The quest for the third LV circuit is gated behind the quests for Polyvynil Chloride and SMD Components, suggesting that they are necessary ingredients (which they actually aren't). The questbook is a little misleading here, because at no point are SMD components necessary. I suggest not using the quest for them to gate the circuits, and instead present them as an optional efficiency improvement.

This has been brought up several times in the Discord chat. Refined circuits require polyethylene or PVC for plastic substrates, so there’s absolutely nothing stopping you from making SMD components alongside refined circuits for the maximum efficiency.

This is by design, and we don’t want people to stick to primitive components. SMD components stay relevant during the entire pack.