Partner wisely for high-tech PCB perfection

ES May15 Pg29 to 30 NCAB 2NCAB works hard to ensure it has the right mix of PCB manufacturers on hand to match customer demands for advanced PCBs.

Electronic products are expected to offer more advanced functions while taking up less space. This puts demands on the PCB design and in turn, on the PCB manufacturing process. There are two key factors for the successful production of high quality advanced PCBs; firstly, making the right choices at the design stage and then carefully choosing the factory that can best support the specific technical demands of the project in question.

As components become smaller, so assemblies have to be more densely packed, using smaller features. These specifications often require high density interconnect (HDI) solutions with a greater number of layers, more connections both on the surface and inside the PCB, utilising finer conductor widths and narrower spaces between them. All this leads to a design based on smaller, laser-drilled microvias or blind vias, since normal through hole vias simply wouldn’t fit into the space available.

Experience counts

Technical manager at NCAB Group Sweden, Kenneth Jonsson, explained: “Widespread miniaturisation is putting greater demands on the production equipment at PCB factories. Incorporating several layers of buried vias and/or micro vias requires a number of additional steps, which need to be repeated several times, increasing the degree of complexity and the risk of error. All the geometries are much smaller, which calls for dedicated equipment designed for high-tech manufacturing.

“Many factories do have laser drills, but there aren’t, unfortunately, as many who also possess the appropriate plating equipment and processing experience to enable them to actually make good-quality, reliable HDI boards. That’s why NCAB puts a great deal of time and effort into qualifying and verifying a factory before giving it our seal of approval to manufacture HDI boards for our customers.”

Appropriate equipment

The first consideration in generating micro vias is that of advanced laser drills that can drill blind holes, down to 50µm. Transferring the circuit pattern onto an HDI board is an equally critical operation that calls for the highest precision. To ensure the best possible result, it’s vital that it’s performed in special clean rooms with carefully controlled temperature and humidity levels. Producing HDI boards also requires a specific type of plating line, which involves spraying plating chemicals onto the pads under high pressure to ensure micro vias are properly plated.

NCAB Group carries out a thorough examination of all aspects of a factory’s production processes and equipment when assessing whether or not it meets the demands of high-tech manufacturing.

NCAB?Group COO, Chris Nuttall, explained: “We know that laser drilling equipment is not the start and finish when it comes to HDI production—it’s equally as important to have the right kind of plating equipment, to have the right chemistry, as well as knowing how to handle, control and verify the full plating process. We also look at their experience in this field and their performance—both of which are crucial.”

Currently there are 11 different factories, across China and Europe, which are able to manufacture HDI PCBs for NCAB’s customers.

Chris continued: “We listen and talk to our customers to understand the detail of their designs. We find the right factory for each project, depending on its complexity, volumes and specific demands. And our strategy to develop a secure factory base continues as we always have more than one approved source that can support customers.”

This certainly rings true according to one of NCAB’s customers. Purchasing manager at Hasselblad, Mikael Borg, commented: “Quality and delivery capability are decisive factors for us. NCAB Group’s flora of carefully selected factories ensures that the capacity is always there and they are able to meet the different delivery times and supply the variety of PCBs we need. Thanks to NCAB’s efficient quality control measures on the spot in China, NCAB’s factories always deliver what they promise.”

Quality matters

When it comes to advanced PCB manufacture, it is important to keep the number of production errors to a minimum.

Kenneth Jonsson said: “If a factory returns a 10 per cent rate of failure during each round in the factory, the number of boards scrapped would exceed the volumes they actually deliver. When you consider that the components on the board can cost more than 100 times the board itself, it’s imperative you can rely on board quality. Otherwise, it can be incredibly expensive, if you’re forced to scrap the product at a later stage.”

Prioritise designDesign is also a priority for advanced boards. The margins are tiny with regard to such factors as conductor widths, isolation distances between copper features, impedence requirements, hole sizes and their relation to capture and target lands. All this poses considerable layout challenges.

The design rules should be realistic and adapted to volume production right from the start, since something that might work in a prototype factory, where care is taken to hand-process boards, could lead to major problems in volume production. If there’s enough space on the board, Kenneth also recommends to select components with larger pitches since it reduces the complexity of the board and saves costs.

He said: “There are real differences between producing prototypes and volume production. If you focus on the wrong things from the start, it could jeopardise the entire project if your design can’t be applied in volume production.”

Chris Nuttall concluded: “The advantage of turning to NCAB Group is that we possess skills and knowledge both on design and manufacturing. We know what the factories need in order to successfully deliver quality products and we know which factories are best at fulfilling different types of requirements.”