China Turnkey PCB Assembly Supplier

2022-11-25 16:43:35 Turnkey PCB Assembly 164 Viewed

Summary​The processing process of China turnkey PCB assembly involves many links. In order to produce good products, the quality of each link must be controlled. Generally, China turnkey PCB assembly consists of a series of processes such as PCB circuit board manufacturing, component procurement and inspection, SMT patch processing, plug-in processing, program firing, testing, and aging....

China Turnkey PCB Assembly Process

The processing process of China turnkey PCB assembly involves many links. In order to produce good products, the quality of each link must be controlled. Generally, China turnkey PCB assembly consists of a series of processes such as PCB circuit board manufacturing, component procurement and inspection, SMT patch processing, plug-in processing, program firing, testing, and aging.

1. PCB circuit board manufacturing

After receiving the China turnkey PCB assembly order, analyze the Gerber file, pay attention to the relationship between the PCB hole spacing and the board's load-carrying capacity, do not cause bending or breakage, and whether the wiring considers key factors such as high-frequency signal interference and impedance.

2. Component procurement and inspection

The procurement of components requires strict channel control, purchasing from big merchants and original factories, and 100% eliminating second-hand and counterfeit materials. In addition, set up a special incoming material inspection post to strictly check the following items to ensure that there are no defects in the parts.

PCB: reflow oven temperature test, no flying wires, whether the hole is blocked or ink leakage, whether the board surface is bent, etc.;

IC: Check whether the screen is completely consistent with the BOM, and keep constant temperature and humidity;

Other commonly used materials: check silk screen, appearance, power-on measurement, etc. The inspection items are carried out according to the random inspection method, and the proportion is generally 1-3%.

3. SMT assembly processing

Solder paste printing and reflow oven temperature control is key. The use quality and process requirements of laser steel mesh are very important. According to the requirements of the PCB, some need to increase or decrease the stencil holes, or use U-shaped holes to make the stencil according to the process requirements. The temperature and speed control of reflow soldering is critical to solder paste wetting and soldering reliability, and can be controlled according to normal SOP operating guidelines. In addition, AOI testing must be strictly implemented to minimize adverse effects caused by human factors.

4. Dip Insert Treatment

During the insertion process, the mold design of wave soldering is the key. How to use the mold to maximize the good products after the furnace is a process that PE engineers must constantly practice and sum up experience.

5. Program Combustion

In the DFM report, it can be suggested to set some test points (test points) on the PCB. The purpose is to test the continuity of the PCB and the China turnkey PCB assembly circuit after soldering all the components, which can test the various touch behaviors more intuitively. Functionality changes throughout the China turnkey PCB assembly to test functional integrity.

6. China Turnkey PCB assembly board test

For orders with turnkey PCB assembly test requirements, the main test contents include ICT (circuit test), FCT (functional test), Burn In test (aging test), temperature and humidity test, drop test, etc., and operate and summarize according to the customer's test plan report data.

Causes of China Turnkey PCB Assembly Board Warping

When the PCBA board undergoes reflow soldering and wave soldering, the China turnkey PCB assembly board will be deformed due to various factors, resulting in poor soldering of the turnkey PCB assembly, which has become a headache for production personnel. Next, we will analyze the reasons for the deformation of the China turnkey PCB assembly board.

1. China Turnkey PCB assembly board furnace temperature

Each circuit board will have a maximum TG value. When the reflow temperature is higher than the maximum TG value of the circuit board, it will cause the board to soften and cause deformation.

2. PCB board

With the popularity of lead-free technology, the temperature of the furnace is higher than that of lead, and the requirements for the plate are getting higher and higher. The lower the TG value, the easier it is for the circuit board to be deformed during the furnace, but the higher the TG value, the more expensive the price.

3. Thickness of China Turnkey PCB assembly

With the development of electronic products in the direction of small and thin, the thickness of the circuit board is also becoming thinner. The thinner the circuit board, the more likely it will be deformed due to the influence of high temperature during reflow soldering.

4. China Turnkey PCB assembly board size and panel quantity

When the circuit board is reflow soldered, it is usually placed on the chain for transmission, and the chains on both sides are used as support points. If the size of the circuit board is too large or the number of panels is too large, the circuit board is likely to sag toward the middle point and cause deformation.

5. The depth of V-Cut

V-Cut will destroy the structure of the board. V-Cut cuts grooves on the original large board. Too deep V-Cut line will cause deformation of the turnkey PCB assembly board.

