Special material PCB, process technology
Microwave multilayer printed circuit board; laminated plate; ceramics; Technology
The
Microwave printed circuit board refers to microwave electronic components in microwave substrate specific CCL using ordinary rigid printed board manufacturing method of production.
Current PCB high-speed signal transmission line can be divided into two categories: one is the high frequency signal transmission, its electromagnetic wave and radio related to sine wave signal transmission, such as radar, radio and television and communications (mobile phones, microwave communications, optical fiber communication etc.); the other is high logic signal transmission, this kind of products based on digital signal transmission, the electromagnetic wave and square wave transmission, this kind of product starts mainly in computer, computer application, it has been applied to home appliances and communications electronics products.
In order to achieve high-speed transmission, clear requirements on the electrical characteristics of microwave printed circuit board substrate material. To realize the low loss and low delay of transmission signal, the substrate material with small dielectric constant and dielectric loss tangent angle must be selected. The ceramic material, glass fiber cloth, polytetrafluoroethylene and other thermosetting resins are usually used.
In all of the resin, the dielectric constant of polytetrafluoroethylene (R) and dielectric loss tangent (tan delta) minimum, and high and low temperature resistance and good aging resistance, suitable for high frequency substrate materials, is currently the largest amount of microwave printed circuit board substrate material.
The base of simple introduction in the manufacturing process of filling two kinds of microwave multilayer ceramic powder of printed circuit board, discusses in detail about the laminated manufacturing technology.
2 microwave multilayer printed circuit board materials
Microwave multilayer mainly focuses on the following two kinds of high frequency dielectric material laminated printed circuit board manufacturing technology. The first is filled with ceramic powder, short glass fiber reinforced polytetrafluoroethylene (PTFE) high frequency dielectric material (RT/duroid6002 sheet); the second is filled with ceramic powder thermosetting resin copper-clad laminates (RO4350 sheet).
2.1 ceramic powder filled microwave multilayer printed circuit board manufacturing process
Process as shown in Figure 1, there are two high medium plate lamination technology.
2.2 RT/duroid6002 lamination process
2.2.1 adhesive sheet 3001
To RT/duroid6002 by high frequency dielectric sheet manufacturing microwave multilayer printed circuit board, high frequency dielectric plate suppliers for RT/duroid low dielectric constant of the adhesive sheet 3001. It is a thermoplastic fluorinated copolymer with a low dielectric constant and a low loss tangent in the microwave frequency range.
2.2.2 lamination process 1) row plate
RT/duroid6002 plate and adhesive sheet stacked alternately. In order to ensure the coincidence accuracy among layers of printed boards, four slot dowel pins are used to arrange panels. A method for placing a thermocouple probe into the non graphic region of the inner layer of the laminate to control the temperature and time of the laminate is carried out.
2) closed
When the compressor in a cold state (usually compressor temperature lower than 120 DEG C), the central board is arranged on the row, press and die for closed compressor, adjust the hydraulic system to obtain the required pressure pressure. In general, the initial pressure of 100psi is sufficient, and then the total pressure rises to 200psi to ensure the proper flow of the adhesive sheet.
3) heating
Start laminator, heated to 220 DEG C. Under normal circumstances, the maximum heating rate is controlled so that the temperature of the upper / lower plate varies from 1 DEG C to 5 DEG C.
4) insulation
Normally at 220 C for 15 min., the adhesive sheet in the molten state, and has enough time to flow and wetting sticky surface. For thicker row plate structure, the heat preservation time can be extended to 30 minutes to 45 minutes.
Cold press 5)
Closed heating system, cooling plate laminated furnace in keeping under pressure, until the furnace plate temperature to 120 DEG C. Remove the pressure and remove the template containing the laminate from the laminator.
2.2.3 problems and Countermeasures
1) bond failure
2) laminate surface spots or blistering
The reason is that the pressure is not uniform, the improper control of temperature, the inner lamination monolithic cleaning and drying is not sufficient. The solution is to use clean templates or other smooth finish materials to check flatness or pressure. A thermocouple is used to test the lamination temperature curve again. Review the cleaning and drying procedures to be pressed, and review the storage conditions and time during the preparation and bonding.
3) deformation
Because the temperature is too high or uneven pressure, should be accurate control of temperature and pressure.
2.3 RO4350 lamination process
2.3.1 semipreg RO4403
In order to achieve effective bonding material for RO4350, using RO4403 prepreg.
2.3.2 lamination process
) 1 main parameters temperature: 175 C; pressure: 40kg/cm2; time: 2 hours;
Buffer: each pad, 24 pieces of kraft paper;
Die: the low temperature (100 DEG C) into the mold, 175 DEG C start calculating lamination time; put pressure: take the segmented release pressure method.
Using the above conditions after lamination, the binding force between layers can still meet the requirements, but the poor smoothness of laminates. After many tests and referring to the lamination characteristics of the prepreg RO4403, it was decided to use the following process parameters for lamination.
2) row board
From bottom to top to bottom stainless steel mold / polyester sheet /4 RO4350 single / A
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