Title: Fluid dispense tips
Abstract: A fluid dispense tip includes a bevel at an opening to reduce the amount of surface tension, or "land", at the opening. The bevel is formed by grinding in a longitudinal direction such that any tooling scars resulting from the grinding operation are likewise longitudinally oriented, further reducing the amount of surface tension in the tip, thereby leading to heightened dispensing accuracy. The tip may be machined from stock as a unitary piece, to increase its lifetime, and may be formed with a bore of a relatively large diameter that is tapered down to a smaller diameter near the tip opening, to allow for delivery of fluid through the tip body at a decreased pressure. A cleaning tool may be provided for removing residual material from the inner surfaces of the tip. A removable liner sleeve may be provided within the bore to reduce the effective inner diameter of the dispense tip.
Patent Number: 6,896,202 Issued on 05/24/2005 to Fugere
| Inventors:
|
Fugere; Jeffrey (Sandown, NH)
|
| Assignee:
|
DL Technology, LLC (Haverhill, MA)
|
| Appl. No.:
|
304349 |
| Filed:
|
November 26, 2002 |
| Current U.S. Class: |
239/291; 239/289 |
| Intern'l Class: |
R05B 001/00; A62C031/02 |
| Field of Search: |
29/8884,557,558,890.12
205/652,654,668
239/589,591
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Hwu; Davis
Attorney, Agent or Firm: Mills & Onello LLP
Parent Case Text
RELATED APPLICATIONS
This application is a divisional application of U.S. Ser. No. 09/491,615, filed
Jan. 26, 2000, now U.S. Pat. No. 6,547,167, which claims benefit of provisional
application No. 60/163,938 filed Nov. 8, 1999 and 60/117,201, filed Jan. 26, 1999.
Claims
1. A beveled dispense tip comprising:
an elongated neck having a longitudinal axis, and an elongated hole along the
longitudinal axis, the hole forming an opening at an output end of the neck;
a body about the elongated hole at an input end of the neck, the body having
a larger width than the neck; and
a bevel formed about the opening of the neck by positioning the longitudinal
axis of the neck at an acute angle relative to a direction of travel of a grinding
surface and by rotating the neck about the longitudinal axis, such that tooling
marks on the bevel resulting from the grinding are substantially oriented in a
direction that is coplanar with, and at an acute angle to, the longitudinal axis
of the neck.
2. The beveled dispense tip of claim 1 wherein the bevel is formed by a grinding wheel.
3. The beveled dispense tip of claim 2 wherein grinding occurs along an edge
of the grinding wheel.
4. The beveled dispense tip of claim 2 wherein grinding occurs along a surface
of the grinding wheel.
5. The beveled dispense tip of claim 1 further comprising wherein the beveled
tip is electropolished to substantially buff said longitudinal tooling marks resulting
from grinding.
6. The beveled dispense tip of claim 1 wherein the neck of the dispense tip is
machined from stock.
7. The beveled dispense tip of claim 1 wherein the neck and the body are unitary.
8. The beveled dispense tip of claim 1 wherein the neck and the body are formed
independently and coupled together.
9. The beveled dispense tip of claim 1 wherein the elongated hole includes an
inner taper proximal to the output end of the neck for reducing an inner diameter
of the elongated hole from a first inner diameter of the elongated hole along a
majority of its length to a second inner diameter of the elongated hole along a
minority of its length at the output end.
10. A beveled dispense tip comprising:
an elongated neck having a length along a longitudinal axis and having a width,
the length of the neck being substantially larger than the width of the neck, and
an elongated hole along the longitudinal axis through the neck, the elongated hole
having an opening at an output end of the neck;
a body about the elongated hole at an input end of the neck, the body having
a width that is larger than the width of the neck;
a bevel formed about the opening of the neck by positioning the longitudinal
axis of the neck at an acute angle relative to a direction of travel of a grinding
surface and by rotating the neck about the longitudinal axis; and
tooling marks on the bevel resulting from the grinding; the tooling marks being
substantially oriented in a direction that is coplanar with, and at an acute angle
to, the longitudinal axis of the neck.
11. The beveled dispense tip of claim 10 wherein the bevel is formed by a grinding wheel.
12. The beveled dispense tip of claim 11 wherein grinding occurs along an edge
of the grinding wheel.
