Modularized die stacking system and method

A flex circuit connecting an upper IC element and an integrated circuit die in a circuit module, the flex circuit comprising;

• first and second outer layers;
• and
• first and second conductive layers, between which there is an intermediate layer, the first and second conductive layers and the intermediate layer being interior to the first and second outer layers, the second conductive layer having demarked first and second flex contacts, the first flex contacts being accessible through first windows through the second outer layer and the second flex contacts being accessible through second windows through the first outer layer, the first conductive layer, and the intermediate layer, the first flex contacts in electrical connection with the upper IC element and the second flex contacts in electrical connection with the integrated circuit die.

A circuit module comprising:

• a first CSP having first and second lateral sides and upper and lower major surfaces and a set of CSP contacts along the lower major surface;
• an integrated circuit die having a set of die connective sites connected to a pair of flex circuits;
• each of which pair of flex circuits having a first conductive layer and a second conductive layer, both said conductive layers being interior to first and second outer layers, and demarcated at the second conductive layer of each flex circuit there being upper and lower flex contacts, the upper flex contacts being connected to the set of CSP contacts of the first CSP and the lower flex contacts being connected to the die connective sites of the integrated circuit die and a set of module contacts.