Electronic product production technology

The first one:1.1the role of PCB.

The function of PCB is to provide the foundation for connecting the first-class components with other necessary electronic circuit components, and form modules or finished products with specific functions. Therefore, PCB plays the role of integrating and connecting all functions in the whole electronic product, so when the function of electronic product fails, PCB is often the first to be questioned. Figure 1. 1 is a schematic diagram of the electronic packaging hierarchy.

Development of 1.2 PCB

1. As early as 1903, Mr. Albert Hansen first applied the concept of "circuit" to the telephone switching system. Cut the circuit conductor with metal foil, stick it on wax paper, and stick a layer of wax paper on it, which becomes the prototype of PCB mechanism. See figure 1.2.

2. By 1936, Dr. Paul Eisner had really invented PCB manufacturing technology and published many patents. Today's printing etching (photo image transfer) technology is inherited from its invention.

1.3 PCB types and manufacturing methods

Materials, layers and processes are diversified to meet different electronic products and their special needs. The following summarizes some general differences to briefly introduce the classification of PCB and its manufacturing methods.

1.3. 1 PCB type

A. by material

A. Organic materials

Phenolic resin, glass fiber/epoxy resin, polyurethane, BT/ epoxy and so on all belong to it.

B. inorganic materials

Aluminum, copper-invar copper, ceramics, etc. All belong to it. Mainly take its heat dissipation function.

B. distinguish by the hardness of the finished product.

A. Rigid PCB

B the flexible PCB of the flexible board is shown in figure 1.3.

C rigid-flexible PCB of soft and hard board is shown in figure 1.4.

C. by structure

A. the veneer is shown in figure 1.5.

B. See figure 1.6 for double panels.

C multilayer board is shown in figure 1.7.

D. According to the purpose: communication/consumer electronics/military/computer/semiconductor/electric measuring board, as shown in figure1.8bga.

Another kind of injection-molded stereo PCB is rarely used, so I won't introduce it here.

1.3.2 Introduction of manufacturing method

A. subtraction, the process of which is shown in figure 1.9.

B additive process can be divided into semi-additive process and total additive process, as shown in figure1.101.1.

C. In order to cope with the change of IC package, other advanced technologies have been expanded. This CD only mentions them but does not introduce them, because many of them are still confidential, difficult to obtain or not mature enough. This CD-ROM takes the traditional negative multi-layer board manufacturing process as the main axis, introduces each manufacturing process in a simple way, and discusses the future trend of PCB with advanced technical concepts.

2.3. 1 Data that the customer must provide:

When an electronics factory or an assembly factory entrusts a PCB workshop to produce bare boards, it must provide the following data for production. See table material data sheet for pre-production design.

The data in the above table is a necessary item, and sometimes the customer will provide a sample, a part drawing, a guarantee (to ensure that the raw materials and consumables used in the process do not contain some toxic substances) and so on. Manufacturers should judge the importance of these extra data by themselves to avoid missing business opportunities.

2.3.2. Information comments

Faced with so much data, the next working procedures and key points of the design engineer before the system are as follows.

A. Review the customer's product specifications, and see the receiving process capability checklist for the review items.

B. Bill of materials

According to the above data, through examination and analysis, the brand, model and specification of raw materials are determined through the expansion of BOM. The main raw materials include: substrate (laminate), film (preg), copper foil (solder mask), text ink (legend) and so on. In addition, the customer's requirements for smoothness will affect the choice of technology, and of course there will be different material requirements and specifications, such as soft and hard gold, plastic spraying, OSP and so on.

Table summarizes the factors that may affect the selection of raw materials in customer specifications.

C. The above is the review of new data, and samples will be made after the review. If it is old data, it is necessary to check whether there is an ECO (Engineering Change Order) before the audit.

D. typesetting

The choice of typesetting size will affect the profitability of this material. Because the substrate is the main raw material cost (typesetting optimization can reduce the waste of plates); Correct typesetting can improve productivity and reduce defective rate.

Some factories think that a certain working size can meet the maximum productivity, but the cost of raw materials increases a lot. Here are some directions to consider:

In general production cost, direct and indirect raw materials account for about 30~60% of the total cost, including substrate, film, copper foil, solder mask, dry film, drill bit, heavy metals (copper, samarium, lead), chemical consumables, etc. The consumption of these raw materials is directly related to whether the typesetting size is appropriate. When most electronic factories make circuit layout, they will do continuous design to make the assembly have the highest productivity. Therefore, the designer of PCB factory should communicate closely with customers before production, so that the size of contiguous typesetting can have the best utilization rate when typesetting into working panel. To calculate the most suitable typesetting, the following factors must be considered.

A the minimum number of tools and the maximum utilization rate of the substrate (cutting method and edging treatment should be considered).

B the dimensions of copper foil, film and dry film should match the dimensions of the working panel to avoid waste.

C. Minimum dimension between workpieces and minimum dimension of plate edges used as tools or calibration systems.

The maximum size limit or effective working area size possible for each process.

E different product structures have different production processes and different typesetting restrictions. For example, the typesetting spacing of the golden finger board is larger, and the direction should be considered, and the test fixture or test sequence is different. Larger working size can meet greater productivity, but the cost of raw materials has increased a lot, and the manufacturing capacity of equipment needs to be improved. How to reach a balance point, design standards and engineers' experience are very important.

