Patent Application
20120279521
Disclosed embodiments relate to cleaning of dispense nozzles that dispense epoxy using a chemical treatment, and dispense nozzle cleaners.
Dispense nozzles that dispense epoxy-based materials are used in a variety of semiconductor assembly systems, such as for die attach and die molding systems. In the case of die attach systems, dispense nozzles are commonly used. Partially cured epoxy is known to accumulate on the dispense nozzle holes during use, which results in the need for periodic cleaning of the dispense nozzles to clear blockages for proper dispensing.
The conventional dispense nozzle cleaning process is an exclusively manual operative intensive process. In such a cleaning process, dispense nozzles are soaked in a ultrasonic tank filled with a solvent for softening partially cured epoxy, such as acetone which is known to soften partially cured epoxy. As the dispense nozzles are soaked, the operator picks up the dispense nozzles individually from the solvent solution and uses a wire to pass through the nozzle hole using a back and forth scraping motion to weaken the epoxy bond, which can deform the nozzle tip. The nozzle is then soaked in the solvent which can wash off some of the softened epoxy. A pressurized air or nitrogen gun can also be used to help push the softened epoxy out of the nozzle holes, followed by a rinse in a tank with the epoxy solvent (e.g., acetone) to complete the cleaning process.
The cleaning time for this conventional method is typically about 1 to 2 hours. This conventional cleaning method exposes the operator to solvent fumes as it rapidly evaporates, and moreover epoxy is splattered over the work area. The conventional dispense nozzle cleaning process thus creates a potential health hazard as well as a work area cleanliness problem.
Disclosed embodiments describe dispense nozzle cleaning machines that eliminate or at least reduce clogged and worn-out dispense nozzles due to conventional manual dispense nozzle cleaning that utilizes a wire or similar object for scraping away loosened epoxy. Disclosed embodiments include automated cleaning of dispenser nozzles by directly spraying pressurized epoxy solvents at the dispense nozzles to remove the residual epoxy. A reduced safety risk due to chemical exposure is provided because dispense nozzle cleaning can be performed automatically unlike conventional manual cleaning where the operator is exposed to fumes from the volatile epoxy solvent (e.g., acetone) for hours. Moreover, since disclosed dispense nozzle cleaners are sealed, disclosed embodiments eliminate epoxy splattering over the work area.
One embodiment comprises a dispense nozzle cleaner that includes a cleaning rack having at least one aperture for placement of at least one epoxy dispense nozzle having a nozzle hole and residual epoxy, at least one spray nozzle, and at least one alignment member for aligning the spray nozzle with the epoxy dispense nozzle so that liquid sprayed from the spray nozzle flows through a full length of the epoxy dispense nozzle. A pressure source coupled to a solvent reservoir is for delivering a pressurized cleaning solution including a solvent or solvent mixture for epoxy to an inlet side of the spray nozzle for urging the pressurized cleaning solution through the spray nozzle to be sprayed from its outlet so that the pressurized cleaning solution sprayed flows through the full length of the epoxy dispense nozzle including through the nozzle hole, thereby removing at least a portion of the residual epoxy.
Example embodiments are described with reference to the drawings, wherein like reference numerals are used to designate similar or equivalent elements. Illustrated ordering of acts or events should not be considered as limiting, as some acts or events may occur in different order and/or concurrently with other acts or events. Furthermore, some illustrated acts or events may not be required to implement a methodology in accordance with this disclosure.
Step 102 comprises spraying a pressurized cleaning solution at the epoxy dispense nozzle so that at least a portion of the pressurized cleaning solution that is sprayed flows through a full length of the epoxy dispense nozzle including through the nozzle hole. The cleaning solution comprises a solvent or solvent mixture for epoxy, thereby removing at least a portion of the residual epoxy from the dispense nozzle. Since the residual epoxy is removed solely by action of the pressurized solvent, disclosed methods eliminate or at least reduce clogged and worn-out dispenser nozzles due to conventional manual dispense nozzle cleaning that utilizes a wire or similar object for scraping loosened epoxy. Example solvents for uncured or partially cured epoxy include denatured alcohol, acetone, and toluene, or mixtures thereof.
