SMT Assembly for PCB – 9 Things You Should Know

SMT assembly or Surface Mount Technology is a crucial part of PCB manufacturing. SMT brings speed and reduces the labor needed for technologies like through-hole mounting.

The risks of defects rise as the SMT parts are tiny. The engineers also have less area to work due to the high-density nature of PCBs. As a result, quality can suffer!

In this post, we will present nine crucial facts about SMT assembly. Manufacturers and engineers can refer to this post and create quality PCBs. They can also place an order for the right PCB of our company.

(Automated manufacturing welding)

1: Design Phase

The actual process of SMT starts in the design phase. If you want to keep your production hassle-free, you will have design accordingly.

There are many considerations for a good PCB SMT design. You need to consider the size, thickness, and other aspects of the PCB board. Only then can you choose the right components.

While designing, you should try to reduce as many components as possible. Unnecessary clutter can compromise the quality of the PCB. It can also increase the cost of SMT assembly and PCB production.

Other things to consider include the lead length of SMT components. You need to have an adequate exposed point to make your solder joints. The design phase should take into account all considerations of SMT assembly.

（Alt – PCB design）

2: Design for Manufacturing and Assembly

PCB manufacturers should follow DFMA or Design For Manufacture and Assembly practices. DFMA helps manufacturers create the best quality PCBs with SMT assembly. The process also reduces the cost and chances of making mistakes. You can also produce more batches in less time for agile marketing.

DFMA has several considerations when it comes to SMT. You need to have the right via positions, panel design, right component positions, and more.

Adopting DFMA principles makes way for accurate PCBs that don't need changes later on. DFMA improves PCB manufacturing efficiency to a great extent. It's best if you do the DFMA and then hand the design to the PCB manufacturer.

Else, it would help if you chose a reliable PCB manufacturer like us.

(Soldering iron tips for automated manufacturing soldering and assembly of PCB boards)

3: Ensuring the Format

PCB designers need to finalize the components and plans. Only then they can send the data and design to the manufacturer. The designer has to ensure the right size to facilitate automation.

The format of the design should match the requirements of the manufacturer. Otherwise, you may have problems during the SMT assembly.

PCB designers should also run DFM checks before sending the data to manufacturers. DFM checks help identify issues in design, like missing parts and wrong measurements. Running DFM checks at this stage reduces the risks of scrapped PCBs.

You can create a batch of working PCBs that don't need rechecking or redoing. Most designers use automated solutions to run DFM checks. It also helps them ensure the right design format.

You can use the software recommended by your manufacturer to design the SMT assembly. It will reduce the risks of unmatched formats.

（Alt – PCB manufacturing tips）

4: Choose Gerber Data

For bare PCB manufacturing, Gerber data is always available. But it can be a bit time-consuming.

The effort is worth it, as all manufacturers support Gerber files. You can convert your PCB SMT assembly design to Gerber format. Then you can send it to your PCB manufacturer.

Gerber format is the standard for PCB design and manufacturing. The file consists of an ASCII text file that integrates four elements into it-

• Parameters for configurations
• Definitions of apertures
• XY coordinate placements for flash and draw commands
• Command codes for flash and draw

Your PCB design solution will generally extract Gerber data from the design itself. The flash and draw commands represent different coordinates and locations on the PCB.

Manufacturers can directly work with Gerber data and start producing your PCBs. It saves time and helps the manufacturer complete your batch quickly.

(Production and assembly of printed circuit boards in a factory.)

5: Solder Paste Printer

The solder paste machine is the first machine in the manufacturing process. Using a stencil, it applies solder paste to the required PCB pads.

Manufacturers first put solder paste on the PCB. They use a stainless steel stencil to isolate places to apply solder paste. The components in the SMT assembly will sit in these areas.

The solder paste in the printer contains small metal balls. Flux helps the solder melt and stick with the surface of the PCB.

Most manufacturers use a machine or solder printer. The tool applies solder paste in chosen areas in the right amount. The device then applies the solder on the whole stencil. As a result, all open areas get soldered for SMT assembly.

Soldering is an essential step for accurate placing of SMT devices. The components will rest on the soldered areas and then fixed via reflow soldering.

（Alt – PCB manufacturers）

6: Detect Any Defects

In the soldering process, you will have to keep full control. As if any mistake happens, it will result in more imperfections in the rest of the process.

Manufacturers adopt strict quality control processes to ensure proper soldering. Any mistake can compromise the quality and function of the PCB. Using automation is an excellent way to cut down on imperfections.

Small PCB producers use manual ways of solder checking. They can proceed to the next stage of SMT assembly only when soldering is correct. Otherwise, the location of the SMT components can also become erroneous.

 (Factory for electronic production. )

7: Carrying Out Inspections

The inspection machine within the solder paste printer is an excellent way to carry out inspection. It may be, however, a bit time-consuming. You can opt for a dedicated inspection machine that uses 3D technology.

The inspection is essential and checks the quality of the soldering. The SMT assembly process can only move forward once the verification is over. Engineers sometimes also check the boards manually, especially in the case of prototypes. If there are issues in soldering, you should address them immediately.

After checking, the PCBs head over to the next stage for component placement.

(Factory for electronic production.)

8: Take Care of Component Placement

Component placement is the most crucial step of SMT assembly. Here engineers place the components on the solder on the PCB. Earlier, companies used old-fashioned ways to place elements on PCBs. Now, advanced technology gives us machines to perform the task.

Reliable PCB manufacturers use machines that can pick and place components. The process saves ample labor hours for the manufacturer and takes the help of automation.

You can also speed up the whole SMT assembly process. Companies can produce multiple batches of PCBs using this automated technology. Machines also don't get tired and always keep working at full throttle. You can also forget about mistakes and misplacements that happen with humans.

Engineers can program machines to place components on predefined locations on the PCB.

Manufacturers do thorough inspection and verification of the component placement. It's crucial to check the correctness before reflow soldering.

(Printed Circuit Board with SMD & IC mounted part on board)

9: Correct Reflow Soldering

The reflow soldering attaches the components on the PCB permanently. The PCBs move through an industrial oven at very high temperatures. The heat melts the solder paste, which runs around the placed components.

The PCBs then move through a conveyor belt through coolers. Solidifies the solder paste and fixes the components in their places efficiently.

Two-sided PCBs need a bit more work for reflow soldering. It would help if you did it on both sides using the stencil placement method. Manufacturers first reflow the team with fewer components. Then they attend to the other side of the PCB.

A correct reflow profile is vital to guarantee that there is no damage. It finds discrepancies in the parts due to overheating and disqualified solder joints.

This step ends the PCB SMT assembly process. From here, the PCB moves on to the next stage of assembling. It starts with manual checks to ensure everything is in the right place and appropriately secured. After that, the PCB can go for through-hole component placement.

A PCB can go through both SMT and through-hole assembly. The designers choose the assembly process based on the application and components.

(Technological process of soldering and assembly chip components on pcb board. )

Conclusion

SMT assembly is not very complicated and commonly used by PCB manufacturers. But you need to have the right knowledge about the process. Our article will help you know all about the SMT assembly. You also got to learn the most important considerations. We hope the information will help you make quality PCBs without errors.

You can also order your custom PCBs from our company. We specialize in SMT assembly and through-hole technology. Our company manufactures custom PCBs meeting your exact specifications and design.

Contact us to know more about our ordering process.