures are formed after the winding features are established, and the use of etching to create a setback between the windings and core legs, allowing for improved alignment and reduced tolerances, enabling larger core legs and wider winding traces to minimize transformer losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional PCB fabrication techniques are used, then manufacturing is easier and more standard, but cumulative manufacturing tolerances increase leading to larger apertures and setbacks
Solution Approach 1:
The patent inverts the conventional sequence by forming apertures after creating the winding features, rather than forming apertures before. This reversal allows the aperture positions to be precisely aligned to the already-established winding features, eliminating cumulative tolerances and enabling the inner edges of windings to overlap the aperture edges without requiring additional setback.
Solution Approach 2:
The methodology employs self-aligned windings where the aperture formation process automatically positions itself relative to the pre-formed winding features. The etching or drilling of apertures is performed after the windings are complete, allowing the aperture edges to naturally align with the winding inner edges, creating a self-correcting alignment system that eliminates the need for complex tolerance compensation.
2Reliability
If larger apertures and setbacks are used to accommodate tolerances, then manufacturing is more robust, but magnetic flux density decreases and transformer losses increase
Solution Approach 1:
By inverting the fabrication sequence to form apertures after windings, the patent eliminates the need for oversized apertures and setbacks that were previously required to accommodate cumulative tolerances. This results in smaller aperture openings that maintain tighter magnetic flux density while still achieving reliable assembly through the self-aligned approach.
3Loss of energy
If tighter tolerances are applied to reduce setbacks, then transformer efficiency improves, but manufacturing difficulty increases
Solution Approach 1:
The patent achieves tight effective tolerances by inverting the fabrication sequence. Instead of applying tight tolerances to aperture positioning relative to windings (which would increase manufacturing difficulty), the method forms windings first and then apertures, making the aperture formation the reference operation. This eliminates cumulative tolerances and achieves tight effective tolerances without increasing fabrication difficulty.
Data Source
AI summary
Electrical/magnetic components and methods of making such components are provided. One method includes providing a multilayer printed circuit board (PCB) including conductive features arranged on conductive layers of the PCB to form one or more windings around one or more predetermined axes. The method further includes forming a hole in the PCB at each of the one or more predetermined axes to accommodate one or more core legs. For each hole, an inner edge of one of the windings overlaps an edge of the hole in a lateral direction after the hole is formed. The method further includes assembling a magnetically permeable core including the one or more core legs, each core leg extending into one of the holes at the one or more predetermined axes.