2.3.3 Start the design.

After all the data are checked correctly, start the division of labor design:

A. After the flow chart is confirmed by data review and analysis, the design engineer will decide the most suitable process steps. The production process of traditional multilayer board can be divided into two parts: inner layer production and outer layer production. The following icons are for reference. See Figure 2.3 and Figure 2.4.

B.CAD/CAM operation

A. Input Gerber data into the used CAM system, and define the aperture and shape at this time. At present, many PCB CAM systems can accept IPC-350 format. Some CAM systems can generate external NC routing files, but general PCB layout design software does not. Some professional software can set the parameter output program directly, independently or with NC router.

The shapes are round, square and rectangular, and there are also more complicated shapes, such as the inner layer of the hot pad. At the beginning of design, the relationship between aperture code and shape should be made clear first, otherwise a series of subsequent designs will not be carried out.

B. Checklist at design time

After checking according to the checklist, we can know the possible output and cost estimate of manufacturing materials.

C. Precautions for typesetting of working panel:

-PCB typesetting engineers will make some auxiliary marks as reference to help remind or pay attention to some matters during design, so they must be removed before entering typesetting. The following table lists several projects and their impacts.

-The choice of typesetting size will affect the profitability of this material. Because the substrate is the main raw material cost (typesetting optimization can reduce the waste of plates); Correct typesetting can improve productivity and reduce defective rate.

Some factories think that a certain working size can meet the maximum productivity, but the cost of raw materials increases a lot. Here are some directions to consider:

In general production cost, direct and indirect raw materials account for about 30~60% of the total cost, including substrate, film, copper foil, solder mask, dry film, drill bit, heavy metals (copper, samarium, lead, gold), chemical consumables, etc. The consumption of these raw materials is directly related to whether the typesetting size is appropriate. When most electronic factories make circuit layout, they will do continuous design to make the assembly have the highest productivity. Therefore, the designer of PCB factory should communicate closely with customers before production, so that the size of contiguous typesetting can have the best utilization rate when typesetting into working panel. To calculate the most suitable typesetting, the following factors must be considered.

1. The number of cutters is the least, and the utilization rate of base material is the highest (cutting mode and edging treatment should be considered).

2. The size of copper foil, film and dry film should match the size of the working panel to avoid waste.

3. Minimum dimension between workpieces, and minimum dimension of plate edge used as tool or calibration system.

4. Possible maximum size limit or effective working area size of each process.

5 Different product structures have different production processes and different typesetting restrictions. For example, the typesetting spacing of the golden finger board needs to be large and directional, and its test fixture or test sequence is also different.

Larger working size can meet greater productivity, but the cost of raw materials has increased a lot, and the manufacturing capacity of equipment needs to be improved. How to reach a balance point, design standards and engineers' experience are very important.

-In the typesetting process of the working panel, the following matters should be considered to make the process smooth, and the matters needing attention in typesetting should be listed.

D. negatives and procedures:

-After editing and typesetting in CAM system, the negative will be drawn by laser plotter with the help of D code file. The negatives to be drawn include internal and external wiring, external solder mask and text negatives.

With the increasing linear density and stricter tolerance requirements, the size control of negative film is a major issue for many PCB factories at present. Table is a comparison table between traditional film and glass film. The proportion of glass negatives has been increasing. Film manufacturers are also actively studying alternative materials to make dimensional stability better. Such as a dry bismuth metal film.

Generally speaking, the preservation and use of traditional negatives should pay attention to the following matters:

1. Control of ambient temperature and relative temperature

2. Pre-adaptation time for taking out new negatives.

3. Methods of acquisition, dissemination and preservation

4. Cleanliness of the placement or operation area

-Procedures

Including primary and secondary drilling programs and shape routing programs, in which NC routing programs usually need to be handled separately.

E. design for manufacturing. PCB layout engineers don't know much about PCB manufacturing technology and matters needing attention in each process, so only electrical, logic, size and so on are considered when laying out lines. , and seldom consider others. Therefore, before PCB manufacturing, design engineers must correct some circuit characteristics from the perspective of productivity and output. For example, the circular connection pad is modified into a teardrop shape, as shown in Figure 2.5, in order to maintain the minimum width of the pad ring when a hole is misaligned during the manufacturing process.

However, the modifications made by engineers before manufacturing sometimes affect the characteristics and even performance of customers' products, so we have to be cautious. The PCB factory must have a set of specifications edited according to the process characteristics in the factory, which can not only improve the product yield and productivity, but also serve as a communication language with PCB line layout personnel, as shown in Figure 2.6.

C. Tool operation

Refer to AOI and electric measuring net list file .. AOI generates data acceptable to AOI system from CAD reference file with tolerance, and electric measuring net list file is used to make electric measuring fixture.

second

Introduction of circuit board process flow

A, double panel process:

Copper clad laminate (CCL) cutting → drilling) → copper plating (PTH)→ copper plating on the whole board → pattern ink or dry film → panel electroplating) → etching → semi-inspection IQC→ screen printing solder resist ink and character ink (SS) or pasting solder resist dry film →

2. Process flow of multilayer board:

Cutting copper foil) → inner layer pattern) → inner layer etching) → black oxidation) → inner layer → lamination or pressing process → drilling) → copper deposition (PTH)→ panel electroplating. ) → external etching) → semi-inspection IQC→ screen printing solder resist ink and character ink (SS) or sticking solder resist dry film → hot air leveling or tin spraying (HAL)→ flapping) → FQC)→ electrical measurement E measurement → packaging.