"Classic physics" essentially stopped at the knowledge that a current (from wherever it came from) would draw two metal leaves together. Quantum physics provided the knowledge of what was actually happening at the sub-atomic level, which is where and how solid-state circuitry functions. We would never have developed the transistor without it; an IC chip would be just a collection of thin wires, and would have done nothing.
Your knowledge of IC design was already established when you started using it (assuming you're not older than sixty). The quantum mechanics that dictated the theory behind IC design is about a century old. You may not have needed to be conversant with quantum theory to do your work, any more than I need to be conversant with it to type on this laptop, but your work depended on the established principles developed under quantum theory nonetheless.