Printed Circuit Boards (PCBs) are crucial to the operation of any electronic device, be it a high-tech mobile phone or a cheap Electronics play. The PCB is the most overlooked and expensive part of the BOM during the product development cycle. Reducing the size of the PCB will not only reduce the size of our product but will also bring down manufacturing costs in most cases because PCB costs much more than any other component used in a circuit. Reducing the dimensions of a printed circuit board (PCB) is a common goal in electronics manufacturing, but doing so presents a unique set of challenges. In this piece, we’ll go over the Design Techniques for shrinking PCBs, including a discussion of the benefits and drawbacks of each approach.
Multi-Layer PCB for Reducing Track Space and Component Spacing
Routing takes up most of the real estate on a PCB. One or two layers of PCB board are used at most in the prototype phases, during the testing of the circuit. However, a double layer circuit board is typically required when the circuit is constructed with SMD (Surface Mount Devices). When the board is designed with two layers, all components can be reached easily from the top, and there is room for routing the traces. If the number of board layers is raised from the standard two to, say, four or six, the available surface area of the board will once again expand. However, there is a disadvantage. The testing, repairs, and rework of a circuit become extremely complicated if it is built with two, four, or even more layers.
Therefore, the only way to achieve numerous layers (primarily four layers) is to thoroughly test the prototype version of the board. Designing the same circuit on a smaller board also requires less time than doing so on a larger single- or double-layer board.
It is common practice to use thicker traces for high current pathways, such as Power traces and Ground return path fill layers. In four-layer PCBs, the outermost and innermost layers can be used for the higher current traces and the lower current paths and signal layers can be used for interior routing. A 4 Layer PCB is depicted in the picture below.
However, there are costs and benefits to consider in the abstract. Multilayer PCBs are more expensive than single-layer ones. As a result, upgrading from a single- or double-layer board to a four-layer PCB requires careful consideration of the financial implications. However, the height of the board may be significantly altered if the number of layers is increased.
Managing the Thermal Issues by changing Copper Thickness
PCB’s thermal control is an especially helpful feature for high-current circuit designs. A PCB trace’s heat dissipations and resistance rise when a large current passes through it. A major benefit of the PCB, however, is the ability to make heat sinks, in addition to the dedicated thick traces for managing high current paths. Therefore, increasing copper layer thickness can be used to reduce board size if the circuit design requires a sizable quantity of PCB copper area for thermal management or allocates large spaces for high current traces.
The IPC2221A stipulates that designers must account for the overall trace area when determining the minimum trace width for current paths. Traditionally, the copper layer width of PCBs was 1Oz. (35um). However, the copper can be made thicker if necessary. Simply increasing the thickness to 2Oz (70um) would result in a 50% reduction in trace width while maintaining the same present capacity. In addition to this, the PCB-based heat sink can benefit from a copper layer of 2Oz. The heavier copper capability, from 4Oz to 10Oz, is also a possibility.
As a result, the PCB can be made smaller by raising the copper thickness. Let’s check out how useful this turns out to be. PCB trace width can be determined with the help of an online tool, like the one shown in the picture below.
The value of current that will flow through the trace is 1A. The thickness of the copper is set as 1 Oz (35 um). The rise of the temperature on the trace will be 10 degrees on 25 degrees Celsius ambient temperature. The output of the trace width as per the IPC2221A standard is-
Now, in the same specification, if the copper thickness is increased, the trace width can be decreased.
Component Package Selection
In circuit construction, component choice is crucial. In electronics, you can find components that are identical but come in a variety of various casings. A simple.125-watt resistor, for instance, may come in a number of various packages, including 0402, 0603, 0805, 1210, etc.
The larger 0805 or 1210 resistors and non-polarized capacitors with greater clearance than usual are typically used on the prototype PCB because they are simpler to handle, solder, replace, and test. However, this strategy produces an extremely large quantity of playable area. Components can be switched to a smaller package with the same rating and board area can be compressed during the manufacturing process. The components can be packaged more compactly.
However, the problem is which offer should be selected. Smaller SMD packages than 0402 are impractical to use because the production’s standard pick and place machines may not be able to manage them.
The lower power level of the smaller components is another disadvantage. Less current is required for smaller containers than the 0805 or 1210, and the 0603 is one such example. This means that picking the right parts requires some serious thought. When smaller packages cannot be used to reduce PCB size, the package footprint and component pad can be edited to achieve the best feasible reduction. The creator can try to make more space by adjusting the footprints. Because of design constraints, the usual footprint is a generic one that can accommodate multiple package revisions. The footprint of 0805 containers, for instance, is designed to accommodate a wide range of component configurations. Differences in production capacity are to blame for the discrepancies. Manufacturers’ specifications for the same 0805 package used to vary from machine to machine. As a result, the standard container sizes are slightly excessive.
The pad area can be reduced manually by using the component datasheets to modify the footprint.
Since SMD-based electrolytic capacitors appear to have smaller diameters than the through-hole components with the same rating, they too can be used to reduce the height of the board.
New Age Compact Connecters
Connectors are another element that takes up a lot of room. The connections take up more room on the board, and the pads in the footprint are bigger because of them. If the current and voltage ratings allow, switching connector kinds can be very helpful.
Manufacturers of connectors like Molex and Wurth Electronics (among others) routinely stock numerous sizes of each connector type. As a result, picking the correct dimension can reduce expenses and conserve real estate on the circuit board.
Resistor Networks
Series pass resistors are almost always necessary in microcontroller-based architecture to prevent damage to the microcontroller from excessive current flowing through the IO pins. As a result, the number of resistors used in a series pass configuration must be greater than 8, and often greater than 16. With that many resistors, the PCB quickly becomes unwieldy. Resistor networks are an effective tool for dealing with this issue. Four or six resistors’ worth of room could be freed up by using a 1210-based resistor network. The picture below depicts a 1206-packaged, 5-watt resistor.
Stacked Packages Instead of Standard Packages
Many circuit layouts need more than two MOSFETs or transistors to accomplish their goals. Using stacked packets may save more room than adding up individual transistors or Mosfets.
Multiple components can be found in a number of different choices. There are other options for saving board area, such as dual Mosfet or quad MOSFET packages that only require as much room as a single Mosfet.
These methods are universally applicable. This results in less board area being needed, and as a bonus, sometimes the combined cost of these components is less than if they were used separately.
The aforementioned considerations represent a potential solution for shrinking PCBs. PCB size, complexity, and expense are all factors that must be considered when making important design decisions. The correct route to take is one that is chosen in light of the intended use or circuit architecture.