The spraying can comprise automatically spraying the pressurized cleaning solution for a pre-programmed time. The automatically spraying can comprise using a pressurized gas, such as pressurized air or pressurized nitrogen, to force the transfer of the epoxy solvent from a cleaning solution reservoir storing the epoxy solvent to the epoxy dispense nozzles via spray nozzles that are aligned with the epoxy dispense nozzles so that the epoxy solvent flows through a full length of the epoxy dispense nozzles.
Disclosed methods are generally practiced exclusive of any pump. This aspect helps reduce the fire danger associated with the epoxy solvent.
Step 103 comprises removing the epoxy dispense nozzles from the cleaning rack. Using disclosed methods and cleaners the operator' involvement time during cleaning can be reduced from 1 to 2 hours typical for manual epoxy dispense nozzle cleaning to around 0.2 man-hours due to the automation of the epoxy dispense nozzle cleaning (step 102) provided by disclosed dispense nozzle cleaners. Operators only load epoxy dispense nozzles onto the cleaning rack (step 101) and unload epoxy dispense nozzles from the cleaning rack (103). The operator time saved allows the operator to perform other jobs.
Circulation pipes 116 are for transferring pressurized epoxy solvent 134 from the lower chamber 130 to the upper chamber 110. The solenoid valve 119 shown in
The cleaning time can depend on the time set on the timer. The linear guide 141 ensures that the middle chamber 120 will move in a straight vertical line during its downward or upward movement.
As shown in
A lower chamber 130 provides the cleaning solution reservoir that holds the epoxy solvent 134. In operation of dispense nozzle cleaner 200, pressurized gas forces transfer of the epoxy solvent 134 from the lower chamber 130 to the upper chamber 110 then to the plurality of spray nozzles, then through the epoxy dispense nozzles 122 in the middle chamber 120, and then back to lower chamber 130 by drain fitting 129 coupled to drain valve 138 which is coupled to solvent return tube 139.
As described above, the middle chamber 120 is where the epoxy dispense nozzles having residual epoxy to be cleaned are positioned on the cleaning rack 124. The middle chamber 120 can provide an upper position, which is the cleaning position, and a lower position, which is an epoxy solvent replenishment position. The lower position is where operators can place and remove the epoxy dispense nozzles. It is also a position where the epoxy solvent may be added, such as acetone. The linear guide 141 described above allows the middle chamber 120 to move in a straight vertical line during its downward or upward movement when switching between lower and upper positions.
In operation, the epoxy solvent can be poured into the middle chamber and flows through the drain hose 135 then to the lower chamber 130. Once the lower chamber 130 is filled with epoxy solvent 134, the drain valve 138 can be closed and compressed gas, such as compressed air or nitrogen, can be introduced. As the pressure on the lower chamber increases, it will force the epoxy solvent 134 into the upper chamber 110 through the circulation pipes 116. When the solvent 134 is finished transferring to the upper chamber 110, a compressed gas valve on the lower chamber 130 can close.
Since the upper chamber 110 is now filled with epoxy solvent 134, compressed gas can then be activated to increase the pressure on the upper chamber 110 and push the epoxy solvent 134 to the spray nozzles in the middle chamber 120. The spray nozzles which are aligned to the epoxy dispense nozzles will bombard the epoxy dispense nozzles with the epoxy solvent 134 at high velocity and pressure to push the residual epoxy through the nozzle holes. The sprayed epoxy solvent 134 that passes through the dispense nozzle holes will be returned back to the lower chamber 130 through the drain hose 135.
Example settings include a refilling time of 8 seconds, a cleaning time of 20 seconds, and a process time of 1 hour. The process time can comprise a repetitive cycle of refilling and cleaning steps for the process time, such as 1 hour. The lower chamber pressure and upper chamber pressure while pressurized can be at least 0.2 MPa. As described above, pressurization of the chambers forces flow of epoxy solvent 134 from one chamber to another during the refilling and cleaning cycles.
Although disclosed embodiments are described for cleaning dispense nozzles for a die bonder, disclosed embodiments can be applied to clean other nozzles that dispense epoxy resin. More generally, disclosed embodiments can be integrated into a variety of assembly flows that involve epoxy dispensing though epoxy dispense nozzles to form a variety of different IC devices and related products. Those skilled in the art to which this disclosure relates will appreciate that many other embodiments and variations of embodiments are possible within the scope of the claimed invention, and further additions, deletions, substitutions and modifications may be made to the described embodiments without departing from the scope of this disclosure.