13. The beveled dispense tip of claim 11 wherein grinding occurs along a surface
of the grinding wheel.
14. The beveled dispense tip of claim 10 wherein the beveled tip is electropolished
to substantially buff said longitudinal tooling marks resulting from grinding.
15. The beveled dispense tip of claim 10 wherein the neck of the dispense tip
is machined from stock.
16. The beveled dispense tip of claim 10 wherein the neck and the body are unitary.
17. The beveled dispense tip of claim 10 wherein the neck and the body are formed
independently and coupled together.
18. The beveled dispense tip of claim 10 wherein the elongated hole includes
an inner taper proximal to the output end of the neck for reducing an inner diameter
of the elongated hole from a first inner diameter of the elongated hole along a
majority of its length to a second inner diameter of the elongated hole along a
minority of its length at the output end.
19. A beveled dispense tip comprising:
an elongated neck having a longitudinal axis, and an elongated hole along the
longitudinal axis, the elongated hole forming an opening at an output end of the neck;
a body about the elongated hole at an input end of the neck, the body having
a width that is larger than a width of the neck; and
a bevel about the opening of the neck, the bevel being finished by positioning
the longitudinal axis of the neck at an acute angle relative to a direction of
travel of a grinding surface and by rotating the neck about the longitudinal axis,
such that tooling marks on the bevel resulting from the grinding are substantially
oriented in a direction that is coplanar with, and at an acute angle to, the longitudinal
axis of the neck.
20. The beveled dispense tip of claim 19 wherein the grinding is performed on
a grinding wheel.
21. The beveled dispense tip of claim 20 wherein the grinding occurs along an
edge of the grinding wheel.
22. The beveled dispense tip of claim 20 wherein the grinding occurs along a
surface of the grinding wheel.
23. The beveled dispense tip of claim 19 wherein the beveled tip is electropolished
to substantially buff said longitudinal tooling marks resulting from grinding.
24. The beveled dispense tip of claim 19 wherein the neck of the dispense tip
is machined from stock.
25. The beveled dispense tip of claim 19 wherein the neck and the body are unitary.
26. The beveled dispense tip of claim 19 wherein the neck and the body are formed
independently and coupled together.
27. The beveled dispense tip of claim 19 wherein the elongated hole includes
an inner taper proximal to the output end of the neck for reducing an inner diameter
of the elongated hole from a first inner diameter of the elongated hole along a
majority of its length to a second inner diameter of the elongated hole along a
minority of its length at the output end.
28. A beveled dispense tip comprising:
an elongated neck having a length along a longitudinal axis and having a width,
the length of the neck being substantially larger than the width of the neck, and
an elongated hole along the longitudinal axis through the neck, the elongated hole
having an opening at an output end of the neck;
a body about the elongated hole at an input end of the neck, the body having
a width that is larger than the width of the neck;
a bevel about the opening of the neck, the bevel being finished by positioning
the the longitudinal axis of the neck at an acute angle relative to a direction
of travel of a grinding surface and by rotating the neck about the longitudinal
axis; and
tooling marks on the bevel resulting from the grinding; the tooling marks being
substantially oriented in a direction that is coplanar with, and at an acute angle
to, the longitudinal axis of the neck.
29. The beveled dispense tip of claim 28 wherein the grinding is performed on
a grinding wheel.
30. The beveled dispense tip of claim 29 wherein the grinding occurs along an
edge of the grinding wheel.
31. The beveled dispense tip of claim 29 wherein the grinding occurs along a
surface of the grinding wheel.
32. The beveled dispense tip of claim 28 wherein the beveled tip is electropolished
to substantially buff said longitudinal tooling marks resulting from grinding.
33. The beveled dispense tip of claim 28 wherein the neck of the dispense tip
is machined from stock.
34. The beveled dispense tip of claim 28 wherein the neck and the body are unitary.
35. The beveled dispense tip of claim 28 wherein the neck and the body are formed
independently and coupled together.
36. The beveled dispense tip of claim 28 wherein the elongated hole includes
an inner taper proximal to the output end of the neck for reducing an inner diameter
of the elongated hole from a first inner diameter of the elongated hole along a
majority of its length to a second inner diameter of the elongated hole along a
minority of its length at the output end.
