An Innovative Multilayer PCB Manufacturer

PCB Assembly Process and Services

SMT PCB Assembly

SMT PCB Assembly

Why Choose Us?
1. 7 SMT Factory lines
2. Electronic Contract Manufacturing
3. 1 to 5 days production turnaround times
4. Productions run 100k+ units/year
5. Resistors and Capacitors to 01005
6. BGAs to .254mm, Fine Pitch to 0.4mm
7. ISO 9001:2015 Certified, IPC 610-A

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.
BGA PCB Assembly

BGA PCB Assembly

We offer PCB fabrication and BGA assembly services:
1. Plastic BGA (PBGA)
2. Ceramic BGA (CBGA)
3. Micro BGA
4. Micro Fine Line BGA (MBGA)
5. Stack BGAs
6. Lead BGA and leadless BGA

Need a PCB Assembly Quote?

ELEPCB is your trusted source for PCB assembly services. With a focus on quality and adherence to strict manufacturing standards, we deliver reliable and high-performing printed circuit boards. Our advanced technology and skilled team ensure precise manufacturing tailored to your specific requirements. Experience excellence in PCB assembly with ELEPCB as your reliable manufacturing partner.

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 fiberglass, 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.

In this post, you will learn about basic knowledge of PCB Assembly, the PCB Assembly process, different technologies SMT and THT, the PCBA in US vs PCBA in China, and the recommended manufacturer that offers excellent PCBA services, ELEPCB.

Some Basic Knowledge of PCB Assembly

To better grasp the PCB assembly process, you must first understand the PCB’s most basic unit: the base. The bottom of the PCB is made up of several layers, like these:

  • Substrate: Common substrates used as an insulating layer between two conductive copper layers are fluorine series resins, polyphenylene (PPO) or polyphenylene oxide (PPE) resins and modified epoxy resins, fluorine series dielectric substrates, polytetrafluoroethylene (PTFE) and so on.
  • Copper: A thin layer of copper foil is added to improve the thermal resistance and current carrying capacity of the PCB.
  • Solder Resist: Usually a green solder resist is used to insulate copper wires from other conductive materials.
  • Screen Printing: The final layer of the PCB is silk-screened, which helps provide text indicators for components. The screen printing layer helps to identify test points, part numbers, warning symbols, logos and manufacturer’s marks.

For all types of PCBs, the basic layers described above are almost always the same. The only difference between rigid, flexible, metalcore, surface mount, or through-hole PCBs is the substrate used. The manufacturer chooses the substrate after considering the application. 

Composition of PCB Assembly
Composition of PCB Assembly

PCB Assembly Process

Stenciling: First, solder paste (tiny particles of solder paste mixed with flux) is put on the board. Most PCB manufacturers employ stencils (which come in a variety of sizes, shapes, and sizes to fulfill the specification) to apply the precise amount of solder paste to specified portions of the board.

Placement of Components: This part of the PCB assembly process is now completely automated. Picking and positioning parts (e.g., surface mount assemblies) was previously done manually but is now done by robotic pick-and-place machines.

Soldering Processes (Wave Soldering or Reflow Soldering): After applying the solder paste and installing all surface mount components, the next step is to cure the solder paste into the proper position. This is the reflow soldering step in the PCB assembly process. To melt the solder in the paste, the assembly and its components are run on a conveyor belt through an industrial-grade reflow oven. Once the melting is finished, the assembly will pass through the conveyor belt and be exposed to a series of coolers. The melted solder will ultimately cool and cure.

SMD Assembly - Reflow Soldering
SMD Assembly - Reflow Soldering
THT Assembly - Wave Soldering
THT Assembly - Wave Soldering

PCB Inspection and Testing: This stage assists in detecting poor-quality connections, misplaced components, and short circuits, as well as any potential concealed faults. It is divided into three stages: manual inspection, automatic optical inspection, and X-ray inspection to ensure the board’s performance. If errors are found, the boards are sent back for rework.

Cleaning: Because the soldering procedure leaves quite a bit of flux on the PCB, the components must be cleaned before the final board is handed to the customer. After cleaning, the board is allowed to dry completely using compressed air. Finally, the consumer can inspect it.

PCB Mounting Technologies and Their Assembly Stages

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

Through Hole Technology (THT) and Assembly Stages

Through Hole Technology (THT)
Through Hole Technology (THT)

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.

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.

Manual Soldering

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 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. 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.

THT - Manual Soldering
THT - Manual Soldering - LED

Wave Soldering

THT - Wave soldering of PCBA Process

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.

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.

Surface Mount Technology (SMT) and Assembly Stages

Surface Mount Technology (SMT)
Surface Mount Technology (SMT)

As opposed to the typical method of PCB assembly, which involves inserting components via holes, the SMT 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.

The following steps are performed on a surface mount technology based PCBA:

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.

Component Placement

The process of PCB assembly continues 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.

SMT Component Placing

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
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.

Final Inspections

Automated inspection procedure is workable for the enormous quantities of PCB that need to be inspected. This technique makes use of 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 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.

Mixed PCB Assembly

Mixed PCB Assembly
Mixed PCB Assembly

Type 1: Single-Sided Mixing

  1. Solder paste printing
  2. SMD parts placement
  3. Reflow soldering
  4. THT component placement
  5. Wave soldering

Type 2: One Side SMT and One Side THT

  1. Surface mount adhesive
  2. SMD component placement
  3. Solidification
  4. Flip
  5. THT component placement
  6. Wave soldering

Type 3: Double-sided Mixing

  1. Solder Paste Printing
  2. SMD parts placement
  3. Reflow soldering
  4. Flip
  5. SMT adhesive
  6. SMD parts placement
  7. Solidification
  8. Flip
  9. THT component placement
  10. Wave Soldering

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:


  • Advantages: 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.
  • Disadvantages: 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.


  • Advantages: 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.
  • Disadvantages: 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.

ELE is a leading PCB assembly manufacturer. We can provide turnkey PCB assembly service among most PCB assemblers and help you choose the most suitable PCBA service. Ready to transform your product line? Submit a quote today, and schedule a consultation with our PCB Experts!

China PCB Assembly vs US PCB Assembly

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

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

  • Lead Time
  • Quality
  • Performance

ELEPCB: Top-Rated PCB Assembly Service

PCB and PCB Assembly

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PCB Assembly Production Samples

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.