Double-Sided Plate Through(DSPT) Printed Circuit Board(PCB)

What is a Double-Sided PCB?

A double-sided PCB has circuit traces on both sides. These faces connect with the help of the plated holes. In this board, the conductive copper components can be mounted on both sides. It allows the traces to cross with each other. It results in circuits with higher density with no need for point-point soldering. The lines, holes, and paths in this PCB can connect to various components electrically. 

It is one of the most commonly used and the most popular PCB as it helps produce complex circuits. This circuit has a wide range of higher technology applications and electronics applications. In any of the applications, a single sides PCB is used. But in the case of higher circuit complexity, there is the need for double-sided complexity. 

One of the impressive advantages of this board is its flexibility and complex circuits. Some of the additional advantages of these double sides boards include:

1. It provides the extra layers for adding more components and thus increases the circuit's density. It results in extra room for connections.
2. Since there is more space, these double-sided circuit boards use complex circuits. Thus it fills the gap of the demanding need in electronics applications.
3. It also provides a cost-saving option since it uses booths sides of PCB.

Double-Sided PCB Stackup

Stack up of double-sided PCBs is simple and is like the two single-layer PCBs integrated. The conductive layer lies at the top of this double-sided PCB. In the center lies a dielectric layer. It is the base material of PCB. The bottom layer consists of another conductive layer. Copper, a cost-effective and best conductivity nature, is used in the conductive layer. Various materials make the base or the dielectric layer, including FR-4, polyimide, PTFE, etc. A non-conductive base material acts as an insulator between the two conductive layers. It is necessary to prevent short circuits between the layers when the base layer is metal, so a dielectric layer adds to create insulation.

In addition to the base and conductive layers, silkscreen, solder mask, and surface finish layers are also present. PCBs with these layers often provide extra benefits. It prevents oxidation and corrosion of the copper layer by protecting it. As a result, the conductive layer lives longer. Solder masks also prevent unwanted connections from forming. On a PCB board, the silkscreen labels the components.

Types of Double-Sided PCB

Double-sided PCB is classified as follows:

1. 1. Double-Sided Rigid PCB
2. 2. Double-sided Flexible PCB
3. 3. Double-sided High Tg PCB.
4. 4. Double-sided Rigid-flex PCB
5. 5. Double-sided Metall Core PCB.
6. 6. Double-sided Heavy Copper PCB.
7. 7. Double-sided High-frequency PCB
8. 8. Double-sided impedance control PCB

Double-Sided PCB Thickness

The typical thickness of PCB is 1.57mm, the standard size. While there are some factors that impact the thickness of PCB. Some of them are as follows:

• Copper thickness
• Board Materials
• Operating Environment
• Signal types
• Type of vias

Advantages of Double-Sided PCB

Some of the advantages of Double Sided PCB include:

• Increases the density of the board with an additional layer for assembling components. 
• The extra space enhances PCB flexibility and allows complex circuits to be designed.
• Smaller boards reduce costs during the fabrication process and assembly of the PCB. 
• Temperature extremes and humid atmospheric conditions do not affect performance. 
• Their open structure contributes to their high reliability and safety.
• PCBs with dual sides have a longer life expectancy.
• They have a wide range of applications in many industries.
• If required, you can reduce the size of the PCB board as it uses both sides.

Disadvantage of Double-Sided PCB

• The double-sided PCB is not an idea for conducting the heavy current in the wires as the copper wires heated up. Thus the PCBs should be of high quality.
• A double-sided PCB is hard to manufacture as the design of this board is quite complex. 
• There is a high risk of overheating while soldering the components. 

Applications of Double-Sided PCB

Many electronics use the double-layer design because of its flexible nature. Some of its application includes:

• Power Supplies
• Hard Drives
• Power Conversion
• Printers
• Vending Machines
• Traffic Systems
• Car Dashboards
• HVAC systems

Double-Sided PCB Manufacturing Process

There is a copper coating on both sides of this double-sided PCB board. In addition, there is an insulating layer positioned in between these coatings. Vias ensures the proper circuit connection between both sides. The manufacturing process of double-sided PCB includes:

Substrate

The very initial step of the manufacturing process is the substrate. Fiberglass makes the substrate as it provides effective robustness. This also provides strength to the board. 

Copper Layer

For this particular layer, the manufacturer uses copper foil or full-on copper. It also depends on the board type and requirement. This layer's basic aim is to effectively transmit the electrical signal within the board. 