Description
BACKGROUND OF THE INVENTION
Contemporary fluid dispense systems are well suited for dispensing precise
amounts of fluid material at precise positions on a substrate. A pump transports
the fluid to a dispense tip, also referred to as a "pin" or "needle", which is
positioned over the substrate by a micropositioner, thereby providing patterns
of fluid on the substrate as needed. As an example application, dispense tips can
be utilized for depositing precise volumes of adhesives, for example, glue, resin,
or paste, during a circuit board assembly process, in the form of dots for high-speed
applications, or in the form of lines for providing underfill or encapsulation.
FIG. 1 is a perspective view of a conventional dispense tip
24. The dispense
tip
24 includes a body
26 and a hollow neck
28. The body
26
attaches to a pump
22, for example by means of a thread, which controls
the amount of fluid to be dispensed. The neck
28 is typically a hollow cylinder
having a first end
31 which is positioned to overlap with an aperture formed
in the body
26, and a second end
30 at which the fluid is dispensed.
As shown in the close-up perspective view of FIG. 2, the neck
28 is formed
by rolling a flat portion of machined metal into a cylindrical form. A seam
40
is welded along the longitudinal axis, to seal the edges of the flat portion, using
conventional seam welding techniques. In precision tips, the inner diameter of
the opening at the second end
30 may be on the order of 0.030 inches in
diameter. The thickness of the walls
32 may be on the order of 0.010 inches.
A hole
29 is bored into the tip body
26, and the neck
28 is
aligned with, and pressed into, the hole. As a consequence of rolling and welding,
the inner diameter of the neck is often unpredictable due to inner collapse.
When fluid is released at the opening
30, a high degree of surface tension
on the substrate is desired, such that the substrate receives and pulls the fluid
from the tip
24. It is further desirable to minimize the surface tension
of the neck
28 interface such that when the pin retracts from the substrate,
dispensed fluid properly remains on the board. However, a certain degree of surface
tension in the neck exists due to the thickness of the walls
32 of the neck
28 at the opening
30.
It has been observed that the surface tension, or "land", at the opening
30
of the neck
28 can be reduced by tapering the outer diameter of the neck
28 to a sharp point. As shown in FIG. 3, the distal end
30 of the
neck
28 is sharpened using a surface grinder
42. The neck
28
is positioned perpendicular to the motion of the grinder
42 as shown, to
thereby generate a taper
36, or bevel, on the distal end of the neck
28.
The tapered portion
36 varies in thickness from the outer diameter of the
neck
28 at position
37A to a sharpened point
37B at the opening
30. For the example given above, by providing a taper
36, the amount
of land at the opening may be reduced from 0.010″ of contact about the perimeter
of the opening, to 0.001″ of contact. In this manner, the surface tension
at the junction of the pin and fluid is highly reduced, leading to a higher degree
of dispensing precision.
As shown in the close-up perspective view of FIG. 4, as a consequence of formation
of the taper
36 in the manner described above, with the neck
28 positioned
substantially perpendicular to the grinding wheel
42, tooling scars, in
the form of radial rings
38, can form on the taper
36 due to surface
variations in the grinding wheel
42. These rings
38 provide ledges
or shelves that can lead to additional surface tension on the taper
36,
which, in turn, capture fluid material when the tip is released from the substrate
following a fluid deposit. This, in turn, can cause fluid to be dispensed inconsistently
on the substrate during subsequent deposits, leading to inaccurate results.
SUMMARY OF THE INVENTION
The present invention is directed to a tapered dispense tip grinding method,
and a dispense tip processed according to such a method, that overcome the aforementioned
limitations associated with conventional techniques. In the present invention,
the tip is presented to the grinding wheel in a longitudinal orientation—the
longitudinal axis of the neck of the tip is substantially aligned with the direction
of movement of the grinding wheel. In this manner, the taper is formed without
the radial rings of conventional techniques, thereby providing a tip with further-reduced
surface tension and therefore increased dispensing precision capability.
In a second aspect, the present invention is directed to an electropolishing
technique
whereby a beveled tip is electropolished to further buff, or remove, tool marks
generated during bevel formation. In this manner, burrs and pits are removed from
the surfaces of the tip. This aspect is applicable to treatment of both conventional
laterally-ground and the inventive longitudinally-ground tapered tips. Electroplating
may further be applied to external and internal tip surfaces to enhance surface lubricity.
