PCB Assembly Process and Services

smt tech

SMT PCB Assembly

Why Choose Us 7 SMT Factory lines in Shenzhen, Electronic Contract Manufacturing, 1 to 5 days production turnaround times, Productions run 100k+ units/year, R esistors and Capacitors to 01005, BGAs to .254mm, F ine Pitch to 0.4mm, ISO 9001:2015 Certified, IPC 610-A capable

Through Hole PCB Assembly

THT components have much stronger bonds with the board than SMT components do. This makes THT the best option for components that will face mechanical and environmental stress or high heat. Unlike SMT, THT assembly is not automated and relies on the skills of the operators. This makes THT assembly less reliable and more costly than SMT.

BGA PCB Assembly

One stop BGA turnkey services, We offer PCB fabrication and assembly services containing the following BGA types: Plastic BGA (PBGA) Ceramic BGA (CBGA) Micro BGA Micro Fine Line BGA (MBGA) Stack BGAs Lead BGA and leadless BGA

After all the electronic components have been soldered and mounted on a printed circuit board, the completed board is referred to as a “printed circuit board assembly” and generally abbreviated as PCBA. In a procedure known as “PCB Assembly” or “PCBA” these components are affixed to the PCBs by means of the soldering process. Components, a substrate formed of fiber glass, a copper layer that produces the traces, holes in which components may be inserted, and layers that can either be inner layers or outer layers, make up the complete PCBA. ELE is a leading PCB assembly manufacturer in China, we are able to provide turnkey PCB assembly for all industries. For example, submit quote today!

PCBA construction

The world is advancing in terms of contemporary technology at a very rapid speed, and the impacts of this can be plainly seen in our day-to-day life. Our way of life has undergone significant shifts. The evolution of technology has resulted in the production of several cutting-edge devices that simply were not imaginable even ten years ago. Electronics engineering forms the basis of various pieces of equipment, and printed circuit boards serve as their operating device.

Table of Contents

1. PCB Mounting Technologies and Their Assembly Stages

There are two primary types of mounting technologies that are utilised in today’s printed circuit board assembly industry, and both are offered by ELE Technology Co.,

1.1 Thru-Hole Technology (THT) & its Assembly Stages

Thru-Hole PCBA

The term “through hole technology” refers to a method for the construction of electronic circuits boards that involves inserting pin-through hole components onto PCB by way of holes that have been drilled into the boards. This method is used on PCB assemblies that need to be constructed and contain big components like capacitors and coils.

On most PCB boards, you’ll find components with through-hole connections. Plated through Hole (PTH) is another name for these components. The leads of these components are designed to fit through the hole on the printed circuit board. Copper traces allow these holes to interface with other holes and vias on the PCB. 

There are two primary kinds of soldering used for THT components. Following steps are performed on a thru-hole technology based PCBA.

1.1.1 Manual Soldering

Manual soldering of PCBA

The procedure of manually inserting through-hole components is quite easy to understand. In most cases, a single individual working at a single station will be assigned with the responsibility of inserting a single component into a particular PTH. After they have completed their task, the circuit board is moved to the subsequent station, where a different individual will begin the process of installing a different component. The sequence is repeated for each PTH that requires being equipped with new components. Depending on the number of PTH components that need to be placed during a single cycle of electronic board assembly production, this can be a time-consuming procedure. After all placements, the components are soldered manually. 

1.1.2 Wave Soldering

Wave soldering of PCBA

Wave soldering is an automated alternative to the traditional method of soldering by hand. Following the insertion of the PTH components into the PCB using this technique, the board is then placed on a conveyer belt and transported to a specialized oven. At this point, a hot wave of solder is splattered onto the bottom layer of the PCB, where the component leads are located. All the pins will be soldered at the same time. However, this procedure can only be used for single-sided PCBs, as the hot solder that is used to solder one side of a double-sided PCB might cause harm to the components on the opposite side of the board. Following this step, the printed circuit board manufacturing and assembly are transferred for the final inspection.