Solar Mask

This layer's major purpose is to protect the copper layer. It ensures no short circuit if the circuits come in contact with a conductive environment. The solder mask is a mixture of flux and solder. The PCB board with soldering requires this paste. These components' paste could be deposited in the desired location using a similar process to the printing process. 

Silkscreen

The manufacturer places this silkscreen on the component side of the PCB, where there are logos, symbols, numbers, and more. The screen is placed on the board in the correct position. PCB files generate this screen. Thus it contains all the holes in precisely a similar place to that of pads of components on board.

Preparation

Now, the manufacturer prepared the materials. Next, they drill the board using a CNC machine. The drilling technique for this double-sided PCB differs from that of a single-sided PCB. It uses the through-hole method. Next, they use a CNC machine to create the component drill and through-hole plating. The tension of the solder mask held the components together. Some processes also included the dots of glues. However, the use of glue makes the repairing task challenging. Wave soldered boards primarily use this technique.

Soldering

After placing the mask and components on the board, the next step is to solder the components. A soldering machine carried out this process. Some PCB solderings include wave soldering but are not common in surface mount assembly. The reflowed solder is one of the common and basic types of soldering.

Review and Testing

This is the inspection process which usually takes place after the soldering process. The manual inspection is quite challenging for surface-mounted assemblies. Therefore, the automatic optical review is common in this process. The automated machines detect the joints and components' placement. After the completion of the inspection process, the testing process checks the boars to ensure it's properly working. Thus, numerous ways are followed to test the board. The testing instruments include an analog multimeter, digital multimeter, oscilloscope, pulse generator, frequency generator, counter, etc.

Double-Sided PCB Assembly Process

PCBs with double sides are constructed similarly to those with single sides. For example, a circuit board can have laminated on both sides, but there are some exceptions. 

The substrate is the material that forms the base of the double-sided PCB. Fiberglass epoxy resin is the primary substrate. A PCB board's base material determines whether it's a Flexible PCB or a Rigid PCB. 

Copper foil lamination on both sides of PCB substrate is common in double-sided PCBs. 

In addition to the copper foil on both sides of the board, a solder mask protects the rest of the PCB. The silkscreen is above the solder mask. As opposed to adding characters and symbols to the board, silkscreen is mainly used to describe what the board does. 

The layers of a single-sided PCB are the same as those of a double-sided PCB; the only difference is that the layers appear on both sides rather than just one.

In summary, the step-by-step process of double-sided PCB assembly includes:

• Solder Paste Printing
• Checking
• Pick and Place
• Soldering
• Checking Soldering Effect
• Similarly, for the bottom side:
• Print the Bottom side
• And follow the same steps as before

Difference Between Single-Sided and Double-Sided PCB

Single-sided PCB is the type of PCB where the conductive copper and the components are mounted on only one side. At the same time, there is conductive wiring on the other side of the board, while the Double-sided PCB contains traces on both sides with bottom and top layers. Single PCB is simple in design and consists of various layers, including a protective solder mask, substrate layers, conductive layer, and silkscreen. 

While in double-sided PCB, the design is a bit more complex and thus does not require the point to point soldering. Single-sided PCB has a wide range of applications in electronics, while double-sided PCB is mainly used in advanced and high technology applications.

Rule for Double-Sided PCB Design

One of the primary aims of any PCB manufacturer is to create the perfect and practical design per the customer's requirement. The logical and physician side of any PCB design requires proper management and proper checking. There is a specific rule for checking the design of PCB. Some of the essential things that need to be studied include:

1. 1. Polygon Connect Style
2. 2. Solder Mask Expansion
3. 3. Routing Via Style
4. 4. Electrical Clearance
5. 5. Component Clearance
6. 6. Routing Width

The ten design rule for efficient and effective PCB design includes:

Get the right grid

Make sure to use the same grid spacing across all your components. Multi-grid layouts may seem attractive, but with additional thought, it can avoid spacing difficulties, and maximize the use of boards. Make use of the different package sizes available for many devices. Further, polygons play an essential role when adding copper to boards, and a board with multiple grids is likely to suffer from polygon fill discrepancies, making things harder for you.

Keep trace lengths as short and direct as possible

The rule applies even if it means readjusting the track lengths at specific points on the layout. This is because impedance and parasitic effects will always limit your system's performance, especially in analog and high-speed digital circuitry.

