Pcb design and manufacture

Smarter PCB design can help cut manufacturing costs

Saving money, time and effort is always a key part of successful product development, but often achieving these savings can be challenging for designers who are reluctant to compromise quality for cost. We look at some of the ways savings can be made through effective and efficient PCB design.

Effective PCB Design Layout

Careful planning of the PCB layout and assembly process is one of the most critical parts of a product development cycle and a significant amount of due diligence/consideration needs to be applied in order to avoid costly performance and/or manufacturing issues.

Let’s say you have a great product and circuit performance is excellent but you’ve neglected assembly considerations. This could lead to low manufacturing yields; potentially high field failure rates meaning that your great product may be priced out of the market very quickly with a significant amount of the products profit margin consumed in re-work.

The assembly considerations are many and we’d like to think our contract assembler is capable of handling our product but small considerations can make a big difference. BOM optimisation, limiting values, limiting part numbers per side, placement shadows, the list is significant but let’s consider for a minute a taboo subject for designers: Design for Re-work.

 

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Design for re-work

Should I consider design for re-work? You should if you target high quantity continuous annual production and particularly on a product where the profit margin varies quarter to quarter due to supply chain fluctuations. Talking to your assembler, understanding their re-work process and applying some consideration at the PCB design stage can pay huge dividends during production and in any RMA Process (Return Merchandise Authorisation), you might be contractually obliged to carry out.

Engage with your PCB fabricator
Working closely with the PCB fabricator is a great way to ensure your design is optimised for your design process, for their fabrication process and for final assembly. Talk about board stack up, consider long term production and material availability; are there any supply issues on the horizon because you don’t want to have to re-qualify sensitive circuits if the supplier needs to change materials mid production.

Communicating and agreeing design principles in advance gives the PCB fabricator sufficient time to resolve any issues and look for solutions before you hit NPI (New Product Introduction) and production ramps up.

Design rules & manufacturers reference designs
Many would think that once the manufacturing stage is reached it should be all plain sailing, sadly this is where costs can often spiral. Not following design rules can result in numerous board manufacture changes and iterations.

Silicon suppliers often provide reference PCB designs for a particular area of a circuit. Depending on the support they are offering they may dictate the reference design is replicated in full. This is not always practical as the reference design usually has had little consideration for mass production and might not even be geometrically compatible with your product. Talk to the Silicon supplier. Establish the criticality of the circuit areas. Work on compromises. Do this early as these circuits can often have lengthy qualification processes.

Design to IPC standards in conjunction with your assembler’s own process insights.

Panelisation of a PCB
Multiple PCBs on one panel enables all of them to be processed at the same time, instead of separately. Not only are boards manufactured like this, they are assembled and shipped on a single panel. The considerations are twofold:

Firstly, at PCB fabricator stage you can utilise standard panels better.  The more PCBs on one panel, the more cost effective it becomes.

Secondly:  For assembly, the more ‘circuits’ on a panel the better, as the machine can ‘step and repeat’ place each circuit. Benefits of this are machine loading and inspection

There is a benefit to be had from producing panels with multiple different boards on them but you need to consider the final production requirements, potential re-work and PCB fabricator circuit ‘x-outs’. You could end up with an inventory imbalance. This can also strain part number loading for an insertion machine. 2 lines in parallel might be better than 1. Assess and talk to your manufacturer.

Other considerations include rotation of the same board to optimise PCB panel space. So, for example if you have irregular shaped boards this is a great way to minimise PCB material scrap. The assembly issue you might face here is an overall increase in insertion time as the machine is performing twice as many rotations.

Its quite common to specify the direction you want your PCB panel to travel through the assembly process but if you have multiple rotations of the same board on one panel, then inconsistent soldering from one product to another can occur. You need to consider clearance for these issues at either side of a device at PCB design stage. Establish this early in the design phase whilst it is easier to implement.

Continuity of partnerships
If any of your design phases require outsourcing; Design, Supply chain, PCB fabrication and Assembly then if can be beneficial to work with the same partner for as many of those processes as possible. But equally knowing enough about your chosen outsourcing partner and their capabilities is also critical. Talk to them relay your concerns, establish design rules as early as possible, risk assess any necessary compromises and agree on regular business reviews

 

For more information about Quadra’s PCB services and how we can help you with your next PCB design project contact design@quadrasol.co.uk.

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