6. Uneven copper laying area on the China Turnkey PCB assembly board

Generally, a large-area copper foil is designed on the circuit board for grounding, and sometimes the Vcc layer is also designed with a large-area copper foil. When these large-area copper foils cannot be evenly distributed on the same circuit board when it is on the board, it will cause the problem of uneven heat absorption and heat dissipation speed. Of course, the circuit board will also expand with heat and contract with cold. At the upper limit of the TG value, the turnkey PCB assembly board will begin to soften, causing permanent deformation.

7. The connection points of each layer on the China Turnkey PCB assembly board

Today's circuit boards are mostly multi-layer boards, which have many drilled connection points. These connection points are divided into through holes, blind holes, and buried hole points. These connection points will limit the effect of thermal expansion and contraction of the circuit board, thus leading to deformation of the board.

Cleaning Process of China Turnkey PCB Assembly

1. Fully automated online cleaning machine

A fully automatic on-line cleaning machine, the cleaning machine is aimed at the residual rosin flux, water-soluble flux, no-cleaning flux/solder paste and other organic and inorganic pollutants on the surface of SMT/THT China turnkey PCB assembly after welding. Thorough and effective cleaning. It is suitable for large-volume turnkey PCB assembly cleaning. It uses safe and automated cleaning equipment to be placed on the Denso production line, and completes the entire process of chemical cleaning (or water-based cleaning), water-based rinsing, and drying online through different chambers.

During the cleaning process, the China turnkey PCB assembly passes through the conveyor belt of the cleaning machine in different solvent cleaning chambers. The cleaning solution must be compatible with components, PCB surface, metal coating, aluminum coating, labels, writing and other materials. Special parts need to consider whether they can withstand cleaning. The cleaning process is: board entry → chemical pre-washing → chemical cleaning → chemical isolation → pre-rinsing → rinsing → spraying → wind shear drying → drying

2. Semi-automatic off-line cleaning machine

A semi-automatic off-line cleaning machine, which thoroughly and effectively cleans organic and inorganic pollutants such as rosin flux, water-soluble flux, no-clean flux/solder paste, etc. remaining on the surface of SMT/THT turnkey PCB assembly after welding cleaning. It is suitable for cleaning small batches of multi-variety turnkey PCB assemblies. It can be installed anywhere in the production line through manual handling, and completes the entire process of chemical cleaning (or water-based cleaning), water-based rinsing, and drying in one cavity offline.

During the cleaning process, the China turnkey PCB assembly usually needs to be fixed by a fixture or placed in a basket. The cleaning solution must be compatible with components, PCB surface, metal coating, aluminum coating, labels, writing and other materials. Special parts need to be considered. Do not withstand cleaning. There are certain requirements for the placement density and inclination angle of the China turnkey PCB assembly in the cleaning basket, and these two factors will directly affect the cleaning effect.

3. Manual washing machine

A manual cleaning machine (also known as a constant temperature cleaning tank), which is aimed at the residual rosin flux, water-soluble flux, rosin flux, no-cleaning flux/solder paste on the surface of SMT/THT turnkey PCB assembly after welding thorough and effective cleaning of organic and inorganic pollutants. It is suitable for small batch sample turnkey PCB assembly cleaning. Through temperature control, it adapts to the manual cleaning process of MPC microphase cleaning agent, and completes chemical cleaning in a constant temperature bath.

China Turnkey PCB Assembly Processing

1. According to the customer's Gerber file and BOM list, make the process file of SMT production, and generate the SMT coordinate file

2. Check whether the production materials are ready, and confirm the PMC plan for production

3. Carry out SMT programming, and make the first board for checking to ensure that it is correct.

4. According to the SMT process, make laser steel mesh

5. Carry out solder paste printing to ensure that the printed solder paste is uniform, good in thickness, and consistent.

6. Mount the components on the circuit board through the SMT placement machine, and perform online AOI automatic optical inspection if necessary

7. Set the perfect reflow soldering oven temperature curve, let the circuit board flow through the reflow soldering, the solder paste will transform from paste, liquid to solid, and good soldering can be achieved after cooling.

8. IPQC intermediate inspection

9. The DIP plug-in process passes the plug-in material through the circuit board and then flows through wave soldering for turnkey PCB assembly welding.

10. Post-furnace process, such as cutting feet, post-welding, board surface cleaning, etc.

11. QA conducts a comprehensive inspection to ensure the quality is OK.

Get China Turnkey PCB Assembly Supplier

​The processing process of China turnkey PCB assembly involves many links. In order to produce good products, the quality of each link must be controlled. Generally, China turnkey PCB assembly consists of a series of processes such as PCB circuit board manufacturing, component procurement and inspection, SMT patch processing, plug-in processing, program firing, testing, and aging.

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