PCB Fabrication

PCB high-frequency board selection and production and processing methods-

by:A-TECH      2021-04-05
PCB high-frequency board selection and production and processing methodsRelease time: 2018-03-08 0 Definition of high-frequency board production of circuit boards High-frequency boards refer to special circuit boards with higher electromagnetic frequencies for high frequencies (frequency greater than 300MHZ Or the wavelength is less than 1 meter) and microwave (frequency greater than 3GHZ or wavelength less than 0.1 meter) PCB is a circuit board produced by using part of the process of ordinary rigid circuit board manufacturing method on microwave substrate copper clad laminate or using special processing methods . Generally speaking, a high-frequency board can be defined as a circuit board with a frequency above 1GHz! With the rapid development of science and technology, more and more equipment is designed for applications in the microwave frequency band (>1GHZ) and even in the millimeter wave field (30GHZ). This also means that the frequency is getting higher and higher, and the circuit board is The requirements for materials are getting higher and higher. For example, the substrate material needs to have excellent electrical properties, good chemical stability, and the loss on the substrate with the increase of the power signal frequency is very small, so the importance of the high-frequency board is highlighted. 2. PCB high-frequency board application fields: mobile communication products; power amplifiers, low-noise amplifiers, etc.; passive components such as power splitters, couplers, duplexers, filters, etc.; automotive anti-collision systems, satellite systems, radio systems, and other fields, The high frequency of electronic equipment is the development trend. 2. PCB high-frequency board application fields: mobile communication products; power amplifiers, low-noise amplifiers, etc.; passive components such as power splitters, couplers, duplexers, filters, etc.; automotive anti-collision systems, satellite systems, radio systems, and other fields, The high frequency of electronic equipment is the development trend. Classification of high-frequency boards: Powder ceramic filled thermosetting material A, manufacturer: Rogers' 4350B/4003C Arlon's 25N/25FR Taconic's TLG series B, processing method: similar to epoxy resin/glass woven cloth (FR4) The processing flow is that the plate is relatively brittle and easy to break. The life of the drill tip and gong knife should be reduced by 20% when drilling and gong plate. PTFE (polytetrafluoroethylene) material A. Manufacturer: Rogers' RO3000 series, RT series, TMM series, Arlon's AD/AR series, IsoClad series, CuClad series, Taconic's RF series, TLX series, TLY series Taixing Microwave F4B, F4BM, F4BK, TP-2 B, processing methods: 1. Cutting: the protective film must be kept to prevent scratches and indentation 2. Drilling 1. Use a brand new drill (standard 130), one piece by piece Stacking is the best, the pressure of the presser foot is 40psi 2. The aluminum sheet is the cover plate, and then the 1mm melamine backing plate is used to tighten the PTFE plate 3. After drilling, use the air gun to blow the dust out of the hole 4. Use the most stable drilling machine. Drilling parameters (basically the smaller the hole, the faster the drilling speed, the smaller the Chip load, the smaller the return speed) 3. Hole treatment Plasma treatment or sodium naphthalene activation treatment is conducive to hole metallization 4. PTH sinking copper 1 after micro-etching (Controlled by 20 microinches with a micro-erosion rate), when the PTH pulls the plate from the de-oil tank, 2 If necessary, pass the second PTH, just start the plate from the expected cylinder 5. Solder mask 1 Pre-treatment: Adopt Acid washing plate, can’t use mechanical grinding plate 2 Pre-treatment and baking plate (90℃, 30min), brush green oil and solidify 3 stages baking plate: one stage 80℃, 100℃, 150℃, time 30min each (if found Oil on the substrate surface can be reworked: wash off the green oil and reactivate it) 6. Lay white paper on the circuit surface of the PTFE board on the gong board, and use the FR-4 substrate board with a thickness of 1.0MM to etch away the copper or The phenolic bottom plate is clamped, as shown in the figure: High-frequency plate gong plate stacking method The back plate edge of the gong plate needs to be carefully scraped by hand to prevent damage to the substrate and copper surface, and then separated with a considerable size of sulfur-free paper, and visually inspected , To reduce burrs, the key point is that the gong board process has a good effect. Four process flow NPTH's PTFE board processing flow: cutting-drilling-dry film-inspection-etching-etching-soldering-resist-character-spraying-molding-testing-final inspection-packaging-shipping PTH's PTFE board processing flow Cutting-drilling-hole treatment (plasma treatment or sodium naphthalene activation treatment)-copper immersion-board electricity-dry film-inspection-diagram electricity-etching-corrosion inspection-solder mask-character-spray tin-forming-test-final Inspection-Packaging-Shipment Five Summary of Difficulties in High-frequency Board Processing 1. Copper Immersion: The hole wall is not easy to be copper 2. Diagram transfer, etching, line width line gap, sand hole control 3. Green oil process: Green oil adhesion , Green oil foaming control 4. Strict control of scratches on the surface of each process.
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