Method for forming a microbattery

Abstract

A method for forming a microbattery including, on a surface of a first substrate, one active battery element and two contact pads, this method including the steps of: a) forming, on a surface of a second substrate, two contact pads with a spacing compatible with the spacing of the pads of the first substrate; and b) arranging the first substrate on the second substrate so that the surfaces face each other and that the pads of the first substrate at least partially superpose to those of the second substrate, where a portion of the pads of the second substrate is not covered by the first substrate.

What is claimed is: 
     
         1 . A method for forming a microbattery comprising, on a surface of a first substrate, one active battery element and two contact pads, this method comprising the steps of:
 a) forming, on a surface of a second substrate, two contact pads with a spacing compatible with the spacing of the pads of the first substrate; and   b) arranging the first substrate on the second substrate so that said surfaces face each other and that the pads of the first substrate at least partially superpose to those of the second substrate, where a portion of the pads of the second substrate is not covered by the first substrate.   
     
     
         2 . The method of  claim 1 , wherein, at step a), a plurality of pairs of contact pads are formed on the second substrate, and, at step b), a plurality of substrates each supporting one active element and two contact pads are arranged on the second substrate, a subsequent step of dicing of the second substrate being provided to separate the microbatteries from one another. 
     
     
         3 . The method of  claim 1 , comprising a step of bonding of the first substrate to the second substrate by bonding means resistant to temperatures greater than 100° C. 
     
     
         4 . The method of  claim 3 , wherein said means comprise an electrically-conductive glue connecting the pads of the first substrate to the pads of the second substrate. 
     
     
         5 . The method of  claim 3 , wherein said means comprise solder paste connecting the pads of the first substrate to the pads of the second substrate. 
     
     
         6 . The method of  claim 3 , wherein said means comprise a non-conductive glue connecting at least some regions of the first and second substrates. 
     
     
         7 . The method of  claim 3 , wherein said means comprises a molded resin layer coating the surface of the first substrate opposite to the active element. 
     
     
         8 . The method of  claim 1 , wherein contact bumps are bonded to the portions of the pads of the second substrate which are not covered by the first substrate. 
     
     
         9 . A microbattery comprising:
 on a surface of a first substrate, one active battery element and two contact pads; and   superposed to the first substrate on the active element side, a second substrate comprising two contact pads with a spacing compatible with the spacing of the contact pads of the first substrate, the pads of the first substrate at least partially facing the pads of the second substrate and being connected to these pads, where a portion of the pads of the second substrate is not covered by the first substrate.   
     
     
         10 . The microbattery of  claim 9 , wherein the first and second substrates are connected by bonding means resistant to temperatures higher than 100° C.