Cost Tradeoffs in Mechanical Drilling vs. Laser Drilling
Manufacturing costs for PCBs become very important in mid to high volume manufacturing runs. A difference of several pennies per board can add up to a lot of money over time. In deciding to use mechanical or laser drilling, the fixed and variable costs involved need to be thoroughly analyzed.
If you’ve elected to use microvias in your PCB, one aspect to consider is the costs involved in using laser drilling over mechanical drilling. Laser cutters are expensive pieces of equipment, but these systems have a long lifetime. Mechanical drills are cheap, but they wear out quickly and need to be replaced. So when should each of these methods be used?
The right method for placing vias in a PCB mainly depends on size and substrate material, but there is also a cost trade-off that is related to hole density. Standard FR-4 with about 0.1 mm outer diameter via holes can be mechanically drilled with a CNC machine. Laser drilling can still be used for vias with larger diameter. However, there is a cost tradeoff that occurs once the hole density reaches a certain level.
When one examines the production costs associated with mechanical drilling compared to laser drilling, one finds that costs for mechanical drilling tend to outpace laser drilling once the hole density increases past a critical level. Costs increase linearly with the number of vias that need to be placed on a board. Mechanical drilling has lower fixed costs than laser drilling, while laser drilling has lower variable costs.
The primary reason for this cost difference is the tooling costs involved in mechanical drilling. Drill bits wear out and eventually need to be replaced, while laser drilling does not incur these variable costs. At some point, there is a critical hole density where the two drilling methods will have the same total cost. For 0.1 mm microvias, the critical density is about 10 holes per square dm. Laser drilling will have lower total costs at higher via density.
The above cost tradeoff still applies to via-in-pad design. Once vias are placed in pads on a PCB, they either need to be filled with conductive paste and/or tented with a solid layer of conductor to prevent solder wicking through the via. Via-in-pad plated over (VIPPO) structures can also be used to prevent solder wicking.
Whether you plan to fabricate vias in your PCB mechanically or using laser drilling, you need PCB design software with ultra-accurate CAD tools. HGTECH gives you access to the best layout, simulation, rules checking, and deliverable generation tools. Talk to an HGTECH expert today if you want to learn more about how can help you reach your design goals.