In a third aspect, the present invention is directed to a dispense tip formed
in a solid unitary piece, machined from stock. By machining the neck opening, potential
inner collapse of the neck due to rolling as in prior configurations is avoided.
Furthermore, alignment of the neck with the body of the tip is unnecessary and
complicated assembly procedures are thereby avoided. The unitary tips further offer
the advantage of a robust neck, avoiding the need for bonding of the neck to an
alignment foot. Because of the added robustness, the unitary tips are more amenable
to deployment with longer-length necks than conventional configurations.
In a preferred embodiment of the third aspect, the neck is of a first inner diameter
along a majority of its length, and of a second inner diameter proximal to the
opening, the first inner diameter being greater than the second inner diameter.
This configuration allows for delivery of the dispensed fluid to the opening at
a relatively low pressure, as compared to conventional tips having a single, narrow
diameter over their lengths, and is especially attractive to dispensing applications
that require smaller diameter tips.
A preferred embodiment of the third aspect of the present invention comprises
a
unitary fluid dispense tip. The tip includes an elongated cylindrical neck having
a longitudinal axis. A bore is machined in the neck centered at the longitudinal
axis, the bore having an input end and an output end. The input end of the bore
has an inner surface of a first inner diameter and the output end of the bore has
an inner surface of a second inner diameter, the first inner diameter being greater
than the second inner diameter. An inner taper is machined in the bore such that
the inner surface of the bore transitions gradually from the first inner diameter
to the second inner diameter.
The inner taper is preferably proximal to the output end of the neck, and is
preferably formed at an angle of approximately 20–40 degrees relative to
the longitudinal axis of the neck. The neck is preferably formed with a body about
the input end of the neck, the body including a funnel adapted for delivering fluid
to the input end of the neck. The body may optionally be formed separately from
the neck, in which case the body and neck are preferably coupled via press-fitting,
bonding, or welding. An alignment foot may be coupled to the body so as to provide
a vertical gap below the neck during a dispensing operation. Multiple necks may
be mounted to the body, in which case the funnel is adapted for delivering fluid
to the multiple input ends of the multiple necks.
A liner sleeve may be inserted in the neck of the dispense tip in order to reduce
material flow for low-viscosity materials. The sleeve may comprise, for example,
Teflon™ tubing, inserted by a sleeve insertion tool adapted to push the
tubing into the neck, and removed by a sleeve removal tool.
In a fourth aspect, the present invention is directed to a cleaning tool adapted
for cleaning the inner surfaces of the neck of the dispense tip. The cleaning tool
includes an elongated body that serves as a handle during a cleaning operation,
and a sharpened shovel adapted to interface with, and shaped to correspond with,
the tapered inner diameter of the tip neck. The shovel is located on a bevel, the
bevel having an angle substantially similar to the neck taper to allow the shovel
to access the tapered portion of the neck. Optional drill flutes may be formed
on the cleaning tool body for removing a bulk of the material from the inner surface
during a cleaning operation. In this manner, buildup of hardened material is avoided,
and dispense tip lifetime is extended.
In a fifth aspect, the present invention is further directed to a cleaning kit
for cleaning dispense tips configured in accordance with the present invention,
thereby extending the useful lifetime of the dispense tips. The kit is preferably
enclosed in a plastic, non-scratch compartmentalized receptacle, and includes a
pin-vise, magnet, syringe and plunger, magnifying glass, cleaning wires, and cleaning
tools. The pin vise is adapted to secure the miniature wires and drills during
a cleaning operation. The magnet is helpful for locating the wires and drills on
a work surface, for example by using a sweeping motion of the magnet over the surface.
