Detailed understanding of Printed Circuit Board Assembly process

Views: 0     Author: Site Editor     Publish Time: 2023-12-05      Origin: Site


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一、What is Printed Circuit Board Assembly processing

PCBA is the abbreviation of Printed Circuit Board Assembly, Chinese meaning surface mount technology or surface mounting technology. The processing refers to the process of pasting electronic pcb components and other materials on the PCB bare board, specifically, it is a pin-free or short-lead surface assembly components (SMC/SMD, Chinese called chip components). Common such as capacitance and resistance components are SMD) installed on the surface of the Printed Circuit Board (PCB) or other substrate surface, through reflow welding or dip welding and other methods to weld the circuit assembly technology. It is a popular processing technology in the electronic assembly industry.

二、What is Advantages of PCBA

Electronic products pursue miniaturization, and previously used perforated plug-in components can no longer be reduced. The function of electronic products is more complete, and the integrated circuit (IC) used has no perforated components, especially large-scale, highly integrated ics, and surface patch components have to be used. Product mass, production automation, manufacturers to low cost and high output, produce high-quality products to meet customer needs and strengthen market competitiveness.

The advantages of pcb board assembly: high assembly density, small size and light weight of electronic products, the volume and weight of the pcb components are only about 1/10 of the traditional plug-in components, generally after the use of PCBA, the volume of electronic products is reduced by 40% to 60%, and the weight is reduced by 60% to 80%. High reliability, strong vibration resistance, low solder joint defect rate, good frequency characteristics, reduce electromagnetic and radio frequency interference, easy to achieve automation, improve production efficiency, reduce costs up to 30%~50%, save materials, energy, equipment, manpower, time, etc., are the advantages of pcb board assembly.

三、Detailed process of PCBA manufacturing

1、 Material purchasing, processing and inspection

The material buyer purchases the material according to the BOM list provided by the customer to ensure that the production is basically correct. After the purchase is completed, material inspection processing, such as pin cutting, resistance pin forming, etc. Inspection is to better ensure the quality of production.

2、PCB steel mesh making

If the steel mesh used for screen printing is not provided by the customer, the PCBA processing supplier needs to make steel mesh according to the steel mesh file. At the same time, because the solder paste used must be frozen, the solder paste needs to be thawed in advance to the right temperature. Solder paste printing thickness is also related to the scraper, the solder paste printing thickness should be adjusted according to the PCB processing requirements.

3、 Screen printing

Screen printing, that is, screen printing, is the first process of PCBA manufacturing. The role is to leak solder paste or patch glue onto the PCB pad to prepare for component welding. With the solder paste press, the solder paste is permeated through stainless steel or nickel steel mesh and attached to the pad.

4、 Glue dispensing

Generally, in PCBA manufacturing, the glue used for dispensing is red glue, and the red glue is dropped on the PCB position to fix the pcb components to be welded, preventing electronic components from falling or welding due to self-weight or unfixed reasons during reflow welding. The equipment used is the dispensing machine, which is located at the front end of the PCBA production line or behind the testing equipment. Dispensing can be divided into manual dispensing or automatic dispensing, according to the needs of the process to confirm.

5、 Assembly

The role of assembly is to accurately install the surface assembly components to the fixed position of the PCB. The equipment used is the PCBA machine, which is located behind the screen printing machine in the PCBA production line. Through the functions of suction - displacement - positioning - placing, SMC/SMD components can be quickly and accurately assembled to the solder pad position specified by the PCB board without damaging the components and the printed circuit board. Assembly is generally prior to reflow soldering.

6、 Solidify

Its role is to melt the patch glue, so that the surface assembly components and the PCB board firmly bonded together. The equipment used is the curing furnace, which is located behind the PCBA machine in the PCBA production line and generally adopts heat curing.

7、 Reflow welding

Reflow soldering is the soldering of mechanical and electrical connections between the solder ends or pins of surface-assembled components and the printed board solder pad by remelting the paste solder pre-allocated to the printed board solder pad. It mainly relies on the action of hot gas flow on the solder joint, and the colloidal flux reacts physically under a certain high temperature air flow to achieve SMD welding. The equipment used is reflow furnace, which is located behind the PCBA machine in the PCBA production line.

8、 Cleaning

After the welding process is complete, the surface of the plate needs to be cleaned to remove the rosin flux and some tin balls to prevent them from causing short circuits between components. Cleaning is to place the welded PCB board in the cleaning machine to remove the solder residue on the surface of the PCB assembly board that is harmful to the human body or the flux residue after reflow welding and manual welding and the pollutants caused by the assembly process. The equipment used is the cleaning machine, the position can be fixed, can be online, or not online.

9、 Inspection

The inspection is to test the welding quality and assembly quality of the PCB assembly board after assembly. The equipment used includes magnifying glass, microscope, on-line tester (ICT), flying needle tester, automatic Optical inspection (AOI), X-RAY inspection system, function tester, etc. Position According to the need of detection, it can be configured in the appropriate place of the production line.

10、 Repair

PCBA repair is usually done to remove components that have lost function, damaged pins or misaligned components and replace them with new components. Its role is to detect the failure of the PCB board rework. The tools used are soldering iron, repair workstation, etc. Configures anywhere in the production line.

11、Visual inspection

It is the key item of manual inspection, whether the PCBA version is the changed version; Whether the customer requires the components to use substitute materials or components of the manufacturer or brand; The direction of IC, tantalum capacitor, aluminum capacitor, switch and other directional components is correct; Defects after welding: short circuit, open circuit, false parts, false welding.


Separate the products that pass the test. Generally, the packaging materials used are anti-static bubble bags, electrostatic cotton, and plastic trays. There are two main packaging methods, one is to use anti-static bubble bag or electrostatic cotton into a roll shape, separate packaging, is currently the common packaging; The second is to customize the blister disk according to the size of PCBA. Lay out the packaging on the blister tray, mainly for the more sensitive PCBA board with vulnerable patch components.

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