Search
Close this search box.

Understanding Double-Sided PCBs: A Comprehensive Guide

Double-Sided PCB

Various electrical devices frequently use double-sided printed circuit boards (PCBs). A single conductive surface on single-sided PCBs is surrounded by two conducting layers on either side. Each conductive layer is encircled on either side by a solder mask, a copper layer for the circuit, and a dielectric layer. Manufacturers can create traces on each side of a via that cross over one another and connect between layers. Instead of using multi-layer PCB, manufacturers often utilize double-sided printed circuits for goods requiring minimum to maximum circuit complexity and density. This kind of PCB is economical for many uses.

Double Sided PCB Construction

Double-sided printed circuit boards (PCBs) comprise two sides of conductive copper and a layer of insulating material between them. Vias are used to create a secure connection between these two sides. Subsequently, the PCB is populated with components from both sides. There are two processes for double-sided printed circuits: Dry run and Wet Run. The dry run process involves the construction of the PCB in a single pass through the printing press. During the wet run procedure, the PCB is joined to the other side with a die. In the case of double-sided components, both sides need to be soldered to ensure a secure connection. Anything that occurs on the higher side of the PCB will also affect the lower side of the PCB. The only distinction between a double-sided and a flip-side component assembly is the difference in the solder mask’s melting point.

Design Considerations for Double Sided PCBs

Design Considerations for Double Sided PCBs

The only difference between a double-sided PCB and a single-sided PCB is that some layers are present on both sides. The PCB is built on a substrate, an insulating material frequently made of fiberglass or epoxy resin. Depending on the base material used, copper foil is applied to both sides of a double-sided PCB before being covered with a solder mask. A silkscreen is also positioned above the board on both sides to help people understand what it is doing. These layers are the same in a double-sided PCB and a single-sided PCB. A double-sided PCB differs from a single-sided PCB in that layers are visible on both sides instead of just one.

Component Placement and Routing Techniques

Rout with user-friendly modes

No matter how sophisticated, any plan can be easily navigated using various routing strategies. Use the Push, Walkaround, and Stop at First Obstacle techniques to navigate confined locations. Furthermore, you can route with clearance restrictions to view your design requirements and rapidly gauge how effectively a way would function.

Clean Routes with Gloss & Retrace

Create the most beautiful layouts with a gloss engine that shortens route lengths and enhances trace angles. When your design rules change, the Retrace tool refreshes the chosen traces automatically.

Multiple Tracks Route

For signal groups following the same path, route many tracks rapidly and simultaneously. Change the bus spacing, layer, and pattern selection fast using the same push, hug, and cornering modes as single-track routing.

Signal Routing – High Speed

Impedance profiles that determine the trace width for single-end and differential signals based on the material, layer stack up, and current routing layer ensure your high-speed communications’ integrity. It is easy to change the length and delay tuning and fine-tune topologies so that copper traces fit into their assigned areas using complex algorithms, ensuring that nearby signs fly at the same speed.

Modifying Existing Routes

Utilize intelligent tools to quickly and easily edit existing topologies. Automatically push topological objects and smooth the nearest obstacle. Quickly select design objects to update properties.

Component Routing – BGA

The most popular BGA component packages are automatically fanned out with control over the fanout pattern, shape, and track width.

Signal Integrity and Impedance Control

Signal Integrity

It is recommended to maintain short and direct signal path traces. Sensitive signals shall be routed on inner layers and, where feasible, adjacent to or within reference planes. As much as possible, clock lines and other sharp, high-speed signals shall be separated from other traces.

Impedance Control

When sending a signal, the termination impedance should correspond to the source and transmission impedance. This allows the highest possible signal power to be sent to the termination. If the transmission and termination impedances are incompatible, part of the signal will reflect into the trace, resulting in distortion of the incoming signal. Specific communication protocols are more susceptible to interference and degradation than others, so it is essential to understand the specifications for your particular signal.

Manufacturing Process of Double Sided PCBs

The fabrication of double-sided PCBs is a complicated procedure. A two-way PCB is created through many phases with the raw PCB. The many stages of the PCB manufacturing process will be explained in this article.

PCB Circuit Design

The first stage in designing and producing a double-sided PCB is drawing a schematic diagram. Various PCB designing software is accessible online that you can use to create your PCB.

PCB Layout Design

The PCB layout design can begin as soon as the PCB schematic design is finished. The PCB layout can be printed on glossy paper using a laser printer. It is crucial to remember that before top-layer printing, the image from the layout must be reversed to prevent the circuit from being inverted.

DFM Check

The specialists examine the file (PCB Layout File) as part of the DFM check procedure to find and fix any faults and errors. The experts check the trace, layer, hole, pad, and other components to ensure the design is suitable for manufacturing. The circuit board is delivered for manufacturing after the procedure and documentation are complete.

PCB Material Selection

Various substrates are used to make printed circuit boards, or PCBs. FR4, ceramic, iron, aluminum, and other PCB substrates are available to users and PCB makers. Different PCB brands and substrates have other properties, and different substrates offer multiple advantages.

Cutting of Copper Clad Laminate

The board is cut, the sides are sanded, and the corners are trimmed. A double-sided PCB can be built because the board has copper layers on both sides.

