Flexible connection for reflow free fine pitch SOP SMT components

As the device miniaturization, the assembly is becoming more and more dense. The current fine pitch package or micro BGA and other forms of interconnection come to a certain limit, which hindering the development of packaging and assembly. high-density assembly and packaging is facing a lot of new challenges. Today, even the most of the fine pitch packages' pitch maintained at around 0.3mm, it is difficult to continue to shrink, because with the pitch further smaller, there will be a series of problems. For example: package reliability to reduce the emergence of lead bridging, solder ball, cold solder joints and other issues. In order to solve these problems, this paper presents a new way of interconnection. The conductive function is achieved by the conductive silicone rubber between the pad on the PCB and the lead of the packaged device. Due to the presence of pressure, the conductive adhesive is deformed and can be contacted from the top to the bottom. This interconnection form may be adapted to all conductive patterns depending on the spacing of the conductive layers. Conductive adhesive in the conductive material is generally carbon, metal, metal oxide, carrying capacity between 800 ~ 2800mA/mm2. The current production of conductive silicone spacing between 0.1 ~ 0.05mm. Through this technology, the size of the packages can be greatly reduced, and the assembly density can be greatly improved. In this study, a new type of interconnection was studied and designed. SOP package, first the conductive silicone layer is connected to the lead bottom of the SOP device , and then the SOP device lead and the solder pad on the PCB are aligned. By using a special design mechanism to make conductive silicone rubber deformed and fixed to achieve this interconnection between leads and PCB solder pad. There are two fixed ways: First, set the hooks on the PCB board, which will fixed the device; second through designing a SMT device (reflow soldering to the PCB) and it secure to achieve required connection. This use of conductive adhesive elasticity ensures a reliable connection between the SOP device leads and the PCB pads. This new design greatly reduces the size of the package meanwhile increasing the density of placement and assembly. It is proved that the connector can be reliably operated in most environments with an operating temperature between -40 and 150 °C and can improve the corrosion resistance, shock and vibration resistance for the package. In addition it can also overcome problems during reflow.