Structure to accommodate increase in volume expansion during solder reflow
AssigneeInternational Business Machines Corporation
InventorsDavid Vincent Caletka, Krishna Darbha, Donald W. Henderson, Lawrence P. Lehman, George Henry Thiel
Life of this patent
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Abstract
Solder balls, such as, low melt C4 solder balls undergo volume expansion during reflow. Where the solder balls are encapsulated, expansion pressure can cause damage to device integrity. A volume expansion region in the semiconductor chip substrate beneath each of the solder balls accommodates volume expansion. Air-cushioned diaphgrams, deformable materials and non-wettable surfaces may be used to permit return of the solder during cooling to its original site. A porous medium with voids sufficient to accommodate expansion may also be used.
Claims31
A connection structure between an electronic device and a substrate therefor, comprising:
- at least one conductive pad on said electronic device;
- at least one conductive pad on said substrate;
- a solder ball positioned between said at least one conductive pad on said electronic device and said at least one conductive pad on said substrate;
- insulating material surrounding and in contact with said solder ball to enclose said solder ball;
- and
- at least one volume expansion region adjacent a portion of said solder ball to accommodate volume expansion of said solder ball during reflow.
A connection structure comprising:
- an electronic device having a array of electrical contacts;
- a substrate for said electronic device having an array of electrical contacts matching the array of electrical contacts on said electronic device;
- solder balls respectively positioned between each of the said electrical contacts of said array of electrical contacts of said electronic device and each of the corresponding electrical contacts of said array of electrical contacts of said substrate;
- insulating material filling the space between said semiconductor chip and said substrate between each of said solder balls so as to enclose each of said solder balls;
- a hole through each of the said electrical contacts of said substrate beneath the respective solder balls positioned thereon;
- and
- an expansion region formed in said substrate open to each said hole to accommodate volume expansion of said solder balls during reflow.
A method of interconnecting electronic devices using reflow of encapsulated solder comprising:
- forming a volume expansion region adjacent to said solder having volume dimensions sufficient to accommodate enough of the volume expansion of said encapsulated solder during reflow so as to prevent damage;
- and
- applying heat to said solder to cause solder reflow to the liquid phase and expand into said volume expansion region.
A method of attaching an electronic device having an array of contact pads to a substrate having a matching array of contact pad sites, comprising:
- forming volume expansion regions in said substrate beneath each of the said contact pad sites of said array of contact pad sites;
- forming substrate contact pads at each of the said contact pad sites of said array of contact pad sites of said substrate;
- forming vias through each of said substrate contact pads to the respective ones of said volume expansion regions in said substrate;
- attaching said electronic device to said substrate with solder balls respectively connecting each contact pad of said array of contact pads of said electronic device to each substrate contact pad of said substrate;
- enclosing each of said solder balls with an insulating material;
- and
- reflowing said solder balls such that the volume expansion of said solder during the liquid phase expands into said volume expansion region.
Dependencies are inferred from the claim text.