Thermal solder writing eutectic bonding process and apparatus

A process for attaching integrated-circuit chips to a substrate by soldering, the process comprising the steps of:

• dispensing a precise quantity of solder in solid wire form from a wire spool;
• feeding the wire solder toward one of a plurality of desired locations at which integrated-circuit chips are to be attached to a substrate;
• holding an end portion of the solder wire in the desired location;
• simultaneously heating the end portion of the wire with hot gas from a hot gas injunction system, to melt the end portion and write the desired quantity of solder onto the desired location;
• precisely placing an integrated-circuit chip over the quantity of solder at the desired location;
• heating the integrated-circuit chip, and with it the underlying quantity of solder, with hot gas from at least one hot gas injection systems;
• reflowing the quantity of solder beneath the integrated-circuit chip, as a result of the step of heating the chip, to form a continuous layer of solder between the chip and the substrate;
• allowing the solder to cool, to complete a reliable electrical and thermal bond between the chip and the substrate;
• and
• repeating the foregoing steps at each of the desired locations at which other integrated-circuit chips are to be attached, whereby chips may be positioned in close proximity to each other for improved performance at high frequencies.

A process for attaching integrated-circuit chips to a substrate by soldering, the process comprising the steps of:

• positioning a liquid solder reservoir over one of a plurality of desired locations of the substrate at which integrated-circuit chips are to be precisely attached;
• applying a controlled pressure to the liquid solder in the reservoir, to eject a drop of the solder from a nozzle attached to the reservoir;
• simultaneously heating the drop of solder as it leaves the nozzle, with a hot gas injection system, to keep the solder in liquid form as it is deposited on the substrate;
• precisely placing an integrated-circuit chip over the quantity of solder at the desired location;
• heating the integrated-circuit chip, and with it the underlying quantity of solder, with hot gas from at least one hot gas injection systems;
• reflowing the quantity of solder beneath the integrated-circuit chip, as a result of the step of heating the chip, to form a continuous layer of solder between the chip and the substrate;
• allowing the solder to cool, to complete a reliable electrical and thermal bond between the chip and the substrate;
• and
• repeating the foregoing steps at each of the desired locations at which other integrated-circuit chips are to be attached, whereby chips may be positioned in close proximity to each other for improved performance at high frequencies.

A process for attaching microwave or millimeter-wave integrated circuit (MMIC) chips to a substrate, the process comprising the steps of:

• dispensing a precise quantity of solder in solid wire form from a wire spool, wherein the solder is an alloy of metals including gold;
• feeding the wire solder toward one of a plurality of desired locations at which MMIC chips are to be attached to a substrate;
• holding an end portion of the solder wire in the desired location;
• simultaneously heating the end portion of the wire with hot gas from a hot gas injection system, to melt the end portion and write the desired quantity of solder onto the desired location;
• precisely placing a MMIC chip over the quantity of solder at the desired location;
• heating the MMIC chip, and with it the underlying quantity of solder, with hot gas from at least one hot gas injection systems;
• reflowing the quantity of solder beneath the MMIC chip, as a result of the step of heating the chip, to form a continuous layer of solder between the chip and the substrate;
• allowing the solder to cool, to complete a reliable electrical and thermal bond between the MMIC chip and the substrate;
• and
• repeating the foregoing steps at each of the desired locations at which other MMIC chips are to be attached, whereby MMIC chips may be positioned in close proximity to each other for improved performance at high frequencies.

A process for attaching microwave or millimeter-wave integrated circuit (MMIC) chips to a substrate by soldering, the process comprising the steps of:

• positioning a liquid solder reservoir over one of a plurality of desired locations of the substrate at which MMIC chips are to be precisely attached;
• applying a controlled pressure to the liquid solder in the reservoir, to eject a drop of the solder from a nozzle attached to the reservoir;
• simultaneously heating the drop of solder as it leaves the nozzle, with a hot gas injection system, to keep the solder in liquid form as it is deposited on the substrate;
• precisely placing a MMIC chip over the quantity of solder at the desired location;
• heating the MMIC chip, and with it the underlying quantity of solder, with hot gas from at least one hot gas injection systems;
• reflowing the quantity of solder beneath the MMIC chip, as a result of the step of heating the chip, to form a continuous layer of solder between the chip and the substrate;
• allowing the solder to cool, to complete a reliable electrical and thermal bond between the MMIC chip and the substrate;
• and
• repeating the foregoing steps at each of the desired locations at which other MMIC chips are to be attached, whereby chips may be positioned in close proximity to each other for improved performance at high frequencies.

Apparatus for attaching integrated-circuit chips to a substrate by soldering, the apparatus comprising:

• a wire dispensing mechanism, including a spool for holding wire solder and a wire feed device, for dispensing a precise quantity of solder from the spool;
• a tool for holding a dispensed portion of the solder wire in place at each of a plurality of desired locations at which integrated-circuit chips are to be attached to a substrate;
• a first hot gas injection heater system positioned near the tool for holding the wire solder in place, to heat and melt the dispensed solder wire at each of the desired locations in turn, thereby depositing a desired quantity of solder onto each desired location;
• a pick-and-place tool, for precisely placing an integrated-circuit chip over the quantity of solder at each successive desired location as soon as the solder has been dispensed at that location;
• and
• a second hot gas injection heater system positioned near the pick-and-place tool, employed to heat the integrated-circuit chip and the underlying quantity of solder and thereby to reflow the solder and form a continuous layer of solder between the chip and the substrate.

Apparatus for attaching integrated-circuit chips to a substrate by soldering, the apparatus comprising:

• a liquid solder reservoir, including a reservoir heater, an inlet for pressurized gas for applying a controlled pressure to the solder in the reservoir, and an outlet nozzle through which drops of liquid solder are dispensed, to provide a precise quantity of solder at each of a plurality of desired locations at which integrated-circuit chips are to be attached to a substrate;
• a first hot gas injection heater system positioned near the reservoir nozzle, to heat the dispensed solder drop at each of the desired locations in turn, thereby depositing the desired quantity of solder onto each desired location;
• a pick-and-place tool, for precisely placing an integrated-circuit chip over the quantity of solder at each successive desired location as soon as the solder has been dispensed at that location;
• and
• a second hot gas injection heater system positioned near the pick-and-place tool, employed to heat the integrated-circuit chip and the underlying quantity of solder and thereby to reflow the solder and form a continuous layer of solder between the chip and the substrate.