Microwave Overlay Capacitor Fabrication on Printed Circuit Boards
Bibliographic record
Abstract
A technique for making varactors in the form of parallel plate overlay capacitors, using barium strontium titanate (BST): a ferroelectric, polymer composite thick film, has been developed in this work. BST was selected due to the commercial availability of powder. This involves the use of standard air brush techniques to deposit ferroelectric thick films, and planarization of printed circuit boards (PCB) using soldermask to allow for film deposition which was not reported in the literature. A new method to have the PCB prepared appropriately at the manufacturing stage was employed. A bandpass filter on PCB was designed for high frequency measurements and BST composite material electrical characterization. This is due to relative permittivity changing with frequency. The BST composite film recipes were developed using commercial powder and two types of polymer. An existing recipe using cyclic olefin copolymer (COC) was adapted for spray coating, while a new recipe based on poly methyl methacrylate (PMMA) was designed for spray coating. To complete the capacitors, a metal layer was deposited using a Voltera V-One printer with the Elegant Eel conductive ink of thickness 120 𝜇𝑚. Ferroelectric film thicknesses were measured using a Mitutoyo micrometer to be 15−120 𝜇𝑚. Surface profile sweeps were taken with a profilometer as high texture made the profilometer unsuitable for thickness measurements. The capacitor area was measured with a calibrated optical microscope. Low frequency measurements were conducted with a Solartron 1170 Frequency Response Analyzer and were consistent with capacitor theory. High frequency measurements used a TR5048 Vector Network Analyzer (VNA) from Copper Mountain to measure passband characteristics, during which a Sentry 500VA Hipot Tester was used to apply bias to the filters for tunability measurements. The structures were simulated using High Frequency Structure Simulator (HFSS), to provide a relationship between frequency shift and relative permittivity. The relative permittivity of the BST-COC films was 𝜀𝑟=11 at 1.98 𝐺𝐻𝑧, while the BST-PMMA film was 𝜀𝑟=20.5 at 2.09 𝐺𝐻𝑧. The tunability of the films was a 5% relative tuning at 17.5V/ 𝜇𝑚 for BST-PMMA films while the BST-COC films had a 3% tunability at the same field intensity.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".