For standard circuit boards, a PCB manufacturer is given a set of patterns - copper patterns, hole patterns, ink patterns, which are combined into a single circuit board with all the pattern sizes and positions within certain tolerances. Failure to meet a certain size or position with the specified tolerance can be cause for the circuit board to be rejected. If a trace has been defined as an impedance control trace, it is not the trace size which is strictly defined, but rather the impedance. While a nominal trace size will be provided in the Gerber layer, it is understood the circuit board manufacturer can vary trace width, height, and dielectric thickness as long as the final impedance is within tolerance.
Plating Hard Gold onto printed circuit boards is typically done to provide contact points and PCB edge connectors.
Gold contact surfaces are often used on circuit boards with membrane switches which are a technology of choice for industrial, commercial and consumer products. When PCBs will be repeatedly installed and removed electroplated gold is used for edge-connector contacts or as they are more commonly known: Gold fingers. It is difficult to hear the term Gold finger without remembering the villain Auric Goldfinger from the James Bond film of 1964. However, the gold fingers (gold-plated contact pins) found on PCBs are quite unlike Auric’s stubby, fat digits. To begin with, the plating thickness of a PCB gold finger is typically a mere 300 micro-inch. At this thickness the hard gold is expected to survive 1,000 cycles before wear through.
As you might expect, no two applications for aluminum trace circuit boards are the same and most often they are not even similar.
While some customers are investigating frontiers in MEMS (Microelectromechanical systems), others are delving into the inherent superconductive properties at milliKelvin temperatures, while still others are exploiting the radiation response characteristics of aluminum. For the R&D personnel at Omni Circuit Boards, the requests have presented some interesting challenges.
Single source arrangements between companies are often a source of stress for management, supply chain and operations personnel on both sides of the table. Provided it is managed intelligently, the relationship can be long-term and beneficial to both parties. But just a little bad luck or poor management by either side, can quickly escalate into a financial catastrophe.
I have had the good fortune to have had roles on both sides of the single source table, first in purchasing, then in management roles. Initially, the challenge is to find a supplier with the knowledge, equipment and interest to provide materials with specifications far in excess of what is currently available in the market. In some instances, I was asked to find suppliers with the capability to manufacture components with tolerances beyond what our own QC department was able to measure. Depending on the complexity of your requirements, this phase can take months and requires travel to candidate sites to audit capabilities and access the flexibility of their organization. Typically, the virtues which brought you to the site were provided by sales and marketing types whose vision of the company exceeds their abilities. Once you sit at the table with those in the know, you quickly learn not only are they not able to provide what you need, they do not have an interest in pursuing it, much to the chagrin of the sales and marketing types.
One of the more artistic processes in a PCB manufacturing facility is the application of Ident layers, also known as silk-screening.
Silkscreen is normally used on the component side to identify components, test points, PCB and PCBA part numbers, warning symbols, company logos and manufacturer marks. It isn’t uncommon to have silkscreen required for the solder side as well but if you are price sensitive, you need to know the work required to produce two silk-screens is simply twice as much as one.
Silk-screening requires specially formulated inks. Standard colours are Black, white and .yellow. Non-standard colours can be requested but will impact your cost and your lead-time.
Today's computing technology is rapidly outpacing the capabilities of standard, mass-produced printed circuit boards. That's why it was no surprise when the engineers at British Columbia based D-Wave Systems came to us looking for a unique product.
PCB manufacturing facilities routinely perform Electrical Testing with “Flying Probe” testers which are well suited to smaller production runs.
For short runs, the flexibility of quick set-up ensures cost effective Flying Probe tests outperform the lead-time, cost and fixed designs of dedicated test beds. With Flying Probe tests, no fixtures need to be prepared, only data files. Flying Probe tests are able to reveal not only shorts and opens produced by the manufacturing process but have also been known to expose design errors.
One of the more interesting activities routinely associated with PCB manufacturing is the process of assembling multilayer circuit boards.
At any given time 40% of our PCB manufacturing at Omni is producing multilayer circuit boards, so understanding the process is important. Layers of copper foil, prepreg and core material are sandwiched together under high temperature and pressure to produce multilayer assemblies. Pressure is needed to squeeze out air while heat is required to melt and cure the thermosetting “prepreg” adhesive which holds the multilayer PCB together.