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How to design a cheaper PCB?

This article explains a couple of most important things what you should worry about while designing a layout for the cheaper PCB.

1. Design your layout with the minimum number of layers.

In some cases if you spend more time on component placement and routing, you can decrease the number of copper layers. If it’s possible to use only two layers instead of four, without losing quality of your layout, this could save you a lot of money. It isn’t always possible but you should consider it. The Table 1. shows how the average PCB price increases with adding more layers if all other PCB parameters is the same.

Table 1: How the average PCB price increases with adding more layers to the layout

This calculation doesn’t include set-up costs. Calculation was made for 10 pieces, 100 x 100 mm PCB board size, 1.6 mm thickness, FR4, surface finishing HAL Lead Free, 35um finishing Cu thickness, top and bottom solder mask and silkscreen, >0.2 mm minimum hole size, >4/4 mil minimum track width/spacing and delivery board in pieces.

2. Design your layout with the minimum surface area

Decrease a surface area/dimensions of your PCB as much as you can. In the first place, price depends on a layout surface area. With the ideal component placement and routing you can achieve minimum dimensions of the board or/and PCB panel.

3. How the PCB price depends on the copper thickness?

As you already know, there are some standard copper (Cu) thicknesses which you can order from the PCB manufacturers. Cu thickness can be expressed in:

• millimeters (mm),
• micro meters/microns (um), 1000 um is 1 mm
• inches (inch), 25.4 mm is 1 inch
• mils (mil) – 1000 mil is 1 inch
• ounces (oz) – If 1 oz of copper is pressed flat and spread with the same thickness over 1 square foot (1 foot = 12 inch) area, the resulting copper thickness is 1.37 mil. In short, 1 oz of copper corresponds to 1.37 mil.

Table 2 shows how the average price of the PCB increases in percentage (column: Increase in PCB price in %) when the copper thickness increases. Also table data presents how to convert from ounces to inches, millimeters or microns. Table rows consist of some standard copper thicknesses which manufacturers of the boards offer.

Table 2: How the average PCB price increases when copper layer thickness increases

This calculation doesn’t include set-up costs. Calculation was made for 10 pieces, 100 x 100 mm PCB board size, 1.6 mm thickness, FR4, surface finishing HAL Lead Free, two copper layers board, top and bottom solder mask and silkscreen, >0.2 mm minimum hole size, >4/4 mil minimum track width/spacing and delivery board in pieces.

4. How to set minimum clearance/spacing?

Many manufacturers have different PCB prices for different minimum spacing. In your routing rules for minimum clearance (spacing) between the different net objects, set maximum dimensions with which you can properly finish your layout. Price is not the same if you set 3 mil, 4 mil or >4 mil for the minimum clearance and spacing. For example if minimum clearance is 4 mil, price is 10% higher than in the case if minimum clearance is set to >4 mil. If minimum spacing is 3 mil, the price is three times higher than in the case if minimum clearance is >4 mil. See table below.

Table 3: How the average PCB price increases when minimum clearance/spacing decreases

This calculation doesn’t include set-up costs. Calculation was made for 10 pieces, 100 x 100 mm PCB board size, 1.6 mm thickness, FR4, surface finishing HAL Lead Free, 35um finishing Cu thickness, two copper layers board, top and bottom solder mask and silkscreen, >0.2 mm minimum hole size and delivery board in pieces.

5. Increase minimum via and pad hole sizes and set them all with the same size

Many manufacturers have different PCB prices for different minimum via and pad hole sizes. In your routing rules for minimum via and pad hole sizes, set maximum dimensions with which you can properly finish your layout. Some PCB manufacturers offer better board price if layout have a smaller number of different via and pad hole sizes. Price is not the same if you set 0.15 mm, 0.2 mm or >0.2 mm for the minimum via and pad hole sizes. For example if minimum via and pad hole size is =0.2 mm price is 5% higher than in the case if minimum via and pad hole size is set to >0.2 mm. If minimum via and pad hole size is =0.15 mm, the price is 15% higher than in the case if minimum clearance is >0.2 mm. See table 4.

Table 4: How the average PCB price increases when minimum via and pad hole sizes increases

This calculation doesn’t include set-up costs. Calculation was made for 10 pieces, 100 x 100 mm PCB board size, 1.6 mm thickness, FR4, surface finishing HAL Lead Free, 35um finishing Cu thickness, two copper layers board, top and bottom solder mask and silkscreen, >4/4 mil minimum track width/spacing and delivery board in pieces.

6. Save money by ordering your boards as prototype

If you need only a few pieces of PCBs (for example: for prototype or development) you should consider ordering your boards as prototype. Some manufacturers offer to make PCBs as prototypes. In this case, manufacturers collect layouts from different customers and put it on one panel and don’t charge the tooling. The manufacturers put a lot of constraints for this type of order. For example: PCB thickness, copper thickness, minimum hole size, minimum clearance, dielectric material type, finishing type, board dimensions…

7. Panelize your layout on your own

If your layout is prepared for the mass production, PCBs should almost always be delivered as panel. Almost all manufacturer’s of the PCBs charge panelization. If you do it by yourself you can save setup costs of the layout panelization.

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