1.1.3 Final Inspection

Following the completion of the soldering stage of the PCBA process, the PCB will be subjected to a final inspection in which its functioning will be evaluated. A “functional test” is the name given to this type of examination. During the test, the PCB is put through its paces by replicating the conditions under which it will normally function. During this test, power and simulated signals are routed through the PCB, and the electrical properties of the PCB are monitored by the testers.

1.2 Surface Mount Technology (SMT) its Assembly Stages

Surface Mounted PCBA

As opposed to the typical method of PCB assembly, which involves inserting components via holes, the Surface Mount Technology subfield of electronic assembly is capable of mounting electronic components directly onto the surface of the PCB. SMT was designed to cut down on the expenses of manufacturing, as well as to make better use of the available space on PCBs. Surface mount technology made it feasible to assemble extremely complicated electronic circuits into ever-smaller assemblies while maintaining strong repeatability thanks to an increased level of automation. All of this was made possible as a direct result of the development of surface mount technology.

Following steps are performed on a surface mount technology based PCBA

1.2.1 Solder Paste Stenciling

The solder paste is first placed to the sections of the printed circuit board where the components will fit. The solder paste is applied on the stainless-steel stencil in order to accomplish this. After a mechanical fixture has been used to keep the stencil and the PCB in place, an applicator will apply solder paste uniformly to each area in the board. . The solder paste is distributed uniformly thanks to the applicator. It is necessary to utilize the appropriate quantity of solder paste in the applicator. After the applicator is withdrawn from the PCB, the paste will still be in the locations where it was intended to be. The solder paste is lead free, includes 3% silver and 0.5% copper, and has a tin content of 96.5% by weight. The solder paste is grey in appearance. When heat is applied in stage 3, this solder paste will melt, resulting in a strong connection between the components.

1.2.2 Component Placement

The process of PCB assembly continues on to the pick and place machine once the solder paste has been applied to the PCB board. This machine is a robotic device that sets surface mount components, also known as SMDs, on a prepared PCB. SMDs are responsible for most non-connector components seen on PCBs in modern times. In the subsequent phase of the PCBA manufacturing process, these SMDs are soldered onto the top layer of the board.

In the past, this step of the assembly process was traditionally carried out by hand using a pair of tweezers. The assemblers were required to choose and put the components by hand. PCB makers have, to their great relief, transformed this stage into an automated procedure in recent years. This transition took place in large part because of the tendency of robots to be more precise and more consistent than people. Even while humans can work swiftly, after a few hours of working with such small components, workers typically experience fatigue and eyestrain. Machines can operate nonstop without experiencing the same level of exhaustion.

1.2.3 Reflow Soldering

Reflow soldering is the third stage, which comes after the components have been positioned and solder paste has been applied. Conveyor belts are used in the process of reflow soldering, during which printed circuit boards and the components they contain are loaded onto the conveyor belts.

Heating reflowing process in PCBA

After this, the PCBs and components are moved by this conveyer belt inside of a large oven that has a temperature of 250 degrees Celsius. Solder will melt at this temperature. The molten solder will build joins and secure the components to the PCB. The PCB is placed in coolers after it has been subjected to high temperatures during the treatment process. The solder junctions are then solidified in a regulated manner by these coolers. By doing this, a permanent connection will be made between the SMT component and the PCB conductive layer.

1.2.4 Final Inspections

After the reflow soldering process has been completed, there is a possibility that the components might get misaligned as a consequence of some erroneous movement in the PCB holding tray. This may have led to a short circuit or an open connection. It is necessary to identify these defects, and the procedure by which this is accomplished is known as inspection. The inspection process might be either manually or automatically carried out.

Visually inspecting a PCB that contains tiny surface-mount technology (SMT) components can cause eye strain and fatigue for the personnel doing the inspection because of the small size of the components. As a result of producing erroneous findings, this approach is not suitable for use with advanced SMT boards. On the other hand, this strategy is practical for circuit boards that contain THT components and have a lower component density.

