Fabrication of a high resolution, low profile credit card reader and card reader for transmission of data by sound

A method for fabricating a magnetoresistive sensor from a silicon wafer having a rough side and a polished side, comprising the steps of:

• masking the rough side of the silicon wafer with parallel strips of tape spaced to be substantially equidistant from one another;
• scribing the polished side of the silicon wafer with a first set of substantially parallel scribe lines spaced substantially equidistantly, said first set of parallel scribed lines being substantially perpendicular to said parallel strips of tape;
• cleaving the wafer along every other scribe line in said first set to produce a plurality of silicon bars having straight cleaved edges perpendicular to the polished side;
• coating the plurality silicon bars with a permalloy to cover the rough side and said cleaved edges;
• scribing the coated silicon bars on said rough side with a second set of scribe lines substantially parallel to and spaced substantially equidistantly from edges of adjacent strips of tape;
• cleaving the bars along said second set of parallel scribe lines to produce silicon blocks, each block having a strip of tape extending lengthwise substantially down a center of a top surface thereof;
• removing the strip of tape from each block and cleaving each of said blocks along remaining scribe lines from said first set to produce a plurality of magnetoresistive sensors for use in scanning a credit card, each sensor having an active region along a respective coated cleaved edge.

A method for fabricating a credit card reader from a silicon wafer having a rough side, a polished side and a flat edge, comprising the steps of:

• masking the rough side of the silicon wafer with parallel strips of tape spaced to be substantially equidistant from one another;
• scribing the polished side of the silicon wafer with a first set of substantially parallel scribe lines spaced substantially equidistantly, said first set of parallel scribed lines being substantially parallel with said flat edge and substantially perpendicular to said parallel strips of tape;
• cleaving the wafer along every other scribe line in said first set to produce a plurality of silicon bars having straight cleaved edges perpendicular to the polished side;
• coating the plurality silicon bars with a permalloy using ion beam deposition to cover the rough side and said cleaved edges;
• scribing the coated silicon bars on said rough side with a second set of scribe lines substantially parallel to and spaced substantially equidistantly from edges of adjacent strips of tape;
• cleaving the bars along said second set of parallel scribe lines to produce a plurality of silicon blocks, each block having a strip of tape extending lengthwise substantially down a center of a top surface thereof;
• removing the strip of tape from each block and cleaving each of said blocks along remaining scribe lines from said first set to produce a plurality of magnetoresistive sensors, each sensor having an active region along a respective coated cleaved edge;
• and
• connecting at least one of said magnetoresistive sensors to a circuit having a power supply and a fixed resistor.