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PCB High Frequency Board Board Selection and Production Processing

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Circuit board production of high frequency board definition high frequency board refers to the electromagnetic frequency of the higher special circuit boards for high frequency (frequency greater than 300MHZ or wavelength of less than 1 meter) and microwave (frequency greater than 3GHZ or wavelength of less than 0.1 meters) in the field of PCB, is in the microwave substrate copper cladding board on the use of ordinary rigid circuit board manufacturing method of some of the processes or the use of special treatment methods to produce the circuit board. Generally speaking, high frequency board can be defined as the frequency of 1GHz or more circuit boards.

With the rapid development of science and technology, more and more equipment design is in the microwave band (> 1GHZ) or even with the millimeter wave field (30GHZ) above the application, which also means that the frequency is getting higher and higher, the substrate of the circuit board requirements are also getting higher and higher. For example, the substrate material needs to have excellent electrical properties, good chemical stability, with the increase in the frequency of the power signal in the substrate loss requirements are very small, so the importance of high-frequency boards came to the fore.

PCB high frequency board applications Mobile communication products; amplifiers, low noise amplifiers, etc.; power splitters, couplers and couplers, duplexers, filters and other passive components; automotive collision avoidance systems, satellite systems, radio systems and other fields, electronic equipment, high frequency is the development trend.

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Classification of high frequency board powder ceramic filled thermosetting materials:

A. Manufacturer.

4350B/4003C from Rogers Corp;

Arlon's 25N/25FR;

Taconic's TLG series.

B. Processing Method.

Similar process with epoxy resin/glass woven fabric (FR4), except that the sheet is more brittle and easy to break the plate, and the life span of drilling nozzles and gong knives when drilling and gonging the plate should be reduced by 20%, PTFE (polytetrafluoroethylene) material.

A. Manufacturer:

RO3000 series, RT series, TMM series of Rogers Inc;

Arlon's AD/AR series, IsoClad series, CuClad series;

Taconic's RF series, TLX series, TLY series;

F4B, F4BM, F4BK, TP-2 of Taconic Microwave.

B. Processing Method: 

a, Opening: Must retain the protective film to open the material to prevent scratches and indentations

b, Drilling

 a) Use brand new drilling nozzle (standard 130), one piece of one stack is the best, pressure foot pressure is 40psi.

 b) Aluminum sheet for the cover, and then use 1mm milamine pads, the PTFE plate to tighten the

 c) After drilling, use an air gun to blow out the dust in the hole.

 d) Use the most stable drilling machine, drilling parameters (basically the smaller the hole, the faster the drilling speed, the smaller the Chip load, the lower the return speed).

c, Hole Treatment

Plasma treatment or sodium naphthalene activation treatment is conducive to hole metallization.

d, PTH Copper Sinking

 a, After micro-etching (micro-etching rate of 20 micro-inch control), in the PTH pulling from the oil cylinder to start into the plate.

 b, If necessary, then the second PTH, only from the expected? Cylinders start to feed the plate.

e. Solder Resist

 a) Pre-treatment: Acid wash, no mechanical grinding.

 b) Bake the board after pre-treatment (90℃, 30min), brush with green oil for curing.

 c) Three sections of the baking plate: a section of 80 ℃, 100 ℃, 150 ℃, the time of 30min (if you find that the substrate surface dumping oil, you can rework: wash off the green oil, re-activation of the treatment).

f, Gong Plate

The white paper will be laid in the PTFE board line surface, the top and bottom with a thickness of 1.0MM etched copper FR-4 substrate plate or phenolic base plate clamping, as shown in Figure: high-frequency board gong plate stacking method.

After the gong plate plate edge burrs need to be carefully scraped by hand to prevent damage to the substrate and copper surface, and then separated by a considerable size of sulfur-free paper, and visual inspection to reduce burrs, focusing on the gong plate process to Shaw the effect should be good. 

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C. Process Flow NPTH PTFE Board Processing Flow

Cutting -drilling- dry film - inspection - etching - etching inspection - solder resist - character - tin spray - molding - testing - final inspection - packaging - shipping.

D. PTH PTFE Board Processing Flow

Cutting - Drilling - Hole treatment (plasma treatment or sodium naphthalene activation treatment) - Copper immersion - Plate electrodes - Dry film - Inspection - Graphic electrodes -Etching- Etching inspection - Soldermask - Characters - Spraying tin - Molding -Testing- Final inspection - Packaging - Shipping.

E. Summarize The Difficulties of High Frequency Board Processing

 a, Copper immersion: the hole wall is not easy to copper;

 b, Figure turn, etching, line width of the line notch, sand hole control;

 c, Green oil process: green oil adhesion, green oil blistering control;

 d, Each process appears to strictly control the board surface scratches.

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