The syringe and plunger are provided for flushing out the dispense tips following
cleaning with the wires and fluted drill bits. Alcohol is a preferred liquid for
the flushing operation. A magnifying glass helps with inspection of the dispense
tips during, and following, cleaning. Cleaning wires include cleaning wires with
tapered ends for eased insertion into the dispense tips. Cleaning tools include
fluted drill bits for coarse cleaning of the inner necks, a shoveled cleaning tool,
described above, for cleaning the inner taper of unitary dispense tips, and a liner
insertion tool, described above, for inserting liners into the unitary dispense tips.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, features and advantages of the invention will
be apparent from the more particular description of preferred embodiments of the
invention, as illustrated in the accompanying drawings in which like reference
characters refer to the same parts throughout the different views. The drawings
are not necessarily to scale, emphasis instead being placed upon illustrating the
principles of the invention.
FIG. 1 is a perspective view of a conventional dispense tip mounted to a dispensing pump.
FIG. 2 is a close-up view of the neck of a conventional dispense tip.
FIG. 3 is a perspective view of lateral grinding of a tip bevel in accordance
with conventional techniques.
FIG. 4 is a perspective view of the radial scars formed on a tip bevel ground
according to conventional lateral grinding techniques.
FIG. 5A and FIG. 5B are side and front views of longitudinal grinding of a tip
bevel in accordance with the present invention.
FIG. 6 is a close-up perspective view of the longitudinal tooling scars resulting
from longitudinal tip grinding in accordance with the present invention.
FIG. 7 is a side view of a tooling fixture for supporting a dispense tip in
proper alignment for longitudinal grinding, in accordance with the present invention.
FIGS. 8A and 8B are side views depicting the dispensing of fluid material on
a substrate in the form of a dot and of a line, respectively.
FIG. 9 is a side view of the dispense tip following dispensing of a dot on a
substrate in accordance with the present invention.
FIG. 10A and FIG. 10B illustrate buffing of a beveled tip according to the electropolishing
technique of the present invention.
FIG. 11A is a cutaway side view of a unitary dispense tip in accordance with
the present invention. FIG. 11B is a close-up cutaway side view of the dispense
tip neck, illustrating a tapered inner diameter near the opening of the neck in
accordance with the present invention.
FIG. 12 is a perspective view of a unitary tip including a spacer foot in accordance
with the present invention.
FIG. 13 is a cutaway side view of a machined neck being applied to a body in
accordance with the present invention.
FIG. 14A is an exploded side view of a dual-neck embodiment including a spacer
foot, in accordance with the present invention. FIG. 14B is a perspective view
of the assembled dispense tip of FIG. 14A, in accordance with the present invention.
FIG. 15A and FIG. 15B are perspective and side views respectively of a tool
for cleaning a dispense tip having a tapered neck in accordance with the present invention.
FIG. 16A and FIG. 16B are side views illustrating cleaning of the tip using
the tool of FIGS. 15A and 15B in accordance with the present invention.
FIG. 17 is a cutaway side view of a unitary tip having a tubular liner inserted
in the neck of the tip in accordance with the present invention.
FIGS. 18A–18D are cutaway side views of the tip of FIG. 17, showing
insertion of the liner with a liner insertion tool in accordance with the present invention.
FIG. 19 is a perspective view of a unitary tip having a reduced diameter in
the region proximal to the tip opening, in accordance with the present invention.
FIG. 20 is a perspective view of a dispense tip cleaning kit in accordance with
the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIGS. 5A and 5B are side and front views respectively depicting longitudinal
grinding of a dispense tip bevel in accordance with the present invention.
In FIG. 5A, a grind wheel rotates in a clockwise direction, for example at a
speed
of 3,200 revolutions per minute (RPM). The neck
28 of the dispense tip is
presented to the grinding wheel such that the longitudinal axis of the neck substantially
aligns with the direction of travel of the grinding wheel. In this manner, a bevel
36 can be formed in a distal end of the neck
28 such that any resulting
tooling scars that arise due to the texture of the grinding wheel are substantially
longitudinally oriented; in other words, substantially parallel to the longitudinal
axis of the dispense tip.
As seen in the close-up diagram of FIG. 6, a bevel
36 is formed on the
dispense tip such that the surface area, or "land" of the tip interface
34
at the opening
32, is substantially reduced. With longitudinal grinding,
longitudinal scars
44 are formed on the tip. All tooling marks are substantially
parallel to the longitudinal axis
45 of the tip neck
28. In this
manner, any fluid dispensed from the tip that brushes up against the surface of
the bevel
36 is more likely to roll off, and therefore be released, from
the tip, as opposed to conventional radial rings, or tooling scars, which tend
to capture and collect droplets of the dispensed material.
