Method for applying bonding agents to pad and/or interconnection sites in the manufacture of electrical circuits using a bonding agent injection head

A method of applying solder paste mixtures to pad sites in the manufacture of electronic circuits using a paste injection head comprising the steps of:

• applying a mask to a carrier, said mask having cavities at chip pad application sites on the carrier;
• lowering said paste injection head to contact a surface of the mask, said paste injection head comprising a wiping guide, a blade which cooperates with the wiping guide to form an elongate nozzle slit, and an evacuation path in the paste injection head;
• applying pressure to a solder paste in the injection head on one side of a cavity;
• moving the paste injection head across the cavity so as to deposit solder paste in the cavity, wherein the evacuation path in the paste injection head is located ahead of the nozzle slit in a direction of travel of the paste injection head across the mask to let air out of the cavity as the cavity is filled with the solder paste;
• and
• releasing pressure when the paste injection head contacts an opposite side of the cavity;
• retracting the paste injection head;
• and
• heating the carder to evaporate a paste flux and reflow solder deposited in the cavity to form solder balls within the cavity and projecting above the mask.

A method of applying an electrically conductive adhesive to pad sites in the manufacture of electronic circuits comprising:

• applying a permanent mask with cavities around conductive pads on a carrier;
• said conductive pads defining chip pad attachment sites;
• contacting a stencil to the permanent mask, said stencil having holes congruent with cavities in said permanent mask;
• depositing a volume of electrically conductive adhesive through the stencil with an injection head to fill cavities to a level of the stencil, said injection head comprising a wiping guide, a blade which cooperates with the wiping guide to form an elongate nozzle slit, and an evacuation path in the injection head said depositing comprising moving the injection head across the cavities so as to deposit the conductive adhesive in the cavities, wherein the evacuation path in the injection head is located ahead of the nozzle slit in a direction of travel of the injection head across the stencil to let air out of the cavities as the cavities are filled with the conductive adhesive;
• removing the stencil from the mask;
• and
• curing the electrically conductive adhesive.

A process for making a circuit board, comprising the steps of:

• producing a board having a wiring pattern including copper contacts on at least one surface;
• coating the board with a mask;
• photo-lithographically forming blind holes through the mask at the copper contacts;
• providing an elongate dispensing nozzle containing a bonding agent in paste form, said providing the elongate dispensing nozzle comprising the steps of:
• providing a wiping guide,
• providing a blade which cooperates with the wiping guide to form an elongate nozzle slit, and
• providing an evacuation path in the dispensing nozzle;
• moving the dispensing nozzle into contact with the mask adjacent to the blind holes;
• pressurizing the bonding agent paste inside the dispensing nozzle;
• moving the dispensing nozzle across the mask over the blind holes in a direction generally perpendicular to the elongate direction of the nozzle slit wherein the evacuation path in the dispensing nozzle is located ahead of the nozzle slit in the direction of travel of the dispensing nozzle across the mask to let air out of the blind holes as the blind holes are filled with the bonding agent paste;
• and
• depressuring the bonding agent paste within the nozzle;
• and moving the nozzle away from the board.