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The cost-optimized PCB – Part 2: Savings potential in pressing, drilling & milling

On the way to a cost-efficient PCB, it is not only the utilization and selection of materials – as described in Part 1 – that play a role. There is also potential for savings in the mechanical machining processes. In particular, the aim is to reduce throughput times for pressing, drilling and milling.

Enabling cost-efficient pressing processes

In terms of cost, the pressing process is primarily influenced by how many production panels the manufacturer can insert into a pressing tool at the same time. The influencing factors here include the choice of materials as well as design aspects, in particular the avoidance of single-ply superstructures. This is because these generally require longer throughput times and cause higher pressing costs.

Another aspect that should be considered is the thickness of the laminates. It is advisable to avoid thin laminates with a thickness of less than 100 µm. This not only minimizes the complexity of the pressing process, but also helps to reduce overall costs.

Further recommendations from the KSG experts:

    • For high process stability, use symmetrical layer structures, the same inner layer thicknesses and the same prepreg types wherever possible.
    • Avoid variance in the materials to ensure the same expansion behavior of the materials in the pressing process.
    • Pay attention to symmetry in the layout and avoid large copper-free areas.

Reduce the number of drilling processes

As with pressing, the time factor also determines the cost of drilling. The more production panels that can be drilled at the same time, the shorter the process time. A dual-capability assembly enables drilling costs to be almost halved. One way to influence this at the design stage is to use the largest possible bore diameter. In this way, a large tool with a correspondingly large spiral can be selected, which is able to drill high packages and therefore several production panels at once. Maximizing the residual rings on the inner layers can also reduce the number of holes required.

Reducing the number of different drilling diameters and borehole types can minimize process complexity.

Supporting efficient milling processes

In order to significantly reduce process times and costs during milling, it is advisable to use standard tools with a diameter of 2.0 mm or 2.4 mm so that the manufacturer can work with a significantly faster feed rate. The dimensioning of the contour tolerances also plays a role. The tolerances should be as large as possible in order to increase flexibility in the production process. The same applies to the positional tolerances of the contour to the drilling and conductor pattern – here too, the recommendation is to aim for generous dimensions in order to optimize the manufacturing processes.

Further recommendations from the KSG experts:

    • Avoid machining clearance areas if you design the delivery panel yourself, as the throughput time must be increased for machining milling compared to contour milling.

Would you like more guidance on PCB design? Then use the design-to-cost recommendations in our Digital Design Compass. In Part 1 and Part 3 of our series of articles, you can also find out where further savings potential can be exploited on the way to cost-efficient PCBs.

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