Drilling

An automated drilling device receives the circuit board and immediately drills holes. Drill holes in the circuit take different actions. A PCB can have holes of three different types. They’re called vias, PTH holes, and blind and buried holes. The first type is the PTH hole. It’s where the connections between the components are made. It’s also where the inner layers are connected. Double-sided boards don’t have the blind and buried type of holes, so they don’t have an inner layer.

Electroless Copper Deposition Plating

The electroless deposition of copper (Cu) through the holes is an essential step in the production of double-sided printed circuit boards (PCBs) and multi-layer printed circuit boards (MCBs). PCBs with two or more layers typically use plated copper through holes to join conductors between layers.

Photo Imaging and Printing

The process requires creating a film with the circuit design on it. The PCB board is then used to transfer the circuit design using this film. Following the previous technique, the photoresistive coating is applied on the board. Once mechanically hot-rolled onto the board, the film is applied. After depositing the film, the board is prepared to be exposed to ultraviolet light for circuit printing.

Pattern Plating

The client chooses the PCB surface’s copper thickness. Before being electroplated, the copper surface of the panels is activated and cleaned in baths. The entire process is computerized to ensure that each batch or flight of items stays in each tub for the proper period of time. The copper anodes are visible in their sacks. After the copper has been plated onto the board, a thin sheet of tin is applied, which will be used in the subsequent stage of the process when the unwanted copper foil is removed.

Develop and Etch

After that, a developing solution is used to clean the board. During this process, the mismatched photoresist on the board is removed. The hardened portion of the board is then scraped off to create the circuit layout. The circuit’s conductive component is then removed, then the remaining copper. After that, the board is treated with an etching solution. The copper behind the hardened photoresist is undamaged, but the solution removes the extra copper from the board.

AOI (Automatic Optical Inspection)

Inspecting before proceeding further with the etching process is essential, as there is a risk of an open circuit, short circuit, or other issues arising. Automatic Optical Inspection (AOI) is a straightforward test involving cameras to photograph the circuit board. The pictures are then compared to the original design, and any issues are identified. The circuit board is then isolated from the lot.

Solder Mask

A thin polymer coating known as a solder mask is a barrier between two conducting lines, preventing the formation of short circuits. Different colors of the material, including green, white, and blue, are applied to the circuit board before being dried.

Silkscreen

Printed circuit boards (PCBs) are covered with printed labels called silkscreens. Use silkscreens to identify parts and apply the branding. The printed circuit board (PCB) is run through a large-format printer to produce printed labels during this process.

Surface Finish

Copper on the board is susceptible to oxidation and thus cannot remain in its original form for an extended time. Applying a surface treatment to stop the copper from oxidizing is necessary. Customers can access surface finishes, such as Immersion Tin, Immersion Silver, Hasselwhite Finish, OSP Finish, ENIG Finish, ENEG Type, and ENEG Type.

Routing

A cutting machine is used to separate circuits from a panel and cut them into individual pieces.

Probe Test

This is a straightforward test that utilizes many probes. The inspections cover the connections, and electricity is run through them. It determines if the circuit is functioning correctly or not. This stage marks the conclusion of the double-sided PCB manufacturing process. The printed circuit boards are then packed and given to the consumers after this stage.

Assembly and Testing of Double Sided PCBs

SMT(Surface Mount Technology) Assembly Techniques

Dispensing

Installation of a dispenser on the input surface is advised. A water droplet at the input connects the electronic parts to the printed circuit board. A dispenser is sometimes used in front of the inspection equipment and at the end of the production line.

Component Placement

Using a Pick&Place machine, this technique ensures that surface mount components are firmly connected to the designated location on the PCB.

Curing

This makes it easier for the patch glue to melt, ensuring that the components are securely attached to the PCB. The curing oven is used behind the machine installed in the Surface Mount Technology assembly line.

Reflow Soldering

The solder paste must be melted to attach the SMT components to the printed circuit boards using this procedure. The tool that makes this procedure possible on the assembly line is the Reflow Soldering Furnace, which is situated below the placement machine.

Cleaning

This procedure involves cleaning dangerous soldering residues, including flux, off PCBs undergoing SMT assembly. The washing machine acts as the equipment, and since it can be operated at any point along the production process, its location cannot be fixed at any moment.

Inspection

To confirm the precision and superior quality of the welding process, the Welded Board Assembly Quality Test is carried out. The test calls for using AOIs, flying probes, microscopes, online testers, magnifying lenses, etc.

Rework

In this section, we include printed circuit boards (PCBs) that have been found to have a defect. The PCB shall be remanufactured to eliminate the fault. The tools used are soldering iron, and the device shall be positioned along the manufacturing line at the specified position.

Conclusion

The design of double-sided PCBs is similar to that of flexible PCBs and flex PCBs in that it requires the appropriate design software. This software must provide layout tools that enable the user to switch views between layers and define connections between layers rapidly. Additionally, accurate layout tools must be used, as well as component management tools that provide data directly to the production planning tools. The design workflow will be significantly simplified if these features are accessible in a single software. This article gives you a general overview of double-sided PCBs.

Share:

Table of Contents