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Method for using metallized UV sensitive epoxy to replace lead-based solder paste

IP.com Disclosure Number: IPCOM000101712D
Publication Date: 2005-Mar-16
Document File: 3 page(s) / 789K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for using metallized ultraviolet (UV) sensitive epoxy to replace lead-based solder paste. Benefits include improved functionality and improved throughput.

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Method for using metallized UV sensitive epoxy to replace lead-based solder paste

Disclosed is a method for using metallized ultraviolet (UV) sensitive epoxy to replace lead-based solder paste. Benefits include improved functionality and improved throughput.

Background

      Regulations require all solder paste used in products for

Europe

to be lead free by 2005.

 

      One lead-free solder is an indium-based solder paste. It requires processing temperatures as high as 260 degrees Centigrade to ensure the required surface wetting for the solder paste to wick up the side walls during the reflow process. At this temperature, tin plating begins to melt, creating a problem for soldering components on printed circuit boards (PCBs). An effective solution is required that enables components to be soldered to PCBs without high temperatures during the reflow process.

      The conventional solution is to deposit solder on the PCB using a stencil. Components are placed on the PCB using robotic arms. A reflow oven brings the metal solder to a liquefied temperature, which enables the solder to wick up the walls of the components and secure them to the PCB. The reflow step is followed by visual and computerized inspection.

      The reflow step can take up to 15 minutes per PCB. A faster method is required.

     

      Noise reduction is typically required to ensure the quality of electronic circuits. A conventional solution is to solder a shield fence around components that emit frequency noise (see Figure 1). Additionally, an electromagnetic interference (EMI) shield can be placed over the noise-emitting components (see Figure 2.)

      UV-sensitive epoxy has been used for a number of years in the dental field. Epoxy is well understood and UV light-directing guns are already well designed with excellent reliability in the field.

General description

      The disclosed method is lead-free approach to soldering electromagnetic interference (EMI) shields or other components to motherboards without the use of a reflow oven. UV light is used to fuse a component to a PCB in seconds with UV-sensitive epoxy. Grounding is ensured by using tin alloy or st...