Multilayer PCB Fabrication

Product Detail

Type: High TG, High CTI, High Frequency, Heavy Copper

Material:FR4, CEM-1, CEM-3, Aluminum ,Copper, Iron, Rogers, Taconic, Teflon

Layer Count:1 Layer to 26 layers

Test:Gold Connector, Peelable Mask, Impendence Control, Blind & Buried hole

Finished:Leaded / Lead Free HASL, ENIG,OSP, Immersion Tin/Silver

PTH:Min 0.2mm

NPTH:Min 0.25mm

Max finished size:580mm x 700mm

Min Line Width/Space:3mil/3mil

Multilayer boards use more single-sided or double-sided wiring boards. A printed circuit board with one double-sided as the inner layer and two single-sided as the outer layer, or two double-sided as the inner layer and two single-sided as the outer layer, alternately connected by a positioning system and an insulating adhesive material Together, the conductive patterns are connected to each other according to the design requirements to become four-layer and six-layer printed circuit boards, also known as multi-layer printed circuit boards.

Multilayer PCB board production process

1. Material selection

With the development of high-performance and multi-functional electronic components, as well as high-frequency and high-speed signal transmission, electronic circuit materials are required to have low dielectric constant and dielectric loss, as well as low CTE and low water absorption. rate and better high-performance CCL materials to meet the processing and reliability requirements of high-rise boards.

2. Laminated structure design

The main factors considered in the design of the laminated structure are the heat resistance, withstand voltage, amount of glue filling and thickness of the dielectric layer, etc. The following principles should be followed:

(1) The prepreg and core board manufacturers must be consistent.

(2) When the customer requires high TG sheet, the core board and the prepreg must use the corresponding high TG material.

(3) The inner layer substrate is 3OZ or above, and the prepreg with high resin content is selected.

(4) If the customer has no special requirements, the thickness tolerance of the interlayer dielectric layer is generally controlled by +/-10%. For the impedance plate, the dielectric thickness tolerance is controlled by the IPC-4101 C/M class tolerance.

3. Interlayer alignment control

The accuracy of the size compensation of the inner layer core board and the control of the production size need to be accurately compensated for the graphic size of each layer of the high-rise board through the data collected in production and the experience of historical data for a certain period of time, so as to ensure the expansion and contraction of the core board of each layer. consistency.

4. Inner layer circuit technology

For the production of high-rise boards, a laser direct imaging machine (LDI) can be introduced to improve the graphics analysis ability. In order to improve the line etching ability, it is necessary to give appropriate compensation to the width of the line and the pad in the engineering design, and confirm whether the design compensation of the inner layer line width, line spacing, isolation ring size, independent line, and hole-to-line distance is reasonable, otherwise change engineering design.

5. Pressing process

At present, the interlayer positioning methods before lamination mainly include: four-slot positioning (Pin LAM), hot melt, rivet, hot melt and rivet combination. Different product structures adopt different positioning methods.

6. Drilling process

Due to the superposition of each layer, the plate and copper layer are super thick, which will seriously wear the drill bit and easily break the drill blade. The number of holes, drop speed and rotation speed should be adjusted appropriately.

The difference between multi-layer circuit board and double-sided board:

1. A multi-layer pcb circuit board is a printed circuit board that is laminated and bonded by alternating conductive pattern layers and insulating materials. The number of conductive pattern layers is more than three, and the electrical interconnection between layers is realized through metallized holes.

2. Comparing the production processes of both parties, the multilayer board adds several process steps such as inner layer imaging, blackening, lamination, etchback and decontamination.

3. Multi-layer boards are more stringent than double-sided boards in terms of certain process parameters, equipment accuracy and complexity. For example, the quality requirements for the hole wall of the multi-layer board are stricter than that of the double-layer board, so the requirements for drilling are higher.

4. The number of stacks per drilling, the rotational speed and feed of the drill bit are different from those of the double-sided board.

5. The inspection of finished and semi-finished products of multi-layer boards is also much stricter and more complicated than that of double-sided boards.

6. Due to the complex structure of the multi-layer board, the glycerin hot-melt process with uniform temperature is adopted; the infrared hot-melt process that may cause local temperature rise is not used.

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