Automated inspection procedure is workable for the enormous quantities of PCB that need to be inspected. This technique makes use of an automated equipment that has high powered and high-resolution cameras positioned at a variety of different angles to see the solder junctions from a number of different perspectives. The quality of the solder connections will cause the light to reflect from them at a variety of various angles. When processing big batches of PCBs, this automated Optical Inspection (AOI) system works at a very fast pace and requires just a very short amount of time.

SMT or THT, Which one should I choose?

The choice between SMT and THT depends on several factors, such as the size, weight, speed, reliability, and cost of the components and the PCBs. Here are some advantages and disadvantages of each technology:

SMT allows for smaller PCB size and higher component density, which can improve the circuit speed and performance. SMT also requires fewer drilled holes, which makes it more affordable and faster to produce. SMT components are placed by machines at rates of thousands per hour, which reduces human error and increases soldering quality.

However, SMT may not be suitable for larger and heavier components that need strong mechanical bonds, such as connectors or power transistors. SMT can also be more difficult to repair or modify, as the components are harder to access and remove. SMT may also require more advanced design, production, and testing skills than THT.

THT provides stronger bonds for components that will be under stress or vibration, such as switches or potentiometers. THT is also ideal for fast prototyping, as it allows for easy insertion and removal of components by hand. THT can handle higher voltages and currents than SMT, which makes it more suitable for power applications

However, THT requires drilling holes on PCBs, which is expensive and time-consuming. Drilling holes also limits the routing area on multi-layer boards and reduces the circuit density. THT also requires soldering on both sides of the PCB, which makes the process more lengthy and prone to errors. THT overall is more costly than SMT.


Choosing a method of PCB assembly does take time. If your goal is low cost and fast turn PCB assembly, you’d better choose our SMT PCB Assembly service. If you want a more stable way of PCB assembly, THT assembly will be more suitable for you. The best choice depends on your specific needs and preferences. You may also consider using a combination of both technologies to achieve the best results, ELE PCB provides the best turnkey PCB assembly service among most PCB assemblers.

PCB assembly USA VS PCB assembly China

According to the U S Bare Printed Circuit Board Industry Assessment 2017.

U.S. bare PCB manufacturers possess the comparative
advantage in:

  • Lead Time
  • Quality
  • Performance

The Non-U.S. Competitors Primary Competitive Attribute was price. And China has the advantages in the following fields:

  • Labor Costs
  • Material Costs
  • Equipment Costs
  • Environmental Compliance Costs
  • Building Space Costs
  • R&D Costs


PCB Assembly Projects Offered by ELE

We are expert in PCB & PCBA manufacturing, and we offer a wide range of PCBA services including the manufacturing of following types of PCBs & PCBAs,

  • FR-4 PCB
  • Multi-layer PCB
  • Flex PCB
  • Rigid-Flex PCB
  • Metal Base PCB
  • Impedance Control PCB
  • High Density Interconnect PCB
  • High Density Multilayer PCB
  • High-TG PCB
  • Heavy Copper PCB
  • Special PCB-Advanced High Frequency PCB

Our team of highly trained engineers performs a DFM check on every Gerber file that is provided. In accordance with IPC-A6012 Class 2 or other standards, each PCB is put through the quality assurance process. Choose ELE Technology today, and you will save a lot of time on your project and work. 

Click for a comprehensive rundown of the PCB fabrication and click here PCB Assembly capabilities offered by ELE Technology Co., we cherish you as a client and look forward to serving you for the many next years to come.



ELE PCB has got the IS09001:2015, IS013485:2016, ROHS and FCC certifications. We can offer all kinds of services, including PCB manufacturing and PCB assembly, sample orders and batch orders. For PCB assembly, utilizing 7 high-speed SMT PCBA lines from Yamaha and Sony, to meet our customers’ needs. Our extended services include PCB design &PCB Layout, hardware design engineering, firmware &software development, and personalization. ELE company is honored as an excellent supplier from any company all around the world. We deeply believe that our good service and experience will completely meet your needs. Integrality, value and innovation are the forces that drive our success.



We provide technical expertise form prototype through production increasing speed to market by 20%.

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