Method and apparatus for reducing stresses applied to bonded interconnects between substrates
View Patent ↗A method ( 200 ) is provided for reducing stresses applied to one or more bonded interconnects ( 106 ) of a substrate ( 103 ) and a PCB (Printed Circuit Board) ( 104 ). The method comprises the steps of coupling ( 204 ) a compound ( 108 ) on a top surface of the substrate, wherein the compound has the property of expanding when a heat profile is applied thereto, coupling ( 206 ) a cover ( 102 ) to the PCB that overhangs at least a portion of the compound, and applying ( 208 ) the heat profile to the compound and optionally the cover and/or PCB. More than one apparatus implementing the method is also included.
1. A method for reducing stresses applied to one or more bonded interconnects of a substrate and a PCB (Printed Circuit Board), comprising the steps of:
coupling a compound on a top surface of the substrate, wherein the compound has a property of expanding when a heat profile is applied thereto;
coupling a cover on the PCB so that it overhangs at least a portion of the compound;
applying a double-sided adhesive between the compound and a top surface of the substrate at respective perimeter portions, before coupling the cover, leaving voids (i) below the compound and above the top surface of the substrate interior to the perimeter portions and (ii) above the compound and below the cover; and
applying the heat profile to at least the compound and the double-sided adhesive thereby causing the compound to expand such that the compound removes the voids (1) below the compound and above the top surface of the substrate and (2) above the compound and below the cover.
2. The method of claim 1 , wherein the substrate comprises a surface mount IC (Integrated Circuit), and wherein the one or more electrically bonded interconnects comprise one or more solder bumps coupled between an electrical pad of the bottom surface of the surface mount IC and a corresponding electrical pad on a top surface of the PCB.
3. The method of claim 1 , wherein the compound comprises an epoxy resin.
4. The method of claim 1 , wherein the applying the double-sided adhesive comprises: applying the double-sided adhesive to the compound for coupling to the top surface of the substrate.
5. The method of claim 1 , wherein the applying the double-sided adhesive comprises: applying the double-side adhesive to edges of the top surface of the substrate for coupling to the compound.
6. The method of claim 1 , wherein the cover comprises a shield electrically coupled to the PCB for reducing EMI (Electromagnetic Interference) radiated by the substrate, and for reducing EMI entering the shield.
7. The method of claim 1 , wherein the portion of the cover overhanging the compound has rigidity sufficient to reduce stresses applied to the one or more electrically bonded interconnects.
8. The method of claim 1 , wherein applying the heat profile to at least the compound and the double-sided adhesive comprises applying the heat profile with a reflow oven.
9. The method of claim 1 wherein coupling the cover on the PCB further comprises coupling the cover on the PCB so that the cover is attached to the PCB and the cover overhangs at least a portion of the compound.