Use power planes whenever possible to manage power lines and ground distribution

Many PCB design software packages offer pours on the power plane as an easy and quick option. A good amount of copper is used to make standard connections, which allows power to flow as effectively and efficiently as possible with negligible impedance or voltage drop and also enables good ground return paths. You should run multiple supply lines on the same board, and remember that a large ground plane can reduce cross-talk between adjacent layers if it runs over a large area of one layer.

Place related test points and components together  

In this case, place the bypass capacitors and resistors directly adjacent to an opamp using discrete components. Testing and fault-finding are also made more accessible, as this helps with track lengths.

Use panels to replicate large boards several times

The cost of prototyping and manufacturing will decrease if you select a size that works with your manufacturer's equipment. First, lay out the board as a single panel. Next, find out what size panel your board house prefers. Finally, repeat the design multiple times within the preferred panel size as soon as your design rules have been corrected. 

Integrate your component values

The discrete components you choose for your design could also have a higher or lower value and work. Consolidating the fewer traditional values can simplify the BOM. In addition, having the PCB based on required device values will make the stock decision more accessible in the long run.

Have a Design rule check (DRC) as often 

DRC on PCB software isn't a quick task, but it can save a lot of hours, especially on complex designs. It also helps to keep the focus on the essential layout choices.

Effective use of silkscreen

Board builders, engineers, technicians, installers, and users can all benefit from the silkscreen by displaying important information. Labels with specifications and test points are straightforward, but components should be arranged logically concerning each other. Silk screening will streamline production and reduce the rework even if the annotation is under components after assembly. 

A decoupling capacitor is a must

Make sure you do not override the limits on component data sheets by escaping the decoupling power lines. Instead, use the capacitor whenever possible, as it is inexpensive and more robust. But while using this capacitor, make sure to keep a neat inventory.

Before submitting the board to the manufacturer, generate date and verify them 

You should avoid misunderstandings when using a free viewer to verify the Gerber file looks the way you envisioned. Most manufacturers will be happy to do this for you. You may even uncover an inadvertent error in fiberglass, resin, and copper.

Double-Sided PCB Price

The PCB price varies based on the layer of the board. The cost of double-sided PCB is higher compared to single-sided PCB. The factors that affect the price of double-sided PCB are:

Materials

The selection of the materials affects the price of the PCB. This selection criteria of the materials depend on various factors based on applications. Some factors include; operating temperature, operation speed, frequency, thermal stability, heat transfer rate, etc. The higher frequency of operation or higher signal speed led to a higher choice of materials. For example, the PCB board designed with polyamide materials increases the cost of the product by three or five times compared to that of FR4 materials. 

Surface Treatment

There are many surface treatment processes for PCB development. Each surface treatment provides unique features, and the price differs accordingly. For example, some finishes acquire higher grades and offer anger shelf life. This adds to the overall cost of PCB production. HASL is one of the low-cost surface treatments. Some of the standard surface treatment options include:

• HASL
• ENIG
• TOP
• IMM Sn
• IMM Ag
• LFHASL
• Flash Gold

Custom or Unique Specification

The custom design of double-sided PCB also affects the price of the product. If the board requires holes less than 0.25 mm, the cost of the board will increase. The higher the hole's density, the higher the PCB board's price. Other custom requirements like on pads, peelable masks, impedance control, edge plating, etc., can increase the cost of the board. Besides, the various quality acceptance standards also affect the board's price. 

Double-Sided PCB Assembly

The price of the PCB increases significantly if your design is double-sided. In double-sided PCB, it uses both sides of the circuit board assembly. Thai leads to the increase in production cost as it included SMT extra soldering, equipment programming, etc. The additional soldering and different skill in double-sided boards increase the price of the board compared to the single-sided board. 

Some of the other factors that determine the cost of PCB are the component types that are used in manufacturing. Some of the essential components in PCB are:

1. 1. Battery
2. 2. Transistor
3. 3. Capacitors
4. 4. Light Emitting Diode
5. 5. Transformer
6. 6. Sensors

Besides, the higher the number of components used in PCB, the higher the production cost. 

Conclusion

The double-sided PCB has a wide range of benefits and offers more flexibility. Thus, the application of this double-sided PCB board is increasing, and many electronic devices use this board. So, check the double-sided PCB specification if you are looking for a PCB for high technological applications. NextPCB is the leading PCB manufacturer. We mainly focus on quality and customer satisfaction. We use the latest technologies and have a skilled workforce who can deal with complex designs and assemblies. Our product includes 5G PCBs, flexible PCBs, HDI PCBs, etc.