I've been trying to come up with a 6 layer PCB layout with microvias. But I cannot think of a cost optimized layer stack, because every manufacturer seems to tell me something different on their website. Since I'm quite confused I hope, someone can shed light on this.
Cost is always the driving factor. Thus, production steps have to be kept at a mimimum. My way of thinking went like this:
- We have 6 layers, so we have to press 2 times anyway.
- Let's name those layers: TO, TC, TI, BI, BC, BO (Top/Bottom Outer/Center/Inner)
- Drilling before the first production step seems to be unneccessary, so buried vias from TI to BI are not an option.
- Drilling is unneccessary for the inner layers. Microvias are laserdrilled and therefore much smaller and faster.
- This results in using microvias from:
- TO to TC
- TC to TI
- BI to BC
- BC to BO
- The final drilling and electroplating is done anyway, so Through Vias from TO to BO are okay too.
Is this the correct way of thinking and therefore the cost optimized layerstack for this kind of problem (given the given information and assuming standard production methods)? If not, which is?
If we take the cost of (1.) into account and not use all-through vias, how will this alter the cost structure?
Thinking about another possibility: Laser drilling from TO to TC AND TI. Is this a cost-viable option?