Trace Design for Bump-on-Trace (BOT) Assembly

Abstract

A bump-on-trace (BOT) interconnection in a package and methods of making the BOT interconnection are provided. An embodiment BOT interconnection comprises a landing trace including a distal end, a conductive pillar extending at least to the distal end of the landing trace; and a solder feature electrically coupling the landing trace and the conductive pillar. In an embodiment, the conductive pillar overhangs the end surface of the landing trace. In another embodiment, the landing trace includes one or more recesses for trapping the solder feature after reflow. Therefore, a wetting area available to the solder feature is increased while permitting the bump pitch of the package to remain small.

What is claimed is: 
     
         1 . A structure comprising:
 a substrate; and   a landing trace on the substrate, the landing trace having a first side and a second side opposite to the first side, the landing trace having a plurality of indents extending into the first side in a plan view, the second side being free of indents in the plan view.   
     
     
         2 . The structure of  claim 1 , further comprising a solder feature over the landing trace, the solder feature extending into the plurality of indents. 
     
     
         3 . The structure of  claim 2 , wherein solder feature is in physical contact with the plurality of indents. 
     
     
         4 . The structure of  claim 2 , further comprising a conductive pillar over the solder feature, the conductive pillar overlapping with the plurality of indents in the plan view. 
     
     
         5 . The structure of  claim 4 , wherein a width of the solder feature is greater than a width of the conductive pillar. 
     
     
         6 . The structure of  claim 4 , wherein a width of the landing trace is less than a width of the conductive pillar. 
     
     
         7 . The structure of  claim 1 , wherein the plurality of indents have a comb pattern in the plan view. 
     
     
         8 . A structure comprising:
 a substrate; and   a landing trace on the substrate, the landing trace having a first sidewall and a second sidewall opposite to the first sidewall, the first sidewall having a plurality of indents in a plan view, an entirety of the second sidewall being a planar sidewall.   
     
     
         9 . The structure of  claim 8 , further comprising a solder feature over the landing trace, the solder feature filling the plurality of indents. 
     
     
         10 . The structure of  claim 9 , wherein a width of the solder feature is greater than a width of the landing trace. 
     
     
         11 . The structure of  claim 9 , wherein the solder feature is in physical contact with the second sidewall of the landing trace. 
     
     
         12 . The structure of  claim 9 , further comprising a conductive pillar over the solder feature, the conductive pillar overlapping with the plurality of indents in the plan view. 
     
     
         13 . The structure of  claim 12 , wherein a width of the solder feature is greater than a width of the conductive pillar. 
     
     
         14 . The structure of  claim 8 , wherein the plurality of indents have a comb pattern in the plan view. 
     
     
         15 . A structure comprising:
 a substrate; and   a landing trace on the substrate, the landing trace comprising:
 a first portion; 
 a second portion; and 
 a third portion connecting the first portion to the second portion in a plan view, a first sidewall of the first portion being collinear with a first sidewall of the second portion in the plan view, a second sidewall of the first portion being collinear with a second sidewall of the second portion and a second sidewall of the third portion in the plan view, the first sidewall of the third portion having a plurality of indents in the plan view, an entirety of the second sidewall of the third portion being a planar sidewall. 
   
     
     
         16 . The structure of  claim 15 , wherein the plurality of indents have a comb pattern in the plan view. 
     
     
         17 . The structure of  claim 15 , further comprising a solder feature over the third portion of the landing trace, the solder feature overlapping with the plurality of indents in the plan view. 
     
     
         18 . The structure of  claim 17 , wherein the solder feature is in physical contact with the plurality of indents. 
     
     
         19 . The structure of  claim 17 , further comprising a conductive pillar over the solder feature, the conductive pillar overlapping with the plurality of indents in the plan view. 
     
     
         20 . The structure of  claim 19 , wherein the conductive pillar is in physical contact with the solder feature.