FIG. 7 is a side view of an alignment unit
50 for aligning a dispense
tip
24 in proper position for longitudinal grinding at the grinding wheel
42, as described above. The alignment unit includes support
54 for
supporting and positioning the dispense tip
24, and further includes a motor
52, for optionally rotating the dispense tip
24 about its longitudinal
axis
57 in a continuous clockwise or counter-clockwise direction during
grinding, to ensure symmetric bevel formation.
FIGS. 8A and 8B are side views depicting dispensing of fluid material
58
from a dispense tip
28 onto a substrate
56 in the form of a dot
58
in FIG. 8A and in the form of a line
60 in FIG. 8B. Material
58,
60 flowing in the direction of arrow
62 dispensed from the opening
32 of the dispense tip tends to cling to portions of the neck
28
near the opening
32. In FIG. 8A, a dot
58 is formed by positioning
the dispense tip
28 over the substrate
56 at a precise location and
pumping fluid
58 therefrom while the position of the dispense tip
28
and substrate
56 are fixed relative to each other. A fluid line
60
is formed in a similar manner in FIG. 8B by moving either, or both, the dispense
tip
28 and substrate
56 laterally relative to each other, for example
by use of a micropositioner. The distance d between the tip opening
32 and
the upper surface of the substrate
56 is variable depending on the viscosity,
volume, and desired depth of dispensed material, and depending on the geometry
of the dispense tip
28.
As shown in FIG. 8A, dispensed material tends to cling to the side surfaces of
the taper
36 at location
64 near the opening
32 as the tip
is repeatedly positioned to dispense and separate from the dispensed fluid. As
described above, longitudinal grinding of the bevel
36 causes any scars
44 to be parallel to the longitudinal axis of the neck
28 of the
dispense tip and therefore such excess fluid
64 is less likely to cling
thereto, as compared to the radial tooling marks of conventional embodiments.
FIG. 9 is a side view of a dispense tip following dispensing of a dot
58
in accordance with the present invention. As the needle ascends, material
58A
pulls away from the dot
58. This phenomenon is referred to in the industry
as "tailing", and is an adverse result of material that clings
64 and migrates
up the sides of the needle along the taper
36. A problem associated with
this effect is that the following dot dispensed will have an excess amount of material.
As described above, a dispense tip having longitudinal tooling lines
44
according to the present invention helps to minimize this effect.
In a second aspect, the present invention is directed to an electropolishing
technique
for polishing the beveled tip in order to remove scuff or scratch marks resulting
from grinding. This aspect is applicable to treatment of both conventional laterally-ground
and the inventive longitudinally-ground tapered dispense tips. To that end, the
beveled portion of a dispense tip having radial scars
38A or longitudinal
scars
44A as shown in FIG. 10A is immersed in an electropolishing bath to
enhance the finish of the tip and to quickly bring the tooled portions of the tip
to a high luster and smooth finish. This results in a dispense tip having minimal
radial scars
38B or longitudinal scars
44B as shown in FIG. 10B.
This process further removes microscopic burrs that corrupt dispense flow and further
functions as a final clean-up process for the dispense tips. Electropolishing units
of the types applicable to the present invention are commercially available from
a number of vendors, including ESMA, Inc. of South Holland, Ill. To effect electropolishing,
electrodes are first attached to the dispense tip, and the tip and electrodes are
submerged in a chemical solution, for example an acid bath. The electrodes are
activated for a time period, for example two seconds, and are removed, and neutralized,
for example by flushing in water.
The present invention is further directed, in a third aspect, to a solid, machined,
unitary dispense tip as shown in FIG. 11A. The unitary tip
84 includes a
body
70 and a neck
72. The tip
84 is preferably machined from
oversized stock by a lathe, the stock being of a diameter slightly larger than
the desired body
70 diameter. In a high-production environment, the stock
may be presented to the machining lathe by an automated stock feeder.
