As a timid engineer on my first job at an electronics company that designed military equipment, I was thrilled to be invited to a design review meeting. With serious faces, the designers discussed the printed circuit board (PCB) cost breakdown, while I studied the schematics.
Too young to be schooled in military top-down office protocol, the engineer-artist in me had a flash of insight while analyzing the circuitry, and thinking out loud I blurted, "Why is all the circuitry designed in squares and rectangles? The electrons just get jammed up in the corners -- they could travel faster if you designed in circles, and you could also layer them .... " and my voice trailed off to nothing as I noticed that they were all looking at me dumbfounded.
My boss explained patiently, "It's just that we are going into production next week -- too late to change the design now." I nodded meekly, head down, mortified.
This was my first head-on encounter with the reality that functionality in design is limited by its manufacturability. These two aspects of design have everything to do with a PCB cost breakdown.
What Is Entailed in a PCB Cost Breakdown?
To accurately assess PCB cost breakdown, input is needed from many factors, each of which has subcategories and qualifiers. For example, when considering which materials to use, one has to consider what functions the material will perform, and under what conditions? These functions and conditions are further broken down into each material's thermal rating and heat transfer properties, signal transfer performance, and mechanical properties such as ability to withstand vibrational stress and shock.
Formulating a PCB cost breakdown begins with the size of the board and the number of layers. The size of a board will generally be determined by the number of circuits required for the device in which the board will be utilized. The number of layers is decided from:
The loads the circuitry will have to withstand
Whether there will be high-tech components
The number of signal layers (determined from pin density)
What are some of the variables that drive up PCB cost?
Some variables influence the overall PCB cost breakdown more than others, and must be thoroughly analyzed prior to commencing production. These critical variables include:
The Number and Size of Holes in a Board
If the holes are super-thin, they require laser drills. Designs that call for drilling through 10 or more layers, or materials that are hard to drill will increase PCB cost.
The Width of Traces (Signal Conductors)
To avoid transient surges and the threat of overheating, the traces must have sufficient width. Board makers will enlarge the trace width and add extra solder mask to traces that might be prone to high capacity, adding to the PCB cost.
Even if the board itself is small and consists of only one or two layers, custom specifications will always raise the PCB cost breakdown. What drives the cost up for custom boards is whether special tools or production skills are required. For example, metal edging, extra clearance for solder mask, and rounded edges come with an added cost, as does the use of board finishes with higher grades and a longer shelf life. Boards that involve higher frequencies and military-compliant PCBs are going to cost more due to high-grade materials and testing requirements.
Understanding what can affect the cost of a PCB helps control its price
Functionality vs. manufacturability
The traditional PCB cost breakdown has been directed by the manufacturability of its separate parts. When there has been a hard choice between two design options, the ease of manufacturability has more often been the deciding issue due to less cost, rather than optimum functionality.
Recently, however, the advent of additive manufacturing, or 3D printing, is slashing PCB production costs dramatically. Additive manufacturing creates three-dimensional solid objects from a digital file, by laying down successive layers of material. As 3D printing scales up and enters the electronics manufacturing industry, highly efficient functionality in design is gaining a foothold over the old supremacy of manufacturability.
Additive manufacturing is one of many ways to save money during the PCB production process
What is exciting is that with 3D printing. the need for tooling is eliminated - no metal drills or lasers required for vias and heat transfer holes! High-definition trace lines can be built on unlimited numbers of multi-layer boards, measuring up to industry standards of conductivity, strength, thermal stability and dielectric behavior. Single components can be built that have both rigid mechanical strength, and flexibility where bending is required.
In the immediate future, new design freedoms will make their way into mainstream electronics production with the advent of industrial 3D printers. Streamlined functionality and beauty of design will render the old manufacturing limitations obsolete. PCB cost breakdowns will become simplified to choice of materials, the functional requirements of the end application, and creation of digital files.
Calculate the price of design before production
To avoid exceptionally high costs that might stem from unique or custom PCB design requests, designers are wise to calculate the PCB cost breakdown before production. Determining the specifications of the design and the steps required to bring it to fruition with a PCB cost breakdown will prevent hidden cost overruns.
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