RF Sensitivity of Multi Chip Package Development by Using Embedded Resistor in Package Substrate

Abstract

Recently, mobile age is blooming and makes change of 21st century. Especially multi chip package – MCP- is located center position of this flash era. Moreover, radio frequency –RF- sensitivity determines the product quality and life, therefore we try to develop the RF sensitivity of MCP in wireless circumstance. In this study, MCP comprised NAND Flash memory, Mobile DRAM, and a substrate, we focused on the substrate, changed substrate design and performance by using resistor embedded into 1 layer of substrate. The purpose of adaption of embedded resistor is in order to control the slew rate of signal channel of DRAM. NiCr thin film was used for the resistor in substrate. NiCr material presents superior temperature coefficient of resistance –TCR- to thick film material. NiCr coated on Cu foil and this foil laminated by conventional substrate manufacturing method. Embedded resistor applied on signal line as 3 kinds; 1. Signal and signal strobe line by 50 Ohm, 2.Signal strobe line by 50 Ohm, and 3. Signal and signal strobe line by 20 Ohm. In case of 3, result showed 0.5 dBm increment of RF sensitivity in full strength mode, also we got the same performance at half strength mode. Embedded resistor formed substrate did not affect the reliability of MCP, from the results of reliability test; pre-conditioning test, thermo-cyclic, temperature humidity, HAST, un-Bias HAST, and hot temperature storage test. This study showed signal waveform of DRAM is significantly effective in RF sensitivity for MCP. Passive component, resistor, made change of slew rate and revealed increase of sensitivity level finally.