Reflowable camera module with improved reliability of solder connections

Abstract

A reflowable camera module has a set of solder joints formed on a bottom surface of the camera module that provide electrical signal and power connections between the camera module and a printed circuit substrate. The solder joints are susceptible to failure caused by shear forces, particularly in corner regions. Additional localized mechanical supports are provided to protect those solder joints carrying power and electrical signals for the camera module. The localized mechanical supports are formed outside of a region containing the solder joints carrying power and electrical signals. The localized mechanical supports may include dummy solder joints formed in corner regions and/or dummy leads used to support the camera module. Solder joint reliability is enhanced without requiring the use of an underfill encapsulant.

1 . A packaged camera module with improved reliability of solder joint connections without an underfill encapsulant, comprising:
 a printed circuit substrate;   a reflowable camera module mounted to the printed circuit substrate, the reflowable camera module including an image sensor, the reflowable camera module including a bottom surface having four corners;   solder joints formed between the reflowable camera module and the printed circuit substrate along a portion of the bottom surface of the camera module, the solder joints providing electrical signal and power connections to the image sensor;   the packaged camera module including additional local mechanical supports exterior to the portion of the bottom surface having the solder joints providing electrical signal and power connections, the local mechanical supports supporting the camera module to the printed circuit substrate to protect the solder joints providing electrical signal and power connections.   
   
   
       2 . The packaged camera module of  claim 1 , wherein the local mechanical supports comprise at least two leads extending over an outer surface of the camera module with the ends of the leads mounted to the printed circuit substrate. 
   
   
       3 . The packaged camera module of  claim 2 , wherein each lead extends across two sides and a top surface of the camera module. 
   
   
       4 . The packaged camera module of  claim 3 , wherein each lead is attached to the printed circuit substrate before plating of the camera module. 
   
   
       5 . The packaged camera module of  claim 3 , wherein there are two leads extending across two opposed edges of the upper surface of the camera module. 
   
   
       6 . The packaged camera module of  claim 1 , wherein the local mechanical supports comprise dummy solder joints formed between the camera module and the printed circuit substrate proximate corner regions of the bottom surface, the dummy solder joints providing additional mechanical support but not providing electrical signal or power connections to the image sensor. 
   
   
       7 . The packaged camera module of  claim 6 , wherein the dummy solder joints comprise dummy solder joints formed in corner regions of the bottom surface via solder balls that are reflowed. 
   
   
       8 . The packaged camera module of  claim 6 , wherein the dummy solder joints comprise areas proximate each corner in which solder paste regions are reflowed. 
   
   
       9 . The packaged camera module of  claim 1 , wherein the local mechanical supports comprises epoxy formed along edges of the bottom surface. 
   
   
       10 . The packaged camera module of  claim 1 , wherein said carrier is a Chip Scale Package carrier. 
   
   
       11 . A reflowable camera module, comprising:
 a Chip Scale Package (CSP) carrier, the carrier defining a rectangular surface area having a first side, a second side, and four corners;   an image sensor mounted to the first side of the CSP carrier;   an optical capping layer having at least one optical lens element covering the image sensor;   solder contact regions formed in a central portion of the second side of the carrier dedicated to provide electrical signal and power connections between the image sensor and a printed circuit substrate after a reflow process; and   each of the four corners of the second side of the CSP carrier having a corner region including at least one dummy solder contact region to provide mechanical support to the solder contact regions dedicated to provide electrical signal and power connections, the at least one dummy solder contact region not providing electrical signal or power connections to the image sensor.   
   
   
       12 . The reflowable camera module of  claim 11 , wherein the solder contact regions formed in the central region are Ball Grid Array (BGA) solder contact regions for a BGA solder reflow process. 
   
   
       13 . The reflowable camera module of  claim 12 , wherein each corner region includes at least one dummy solder ball contact onto which solder balls are formed for a BGA solder reflow process. 
   
   
       14 . The reflowable camera module of  claim 11 , wherein each corner region includes a soldering area. 
   
   
       15 . The reflowable camera module of  claim 14 , wherein each soldering area has a plated metal region onto which a solder paste is deposited. 
   
   
       16 . A method of improving reliability of solder joint connections in a reflowable camera module without using an underfill encapsulant, the method comprising:
 forming solder joints that provide electrical signal and power connections to the camera module via a solder reflow process between a central portion of a bottom surface of a carrier of the reflowable camera module and a printed circuit substrate;   forming additional local mechanical supports outside of the central portion of the bottom surface of the reflowable camera module;   the additional local mechanical support regions protecting the solder joints that couple electrical signals and power from shear forces.   
   
   
       17 . The method of  claim 16 , wherein said forming additional local mechanical supports comprises forming dummy solder joints in corner regions of the bottom surface via the reflow process, the dummy solder joints providing mechanical support but not coupling electrical signals or power to the camera module. 
   
   
       18 . The method of  claim 17 , wherein the dummy solder joints are formed using solder balls. 
   
   
       19 . The method of  claim 17 , wherein the dummy solder joints are formed using a solder paste extending over a corner region. 
   
   
       20 . The method of  claim 16 , wherein said forming additional mechanical supports comprises forming at least two leads across over the surface of the camera module and attaching the ends of each lead to the printed circuit substrate. 
   
   
       21 . The method of  claim 16 , wherein said forming additional mechanical supports comprises forming epoxy beads proximate corner regions. 
   
   
       22 . A reflowable camera module, comprising:
 a Chip Scale Package (CSP) carrier, the carrier defining a rectangular surface area having a first side, a second side, and four corners;   an image sensor mounted to the first side of the CSP carrier;   an optical capping layer having at least one optical lens element covering the image sensor;   solder contact regions formed in a central portion of the second side of the carrier dedicated to provide electrical signal and power connections between the image sensor and a printed circuit substrate after a reflow process; and   at least one lead extending over an outer surface of the camera module and having two lead ends extending out from the camera module to permit the lead ends to be attached to a printed circuit substrate to provide additional lateral mechanical support to protect solder joints between the printed circuit substrate and the camera module.   
   
   
       23 . The camera module of  claim 22 , wherein there are at least two leads, each lead extending over the outer surface of the camera module and having lead ends extending out to permit the lead ends to be attached to the printed circuit board to provide lateral mechanical support to corner regions. 
   
   
       24 . The camera module of  claim 23 , wherein each lead is attached conformably to two sides and a top surface of the camera module. 
   
   
       25 . The camera module of  claim 22 , wherein the at least one lead is coupled to ground.