Does thickness really matter?

We were recently contacted by a new customer questioning the quality of our PCBs. It’s the first time in the decade we’ve been doing this, so naturally we were a bit taken aback. His main issue was the thickness. In comparing our boards to some he had recently acquired elsewhere he thought the thicker PCBs from the other supplier were somehow superior. An explanatory email later and any doubts were put to bed, so we thought we’d explain our reasoning here just in case anyone else wonders why we opt for 1.2mm boards over 1.6mm in most cases.

The case against 1.6mm

Most of our PCBs are 50 x 50mm or smaller. At this size the FR4 substrate used for PCBs is very rigid. Certainly tough enough for our purposes.

If we go bigger than 50 x 50mm we consider using the thicker 1.6mm material for extra rigidity, depending on parts placement and how many components are going to form a mounting for the finished build.

So why not use 1.6mm for everything? Save material. ‘But it’s only .4mm!’. Indeed, but dropping that .4mm can save a lot.

Now, to keep things simple we’re going to take the copper, ink and solder out of the equation. We can put it back in later.

Let’s take the aforementioned 50 x 50mm PCB:

- With a 1.6mm substrate we have a total FR4 volume of 50 x 50 x 1.6 = 4,000mm3.

- Take that same board and use 1.2mm and we have 50 x 50 x 1.2 = 3000mm3.

So we use 75% of the material compared to the thicker board, for the same end result with zero disadvantages.

Our PCB deliveries are quite heavy - often over 50KG in total. Let’s pretend none of that is packaging, all FR4. That 50KG delivery becomes 66.6KG for the sake of that extra little bit of thickness. It might not seem much, but 16KG less flying around the globe is a worthwhile saving. And we’ve already saved that 16KG of FR4 at the factory. That's a canny chunk of stuff. Winner.

Any other unexpected advantages of the thinner boards? We think so.

- Over the course of soldering all those lovely holes you’re using less molten material. A tiny amount, but it mounts up.

- Easier to desolder if you have an issue.

- It’s only .4mm, but that can make a difference in tight spots, and could mean the difference between closing that enclosure or pressing up against that oversized cap you bought by mistake.

Any disadvantages?

None we can think of on boards this size.

Make sense? It does to us.

Cheers

Team FD