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Undoubted knowledge of circuit board basics
Time: 2018/5/7   Hits: 21292 
Introduce the following five aspects:
1. Introduction to the circuit board
2. Circuit board material introduction
3. Basic layout of the circuit board
4. Circuit board production process
5. Circuit board case sharing
 
1. Introduction to the circuit board
Flexible printed circuit board
Flexible printed circuit board (FlexPrint Circuit, referred to as "FPC"), is flexible
A single-layer, double-layer or multi-layer printed circuit board made of a substrate. It is light, thin, short, small, high
Density, high stability, and flexible structure, in addition to static bending, can also be used for dynamic bending, curling and folding.
 
 
 
2. Rigid printed circuit board
Printed Circuie Board ("PCB") is not easily deformed
The printed circuit board made of rigid substrate material is in a flat state during use. It has high strength
It is not easy to warp, and the patch components are installed firmly.
 
3. Soft and hard board
RigidFlex (RigidFlex) is a combination of rigid and flexible substrates that are selectively laminated together.
A special flexible printed circuit board that is closely structured and forms an electrical connection with metallized holes. It has a high
Density, thin wire, small aperture, small size, light weight, high reliability, vibration, impact,
Its performance is still stable in wet conditions. Flexible, three-dimensional installation, effective use of installation space, wide
It is widely used in portable digital products such as mobile phones, digital cameras, and digital video cameras. Gang-flexible board
It will be used more in the field of packaging, especially in the consumer sector.
 
2. Introduction of circuit board materials
 
1, conductive medium: copper (CU)
- Copper foil: rolled copper (RA), electrolytic copper (ED), high ductility electrolytic copper (HTE)
- Thickness: 1/4OZ, 1/3OZ, 1/2OZ, 1OZ, 2OZ, which is the more common thickness
-OZ (ounces): copper foil thickness unit; 1OZ = 1.4 mil
2. Insulation: Polyimide, Polyester, Polyethylene (PEN)
- The more common one is polyimide (referred to as "PI")
-PI thickness: 1/2 mil, 1 mil, 2 mil, which is the more common thickness
-1 mil = 0.0254mm = 25.4um = 1/1000 inch
3. Adhesive: epoxy resin, acrylic.
- The epoxy resin is more commonly used, and the thickness is different depending on the manufacturer.
4, CCL (Cucladlaminates, referred to as "CCL"):
 
- Single-sided copper clad laminate: 3LCCL (with glue), 2LCCL (without glue), the following is an illustration.
 
- Double-sided copper clad laminate: 3LCCL (with glue), 2LCCL (without glue), the following is an illustration.
 
5, coverlay (Coverlay, referred to as "CVL"): consists of an insulating layer and an adhesive, covering the wire,
Protects and insulates. The specific laminate structure is as follows
 
 
2. Conductive silver foil: electromagnetic wave protective film
- Type: SF-PC6000 (black, 16um)
-Advantage: Ultra-thin, good sliding performance and flexural performance, suitable for high temperature reflow
Welding, good dimensional stability.
The commonly used one is SF-PC6000, and the laminated structure is as follows:
Three. Rigid-Flex stack display
 
4. Circuit board production process
 
 
1. Cutting material: cutting/Shearing
 
2, mechanical drilling CNCDrilling
 
3, plated through hole PlatingThroughHole
 
 
 
 
 
4, DES process (five songs)
(1). Film (dry film)
 
(2). Exposure
Working environment: Huang Guang
Purpose of the work: optical polymerization of the transparent area and dry film of the film by UV light irradiation and Philippine
Reaction, the film is a brown place, UV light can not penetrate, the film can not be right
The dry film of the film should be optically polymerized.
 
(3). Development
Working solution: Na2CO3 (K2CO3) weak alkaline solution
Purpose of the work: Partially clean the dry film without polymerization by using a weak alkaline solution
 
(4). Etching
Working solution: acid oxygen water: HCl + H2O2
Purpose of the work: The copper exposed after development is etched away by using a chemical solution to form a pattern transfer.
 
