How Are Double Sided SMD Boards Assembled? Full Process and Comparison

turkey PCBA

We make thousands of boards every week, we know what’s involved in the assembly of all types of boards. So if you’re considering a board for your projects, we thought we’d share an overview of the production process and considerations with you in advance.

 

If you’re unsure about any particular part of the process then certainly get in touch with us. Otherwise, we hope the following outline helps improve your understanding of how double sided SMD boards are assembled.

 

How are double sided SMD boards assembled? It’s very simple. First, assemble and solder one side and then, flip it over to do the other side. When the solder paste is applied to the other side the melting point needs to be a bit lower. So it doesn’t affect the flip side. Then it needs to be run through pick-n-place and vapour phase soldering again.

 

The Difference Between Single and Double Sided Assembly Boards?

Both these PCBs are widely used in different types of electronics. Starting with computers, smartphones, radio controls to other everyday consumer electronics, PCBs are an integral part of the electronic equipment we use in our everyday lives. However, single and double-sided PCBs have different uses and are manufactured a bit differently as well.

 

Single side PCBs are part of many different types of electronics while double-sided PCBs are generally used in more advanced technologies. Depending on the need, output and cost, manufacturers choose the type of PCB.

 

Single-sided PCBs usually has conductive metal and components mounted on only one side of the board. Conductive wiring, generally of copper, is used to connect through the other side. Double-sided PCBs are a bit more complex. They have components mounted on two sides and the wiring crosses over both sides. It is difficult to produce but its uses outweigh the cons and the labour-intensive process.

double side PCBA

PCB Assembly and Manufacturing Process

There are various stages that form part of the assembly and manufacturing process. The solder paste needs to be applied, then the components will be placed onto the board, then soldering, review and testing. All these steps are carefully performed to ensure the best possible quality in the final product. Here’s more information on what each step entails:

 

Solder Paste

This is the first step of the assembly process. This paste needs to be applied to those sections of the board which will be soldered. Generally, these are the component pads. The solder paste is a mixture of small grains of solder and flux. This can be deposited into a particular location using a process similar to the printing process.

 

Then a solder screen is used to place it directly on the board and at the correct position. A runner pushes across the screen ejaculating small amounts of paste on to the board. Since the screen is generated from the PCB files, it has holes in exactly the same locations as the component pads on the boards.

 

Pick and Place

Next, is the pick and place. It is referred to as a machine that helps put the components together with the board. Once the board with the solder paste is ready, it is run through the machine. The machine already has the components loaded into it. It will use dispensers to position the components in their respective area on the board.

 

The components will be held together due to the tension of the solder paste. In some assembly process, small dots of glue are also used. However, that is a practice usually reserved for wave soldered boards. Practicality suggests that using glue makes any kind of repair work difficult. However, some glues are made to degrade during the soldering process.

 

Soldering

Now that the paste is added and components have been placed on the board, it’s time to get them soldered. This is done by passing them through the soldering machine. Some boards are also passed through a wave soldering machine in this part of the process, but that is not widely used in surface mount assembly. The solder paste is given a miss when wave soldering is used. Reflow soldering is more common than wave soldering in contemporary manufacturing.

 

Review

This step is also known as inspection. After the boards have been soldered, they are inspected. For surface mounted assemblies, it is not possible to perform a manual inspection. The automatic optical inspection is more practical in this regard. Machines generally inspect the boards to detect joints, component placements and if the right components have been placed.

 

Testing

After the inspection, the boards are tested to ensure that they’re in proper working condition. As a result, they’re tested in numerous ways. There’s a wide range of instruments used to test the boards including an analogue multimeter, oscilloscope, digital multimeter (DMM), frequency counter, pulse generator, etc.

 

Feedback

Finally, to ensure that the entire process remains true, the feedback from the current batch is reinstituted into the process. This helps keep the process and the components on track to ensure an efficient process.

The process is inspected to find errors and any failures detected during these steps are reinvestigated. The inspection stage is the ideal time for finding issues. As a result, defects can be detected rapidly and corrections reincorporated.

