Printed Circuit Board Assembly Basics


3D Printed Circuit Board Assembly

Printed Circuit Board Assembly is a complex process involving many different phases, and also the key process for realizing the functions of the final product. The in-house PCB assembly services provided by uetpcbmake ordering your turnkey PCB manufacturing and assembly a hassle-free experience because you can rely on the professional support team and 8 state-of-art assembly lines to help you navigate every step of the process. In this post, we define some of the basic knowledges of Printed Circuit Board Assembly process, involving solder paste printing, SPI, Pick-and-Place, AOI, Reflow Soldering, PTH Assembly and X-ray. For detailed information, you can visit its specific page. As a PCB fabrication and assembly manufacturer, it’s necessary to let you know what our PCB assembly services are.

PCB Assembly Process:

Solder Paste Printing

Solder paste is a grey combination material used in the fabrication of printed circuit board assembly to connect surface mount components to pads on the PCB. It also possible to solder thru-hole pin in paste components by printing solder paste in or over the holes. The solder paste printing stage of the PCB assembly process is vitally important. Through the windows of the SMT stencil, the solder paste will be printed onto the pads of bare PCB with our Automated Solder Paste Printer from USA.


SPI is the next step of PCB assembly process that is the abbreviation of Solder Paste Inspection, which is to check the solder paste deposits quality on the pads. SPI process makes our PCB assembly services apart from those PCB manufacturing and assembly suppliers who haven’t such machine. we can 100% conduct this inspection with our KY-8030-2 made by KOH YOUNG from South Korea. SPI can improve PCB assembly quality, production yield and the performance of the PCBA in finished product. Making your Printed Circuit Board Assembly projects under our manufacturing roof, you will be more confidence in launching your products to the market.


SMT component placement systems, commonly called pick-and-place machines. When the bare PCB, covered good quality solder paste, comes to SMDs pick-and-place process, our advanced robotic machines Fuji NXT-II /NXT-III /XPF-L, and Panasonic NPM-D3 /NPM-TT2 machines will play the key role in the Printed Circuit Board Assembly to place SMDs onto a printed circuit board. Good robotic machines will lead to high placement precision and make us apart from other PCB manufacturing and assembly providers once again.


Automated Optical Inspection is a visual inspection of printed circuit board assembly with uncovered metal shields before reflow soldering, or those PCB assemblies without metal shields after reflow soldering. The CCD camera of our OMRON VT-RNS from Japan autonomously scan the device under the test for both catastrophic failure and quality defects. It is commonly used in the PCB manufacturing process because it is a non-contact test method. AOI is implemented at many stages through the manufacturing process. If the PCB assembly services from your supplier without AOI, how can they be trusted and reliable in production yield?

Reflow Soldering

Without precision placement without defects after AOI, the printed circuit board assembly with components bonding will be conveyed to the reflow oven to melt and cool the solder paste between the components and PCB, to realize actual components soldering. Our Heller 1913 MK3 and 1936 MK5 reflow ovens from USA are comprised of many heaters whose main function is to heat the board to a precision temperature and control the level of cooldown as the solder hardens. This process is crucial to the creation of properly functioning electronics.

PTH Assembly

PTH Assembly is a method of soldering electronic components in place by hand using drilled holes in the printed circuit board assembly and connecting pads. This technique creates a stronger physical bond of the component to the PCB board but is much more time consuming and the cost of the PCB can increase due to the higher volume of drilled holes.


When the finished PCB assembly passed reflow oven, and /or AOI, it will pass our x|aminer (Phoenix) X-ray inspection. With the application of high-density packaging technology, the PCB assembly services provided has also brought new challenges to non-destructive technology. In the PCBA industry, the assembly quality of components is getting more and more attention from PCB fab and assembly provider, like uetpcb. Components are soldered on the PCBA board, the soldering of the components cannot be seen from the appearance. Therefore, the X-RAY equipment is used to test the soldering, and the soldering bubbles are observed.

Except these basic knowledges of Printed Circuit Board Assembly, you can check to know more about our PCB assembly services on the related pages, Visual Inspection, First Article Inspection, In-circuit Testing and Functional Testing.

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