Study of surface metallization on 3D flexible stack package

Abstract

With the integrated circuit and semiconductor industry develop rapidly, the traditional flat package can't meet the demands for higher performance and lower cost requirements for handheld and portable electronic devices any more in the semiconductor industry. The 3D stacked package technology is a developing method to fit the integrated circuit advanced high-density packaging, which can easily meet the requirement of smaller footprint, thinner profile, multi-function, lower power consumption and lower cost for the smart phones and consumer electronic products. The 3D flexible stack package is a new kind of 3D package which uses special surface metal layer to achieve the interconnection of different dies in the 3D package. The 3D flexible stock package has many advantages over other 3D package (like TSV, FC, etc.). It can achieve the interconnnection between different kinds of functional dies by putting the chip on a flexible substrate to redesign the circuit. Besides, the 3D flexible package can also simplify the packaging process and reduce the production cost. According to these advantages, the 3D flexible can be applied in the field of aerospace and military. The main process of the 3D package is to film the metal layer on a plastic packaging cube by surface treatment technology. Electroless plating (EP) is a better chioce, but for now, EP on the plastic material is not enough mature. The binding force of the plating layer on plastic is not able to be guaranteed. In this paper, the results showed the pretreatment process of electroless plating and the plating environment are the important influence factors to the plating results. By the way of designing contrast test to find the right parameters, like the surface roughness, temperature, is the main method to solve the problems. Although the EP nickle layer can be successfully coated on the surface of plastic cube, the plating effect (the binding force, thickness, thermostability, etc.) can't be made sure. Therefore finding a suited method to test the performance of the nickel coat is also of great importance. This paper primarily focused on the way of the eletroless plating nickle and the method of the coat performance examination, and obtaining some useful technological parameters and reliability data by comparing the experimental results.