(5). Stripping film
Working solution: NaOH strong alkaline solution
 
5, AOI
Main equipment: AOI, VRS system
The copper foil that has formed the line is missing through the AOI system scan detection line. The standard line image information is stored in the AOI host in the form of data. The CCD optical image capture head scans the line information on the copper foil into the host and compares it with the stored standard data. When there is an abnormality, the abnormal point position is transmitted to the VRS host by the number record. . . . On the VRS, the copper foil is magnified 300 times, and sequentially displayed according to the disadvantages recorded in advance, and it is judged by the operator whether it is a true defect, and the water-resistant pen is marked in the defect position for the true defect. In order to facilitate follow-up workers to classify the defects and repair and repair. The operator judged with a 150x magnifying glass
Types of defects, classification statistics form quality reports, and feedback to the previous process to facilitate the timely implementation of improved measures. Because the single panel has fewer disadvantages and lower cost, it is difficult to use AOI to interpret, so it is directly inspected by artificial naked eye.
 
 
 
6, fake stickers
Protective film function: 1) Insulation and solder resistance;
2) Protection circuit;
3) Increase the flexibility of the soft board and the like.
 
7, hot pressing
Working conditions: high temperature and high pressure
 
 
8, surface treatment
After the hot pressing, the exposed position of the copper foil needs to be surface treated.
Ways are based on customer requirements
 
9, silk screen
The main equipment: screen printing machine. Oven. UV dryer. Screen plate making equipment through the screen printing principle to transfer ink to the product. Main printing product batch number, production cycle, text, black shadow, simple line and other content. By positioning PIN will Product and screen positioning, the ink is squeezed onto the product by the blade pressure. The screen is part of the text and pattern.
Separately, no text or pattern part is sealed by the emulsion to prevent the ink from leaking. After printing, it is dried in the oven, and the printed layer of text or pattern is closely integrated on the surface of the product. Some special products require some special lines, such as single Adding a few lines to the panel to achieve the dual panel function, or adding a layer of masking to the double panel must be achieved by printing. If the ink is a UV drying ink, it must be dried using a UV dryer. Common problems: missing, contaminated, gapped , protrusions, shedding, etc.
 
10, testing (O / S detection)
Test fixture + test software for full inspection of the circuit board
 
11, punching
Corresponding shape film: knife film, laser cutting, etching film, simple steel mold, steel mold
 
12, processing combination
The processing combination is to assemble the ingredients according to the customer's requirements.
A. Stainless steel reinforcement
B. 铍 copper sheet / phosphor copper sheet / nickel plated steel sheet reinforcement
C.FR4 reinforcement
D.PI reinforcement
13, inspection
Inspection items: appearance, size, reliability
Testing tools: secondary element, micrometer, caliper, magnifying glass, tin furnace, tension
 
14, packaging
How to work: 1. Plastic bag + cardboard
2. Low adhesion packaging
3. Vacuum box
4. Special vacuum box (antistatic rating)
 
Double-sided PCB board production flow chart
 
Soft and hard combination board production flow chart
 
Five. Circuit board case sharing
 
First, the design plan
1. Description of the program:
• The new COF solution is a reinforced and chip-attached area on a one-piece steel sheet, see the FPC schematic.
• Main uses:
• 1. Let the sensor minimize the surface of the uneven circuit board, directly with the sensor and the flat steel sheet
The surface is attached so that the sensor is perpendicular to the optical axis of the optical lens, reducing the opacity.
• 2. On the scheme of ≤0.3mm, the new COF flatness is better than the soft and hard combination board, under the premise of ensuring the flatness
, to achieve the purpose of reducing the height of the module.
• 3.sensor is in direct contact with the steel sheet to enhance thermal conductivity.
 
2. Design plan
1).P8V12G-621-00 circuit board (the structure is as follows:)
The thickness of the circuit board design is 0.3mm, and the height of the steel sheet boss is 0.02mm.
 
2). P8V12G-621-00 circuit board (wiring diagram is as follows:)
 
3). P8V12G-621-00 circuit board (stacked as follows:)
 
 
4). Limitation evaluation of circuit board design:
1. The purple small frame in the figure is the steel sheet support area;
2. The support area is distributed diagonally with SENSOR;
3. The minimum window opening area of the support area is 0.5*0.5, the larger the area is
The better the flatness;
4, the module head size ≥ 8.5 * 8.5;
5, the number of SENSOR pins ≤ 80;
6, MIPI2Lane output is more favorable than 4Lane output
line;
7. MIPI is more advantageous when it is located at the proximal end of the connector (as shown on the right)
MIPI trace below the pad);
 
3. Comparative analysis of advantages and disadvantages
 
4. Flatness data comparison:
Flatness comparison of different types of P8V12G:
 
Comparison of the flatness before and after the furnace under different types of P8V12G:
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