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Manufacturing Difficulties and Risks

PCBs form the main backbone for the electronics that they’re incorporated in. As a result, when the board malfunctions, it affects the entire device. That’s why we’re constantly checking our production process to ensure we minimize any of the difficulties that many other PCB manufacturers struggle with.

 

Errors can also be due to regular wear and tear or manufacturing defects. But in the case of manufacturing defects - predominantly produced by less reputable sources, companies should be identifying the errors or gaps and address them. Here are a few of the most common issues faced in production if you don't have the kind of quality control systems installed that we do.

 

Burnt Circuit Board

During the manufacturing and assembly process, the board is exposed to varying degrees of temperature. Some are very high. So high, that they can burn the board. Each component of the board has its own durability and breaking point. As a result, if there’s not enough space on the board, it might burn the board.

 

Poor Component Manufacturing Quality

Poor manufacturing quality is referred to as a variety of quality issues that happen during the assembly. Generally, issues such as connection troubles, bad solder or loose components.

Another risk if the proper care isn’t taken during soldering is if there’s residual flux. Flux is used during soldering and can damage components if it’s left behind on the board. When selecting a PCB manufacturer to work with you need to ensure they have quality control processes in place to mitigate against these issues, if in doubt, get in touch with us to ensure a quality checked board every time.

 

Effect on Costs

This has always been a question when it comes to manufacturing PCBs. Do we go with single sided or double sided boards? Which one costs less? However, answering that is easy. But the main question should be which one costs less for you.

Single sided boards cost less invariably simply because there’s less to do. Double-sided boards fit more components and there’s two sides fitted with components and then soldered. As a result, it’s obvious that double-sided boards will be more expensive.

However, what do you do when your needs are more acute towards a double-sided board and a single sided board just won’t do? That’s why you need to consider which one costs less in your case. Cost management is an essential part of ensuring an efficient process. More errors or defects mean more wastage and more costs, especially since double-sided assembly is more tricky.

 

Cost Comparison

It’s difficult to compare the actual cost of the two boards without knowing the exact setup, so it’s worth contacting us for a quote.

Both the boards are made up of the same material, same insulator and conductor. The main difference between the two is the conductor placement and thru-holes on each board.

However, there are three main categories which decide the costing - Primary, Secondary and Overhead. Here’s an overview of what components fall in each category:

Primary or Fixed Production Costs Secondary or Dependent Costs Overhead Costs
Board Size Tooling Facility
Number of PCBs produced in a production run Layout – trace design, hole size, and hole count Labor – salaries and benefits
Number of layers beyond double-sided Lamination Equipment
Lead time Change needed from mechanical drill type to laser drill type Raw materials
Hose size and count Quality assurance Chemical processes
Material type and thickness Via fill Wastewater treatment
Layout Fabrication Regulatory permits
Finish Cost of delays due to design or fabrication changes

 

Advantages of Double Sided SMD Boards

There are two main advantages that a double-sided SMD board provides over a single sided board:

 

  1. 1. Since the board has two sides to mount components, there is a higher density of components. This means that the board can carry more components but without congesting the space since there are two sides. As a result, this makes the process of laying tracks easier.
  2. 2. The second advantage is that there’s increased heat dissipation due to the added layer of copper. During the etching process, the copper is removed to create tracks but then reinserted instead of leaving it out completely.

Common Uses for Double-Sided SMD Boards

Single-sided PCBs are generally used in a wide variety of electronics and applications, including camera systems, printers, radio equipment, calculators, and much more.

 

Similarly, double-sided PCB is also used in a wide spectrum of electronic products including lighting systems, vending machines, amplifiers, car dashboards, and many more.

PCB Assembly

 

Conclusion

In conclusion, both single sided and double sided are important - but in different applications. Their uses are different since both boards are built in different manners. Similarly, their costing is different due to the same reason. Based on the application, cost and other factors, a manufacturer can decide on a single sided or double sided board.

If you’re not sure which board you need, then get in touch with us here at RayPCB and we’ll be happy to talk through your requirements, provide the best method for your needs and ensure you get quality manufactured PCB boards.