What is PCB high frequency board?
Changsha high-frequency board refers to a special circuit board with high electromagnetic frequency, which is used for PCB in high-frequency (frequency greater than 300MHZ or wavelength less than 1m) and microwave (frequency greater than 3GHZ or wavelength less than 0.1m) fields. It is a circuit board produced by using part of the manufacturing process of common rigid circuit board or special treatment method on microwave base copper clad laminate. Generally, high frequency board can be defined as circuit board with frequency above 1GHz. With the rapid development of science and technology, more and more equipment designs are applied in the microwave frequency band (> 1 GHz) or even in the millimeter wave field (30GHZ), which also means that the frequency is getting higher and higher, and the requirements for the substrate of the circuit board are getting higher and higher. For example, the substrate material needs to have excellent electrical properties and good chemical stability, and the loss requirement on the substrate is very small with the increase of power signal frequency, so the importance of high-frequency plate is highlighted.
Application field of high frequency board: mobile communication products; Power amplifier, low noise amplifier, etc. Passive devices such as power divider, coupler, duplexer and filter; In the fields of automobile anti-collision system, satellite system, radio system, etc., the high frequency of electronic equipment is the development trend.
Classification of high frequency boards
Ceramic filled thermosetting material
A. manufacturer:
Rogers company 4350B/4003C
25N/25FR from Arlon Company
Taconic company’s TLG series
B, processing method:
The processing flow is similar to that of epoxy resin/glass woven cloth (FR4), except that the board is brittle and easy to break, and the service life of drill and gong will be reduced by 20% when drilling and gong boards.
PTFE (polytetrafluoroethylene) material
A. manufacturer:
RO3000 series, RT series and TMM series of Rogers Company
Arlon’s AD/AR series, IsoClad series and CuClad series
Taconic’s RF series, TLX series and TLY series
F4B, F4BM, F4BK and TP-2 of Taixing Microwave
B, Changsha PCB high frequency board processing method:
1. Cutting: the protective film must be kept for cutting to prevent scratches and indentations.
2. Drill holes. 1. Use brand-new drill nozzles (standard 130), one by one is the best, the presser foot pressure is 40psi 2, the aluminum sheet is the cover plate, and then use 1mm melamine backing plate to tighten the PTFE sheet.
3. Blow out the dust in the hole with an air gun after drilling.
4. Use the most stable drilling rig, drilling parameters (basically, the smaller the hole is, the faster the drilling speed is, the smaller the Chip load is, the smaller the return speed is) 3. Hole treatment, plasma treatment or sodium naphthalene activation treatment is beneficial to hole metallization 4. After PTH copper deposition 1 is slightly etched (the micro-etching rate has been controlled by 20 micro-inches), start to feed the plate 2 from the oil removal cylinder in PTH. If necessary, pass the second PTH, just as expected? Cylinder start feeding plate
5. Solder resistance: 1 Pretreatment: the plate is washed with acid, but the plate is not baked with mechanical grinding (90℃, 30min) after pretreatment. Brush green oil to cure the plate in three sections: one section is 80℃, 100℃, 150℃, and the time is 30min each (if oil is thrown on the substrate surface, it can be reworked: turn green.
6. Gong board: Lay white paper on the circuit surface of PTFE board, and clamp it with FR-4 substrate board or phenolic bottom board with a thickness of 1.0MM etched to remove copper, as shown in the figure:
High-frequency board-gong-board lamination method The burrs on the back board edge of the gong board need to be carefully shaved by hand to prevent damage to the base material and copper surface, and then separated by sulfur-free paper of equivalent size, and visually detected. To reduce burrs, the key point is that the effect of removing burrs in the gong board process should be good.
High frequency plate process
NPTH PTFE plate processing flow
Processing flow of PTFE plate for PTH
summary
Difficulties in high frequency plate processing
1. Copper deposition: the hole wall is not easily plated with copper.
2. Control of drawing, etching, line gap of line width and Chacon.
3. Green oil process: control of green oil adhesion and foaming.
4. Strictly control the scratch of board surface in each process.
