Let's take a look at the production proofing of high-frequency circuit boards

definition

High frequency circuit board refers to a special circuit board with high electromagnetic frequency, which is used for PCB in the field of high frequency (frequency greater than 300 MHz or wavelength less than 1 m) and microwave (frequency greater than 3 GHz or wavelength less than 0.1 m). It is a circuit board produced on the microwave substrate copper clad plate by using part of the process of the common rigid circuit board manufacturing method or using special processing methods. Generally speaking, it can be defined as a circuit board with a frequency above 1GHz!

With the rapid development of science and technology, more and more devices are 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 requirements for the substrate of the circuit board are getting higher and higher. For example, materials need to have excellent electrical properties, good chemical stability, and the loss on the substrate with the increase of power signal frequency is very small, so the importance of high-frequency plates is highlighted. 2 Mobile

 communication products in the application field of PCB high frequency boards; Power amplifier, low noise amplifier, etc; Power divider, coupler, duplexer, filter and other passive components; High frequency electronic equipment is the development trend in automotive anti-collision system, satellite system, radio system and other fields.

Mobile communication products in PCB high-frequency circuit board application field; Power amplifier, low noise amplifier, etc; Power divider, coupler, duplexer, filter and other passive components; High frequency electronic equipment is the development trend in automotive anti-collision system, satellite system, radio system and other fields.

Classification of high frequency boards Powder ceramic filled thermosetting materials

A、:

4350B/4003C of Rogers

Arlon's 25N/25FR

Taconic TLG Series

B. Processing method of circuit board:

The processing process is similar to that of epoxy resin/glass woven fabric (FR4), except that the plate is relatively brittle and easy to break. The life of the drill tip and the gong knife will be reduced by 20% when drilling holes and gongs. PTFE (polytetrafluoroethylene) material

A. PCB manufacturer: RO3000 series, RT series and TMM series of Rogers

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

Taconic's RF series, TLX series, TLY series

F4B, F4BM, F4BK, TP-2 of Taixing Microwave

B. Processing method: 1. Cutting: the protective film must be kept to prevent scratches and indentation

High frequency circuit board

2. Circuit board drilling

1. Use a new drill bit (standard 130), one piece for one stack is the best, and the pressure of the presser foot is 40psi

2. The aluminum sheet is the cover plate, and then use 1mm melamine backing plate to tighten the PTFE plate

3. Blow out the dust in the hole with air gun after drilling

4. With the most stable drilling rig, drilling parameters (basically, the smaller the hole, the faster the drilling speed, the smaller the chip load, the smaller the return speed)

3. Hole processing of circuit board

Plasma treatment or sodium naphthalene activation treatment is conducive to pore metallization

4. Circuit board PTH copper plating

1 After micro etching (the micro etching rate is controlled by 20 micro inches), pull at PTH to enter the plate from the oil cylinder

2. If necessary, after the second PTH, it is only necessary to start from the estimated? Cylinder starts to enter the plate

5. Soldering resistance of circuit board

1. Pretreatment: acid washing is used instead of mechanical grinding

2. Baked plate after pretreatment (90 ℃, 30min), painted with green oil for curing

Three sections of baking board: one section at 80 ℃, 100 ℃, 150 ℃, 30 min each (if the substrate surface is found to shed oil, it can be reworked: wash the green oil and reactivate it)

6. Circuit board gongs

Lay the white paper on the PTFE board line pavement, and clamp it up and down with FR-4 base material plate or phenolic base plate with 1.0mm thick etched copper removal, as shown in the figure: high-frequency plate, gongs and plates lamination method

The rough edges on the back edge of the gongs need to be carefully trimmed by hand to prevent damage to the base material and copper surface. They should be separated by sulfur free paper of appropriate size and visually inspected. Burrs should be reduced. The key point is that the gongs should be removed effectively during the process.

PCB process flow NPTH's PTFE board processing flow

Cutting - drilling - dry film - inspection - etching - corrosion inspection - solder resistance - characters - tin spraying - forming - testing - final inspection - packaging - shipping

Process flow of PTFE plate of PTH

Cutting - drilling - hole treatment (plasma treatment or sodium naphthalene activation treatment) - copper deposition - plate electricity - dry film - inspection - graphic electricity - etching - corrosion inspection - solder resistance - characters - tin spraying - forming - testing - final inspection - packaging - shipment

Summarize the difficulties in high-frequency circuit board processing

1. Copper sinking: the hole wall is not easy to be coated with copper

2. Control of line gap and sand hole of drawing, etching and line width

3. Green oil process: control of green oil adhesion and green oil foaming

4. Scratches on the board surface are strictly controlled in each PCB process.