LED PCBs play an important and almost indispensable role in modern life. Whether it is the toys you play with, or the street lights outside your window, LED PCBs are everywhere. A technology based on the integration of ‘Light Emitting Diodes’ or LEDs onto ‘Printed Circuit Boards’ or PCBs, they are an interesting and almost innovative piece of technology, which revolutionized electronics.
Offering a wide range of advantages such as low cost, high efficiency, structural strength and so on, they quickly found their way into a wide range of applications. Indeed, the technology itself has started to undergo transformations, given the research and development underway to make things better. Coming to the design aspect of these LED PCBs, there are several different aspects that are taken into consideration.
Some of the most important are listed out in the points below.
1) Figure out the Ideal Board Design Layout
If there is one step that comes first before anything else, it would be that of the design. There are many different ways in which a circuit can be laid out, meaning that one has to first come to a conclusive one, before the production can begin. The considerations for this in turn, are many, ranging from time constraints and available space in the machine, to material availability and budgets.
2) Ensure Proper Orientation
The term orientation is a reference to the flow of the circuits, from one end to the other. In general, all PCBs have one entry and one exit, or at most a few. The way in which the electricity and data flow, is what is termed as orientation. While a circuit will generally go in one direction at any given time, there is still the issue of organizing the board in a manner that is just as straightforward. In simple words, the circuits and other components being printed on the board need to begin at one end, and stop at the other, in a fairly straight path, rather than being jumbled up.
3) On the Subject of Component Placement
In addition to the circuits and the LEDs, the average PCB has a wide range of components that are integrated into it. For those wondering what they are, they include things like resistors, capacitors, etc. If you are wondering what they look like, they are the many small ‘chips’, ‘cylinders’ and other structures that one sees on a circuit, when any piece of technological hardware is disassembled. These components in turn, need to be placed in such a way that one avoids having them on the solder side of the circuit board, which in turn would rest behind the through-hole plated components.
4.) Avoid Placing Components near the PCB Outline
This is something that helps to better manage the board design, as well as ensure that the existing design is sturdy and reliable. It is important because placing components towards the edge of the PCB might result in the circuits failing in the future, or in other cases, to the dislodging of the components themselves from the base. About the only exception to this are those components which need to be at the edge, such as that of say, sockets.
5) The Placement of Components
A good strategy for efficient component placement, is to ensure that all ‘Surface Mounted Devices’ or SMDs are placed as per SMD PCB design rules. This in turn, is a reference to a set of guidelines that suggest industry practices that are considered the best and effective. Of the many that exist, one of the most important to keep in mind, is that all through-hole or TH components must be placed at the top of the board, in order to reduce the number of steps required for assembly.
6) Avoid Placing VIAs near the End of SMT Pads
The ‘vias’ or ‘vertical interconnect access’, is a feature of circuit boards, which allow for the placement of circuits between two or more layers. In some cases, it may go from the surface to the interior of the board, as in the case of multi-layer PCBs, while others may have the same extending from one end of the board to the other. Typically designed from copper, they are placed in the board after a hole is drilled into the PCB. SMT or ‘Surface Mounted Technology’ on the other hand, is a reference to the method used for placing SMD or ‘Surface Mounted Devices’ that are integrated into the circuit for a variety of functions.
The above is important in order to understand the point being made. Placing vias too close to SMT pads will cause the solder to migrate away from the pad and enter the via space, and end up creating a faulty joint. It is therefore a good idea to avoid it, with a general distance of 0.025 inches or greater, between the via and the SMT pad.
7) Net Width Design & Definition
The design of the board will have a need for a wide range of currents. This variability in turn, will have required the net width of the circuits to vary as well, and which must be kept in mind at all times. While there are many things that come under this subject, it is in general a good idea to have a 0.010 inch width wire for low current analog and digital signals, while those carrying more than 0.3 A of electricity should be wider.
8) Budget & Cost Management Issues
This has to do with the overall budgets and costs, rather than the actual design. Everything has to be managed within a budget, on a personal as well as industrial level. And that certainly holds true in the case of LED PCB design. While there is much that can be said, one of the best ways to go about doing this is to estimate the budget beforehand, create cost estimates and work out something sustainable, before getting started. In addition to this, it is also a good idea to watch out for cost overruns.
As a whole, designers will very likely find these points to be very useful when it comes to managing the design, fabrication and overall management aspect of producing LED PCBs. Done right, they should go a long way in making the process more efficient, effective and affordable for all.