Vent blocking on vented ball grid arrays to provide a cleaner solution barrier

A method of mounting a commercial off-the-shelf (COTS) ball grid array (BGA) package configured for use with a no-clean flux to a printed wire board (PWB), said package comprising a substrate and an array of solder balls on the bottom of the substrate, an integrated circuit (IC) die and other internal electrical devices with associated internal solder attachments and conductors on top of the substrate in electrical contact with the solder balls through vias in the substrate, a lid and a plurality of discrete beads of a first adhesive on the substrate around both the IC die and other devices that attach the lid to the substrate and form pressure relief vents, said lid having a polarity through-hole formed therein outside the adhesive beads towards one corner of the package, said through-hole being an indicator of the orientation of the BGA package, the method comprising:

• applying a continuous bead of a second adhesive around the perimeter of the COTS BGA package to seal the gap between the lid and substrate, said continuous bead and discrete beads defining a channel through the pressure relief vents to the polarity through-hole:
• reflow soldering the BGA package to the PWB at an elevated temperature using solder flux, said IC die achieving elevated temperature pressure relief through the pressure relief vents along said channel and out the polarity through-hole;
• applying a seal to plug the polarity through-hole;
• and
• washing the PWB and the BGA package in an aqueous cleaner solution to remove flux residues on the PWB, said continuous bead of adhesive and said seal sealing the BGA package to form a cleaner solution barrier that prevents the solution from contacting the internal conductors.

A method of mounting a commercial off-the-shelf (COTS) ball grid array (BGA) package configured for use with a no-clean flux to a printed wire board (PWB), said package comprising a substrate and an array of solder balls on the bottom of the substrate, an integrated circuit (IC) die and other internal electrical devices with associated internal solder attachments and conductors on top of the substrate in electrical contact with the solder balls through vias in the substrate, a lid and a plurality of discrete beads of a first adhesive on the substrate around both the IC die and other devices that attach the lid to the substrate and form pressure relief vents, said lid having a polarity through-hole formed therein outside the adhesive beads towards one corner of the package, said through-hole being an indicator of the orientation of the BGA package, the method comprising:

• applying a continuous bead of a second adhesive around the perimeter of the BGA package to seal the gap between the lid and substrate, said continuous bead and discrete beads defining a channel through the pressure relief vents to the polarity through-hole:
• reflow soldering the BGA package to the PWB at an elevated temperature using solder flux, said IC die achieving elevated temperature pressure relief through the pressure relief vents along said channel and out the polarity through-hole;
• applying a pre-seal to cover the polarity through-hole;
• applying a third adhesive over the pre-seal that seals to the lid;
• washing the PWB and the BGA package in an aqueous cleaner solution to remove flux residues on the PWB, said continuous bead of adhesive and said seal sealing the BGA package to form a cleaner solution barrier that prevents the solution from contacting the internal conductors;
• and
• removing the pre-seal and third adhesive to reopen the polarity through-hole and said channel.