In an exemplary procedure for forming the unitary tip
84, the body
70
is held in the spindle of a lathe and a bulk portion of stock is removed about
the neck
72. Next, a bore of diameter D
2 equal to the desired
diameter of the opening
74 (see FIG. 11B) is formed concentric with the
longitudinal center axis of the neck
72. The neck
72 and body
70
are next buffed and finished, and the body
70 is separated or cut from the
stock. The rear face
71 of the body
70 is finished, and a neck bore
78 is formed through the body
70 and neck
78, the bore being
concentric with the opening
74 and being of a diameter D
1, slightly
larger than the diameter D
2 of the opening
74.
As shown in the close-up side view of FIG. 11B, the neck bore
78 stops
short of the opening
74. At the interface of the neck bore
78 and
opening
74, a taper
80 is formed to gradually conform the two diameters
D
1, D
2. The taper
80 is preferably finished with a
finishing drill to provide a smooth inner surface, as well as a predetermined taper
angle α for the inner neck, for example 20–40 degrees. A funnel
76
is formed and finished in the body
70 at a taper angle β, for example
45 degrees. Other taper angles are equally applicable to the present invention,
depending on the application. A bevel
36 is optionally formed near the opening
74, and is preferably longitudinally ground in accordance with the aforementioned
techniques to provide the various advantages described above. While the above description
illustrates formation of the inner taper
80 proximal to the opening
74,
the invention is equally applicable to tips formed with an inner taper
80
toward the middle, or body end
70, of the neck
72.
An important feature of this aspect of the invention is the ability to deliver
fluid to an opening
74 of a relatively narrow inner diameter D
2
at relatively low pressure as compared to conventional tips (for example the rolled
tip of FIG. 2) having the single narrow inner diameter D
2 over the length
of the neck. The wider diameter D
1 along the length of the neck
72
allows for delivery of the fluid to the narrow diameter D
2 opening
74
at a relatively low pressure. This is especially helpful for small-gauge tips and
allows for quicker dispensing, while lowering pressure requirements on the pump
delivering the fluid.
In an alternative embodiment, as shown in the perspective view of FIG. 12, a
vertical
alignment foot
82 is optionally disposed in a bore
86 formed in the
body
70. The foot
82 is adapted for reliable and accurate vertical
positioning of the tip opening
74 over the substrate during dispensing of
the material. The foot
82 may be formed of a number of materials, including
heat-treated steel optimized for wear resistance, as well as plastic, investment
casting, injection mold, stainless steel, or titanium, and may be press-fit, bonded,
or welded into the body
70. The foot
82 may optionally be formed
to include a radiused end
83, to allow for contact with the substrate without
damaging the substrate, for example for applying a line of material to the substrate,
as described above with reference to FIG. 8B.
FIG. 13 is a cutaway side view of a dispense tip
84 formed by the combination
of a separately machined neck
72 joined to body
70. The neck
72
is machined in the manner described above and preferably includes the advantageous
configuration of a tapered inner diameter as described above. A bore
88
is formed in the body and the neck
72 is press-fit, bonded, or welded into
position in the bore
88.
FIG. 14A is an exploded perspective view of a dual-dispense tip embodiment,
including first and second tips
72A,
72B machined separately as described
above, and joined to a body
70 having first and second apertures
88A,
88B communicating with a dual output funnel
76. An alignment foot
82 is likewise aligned with, and disposed in, bore
89. The resulting
dual-dispense tip is shown in perspective in FIG. 14B. Once aligned, the necks
72A,
72B may be bonded to the foot
82 using epoxy
90
to ensure rigidity and alignment throughout the lifetime of the dispense tip. Alternative
embodiments including, for example, three or four dispense tips are equally applicable
to the present invention.
To extend dispense tip lifetime, the present invention is further directed, in
a fourth aspect, to a cleaning tool
93 as shown in the perspective and side
views respectively of FIG. 15A and FIG. 15B. The cleaning tool
93 includes
an elongated body
94 that serves as a handle during a cleaning operation,
and a sharpened surface, referred to herein as a "shovel"
100, adapted to
interface with the tapered inner diameter of the neck
72, as described above.
The body
94 of the cleaning tool is preferably of a diameter slightly less
than the diameter of the larger first diameter D
1 of the neck, while
the angle of the bevel
98 is adapted to match the angle α of the inner
taper
80 of the neck. Drill flutes
102 may be provided on the body
94 of the cleaning tool
94, for providing an initial cleaning of
the contaminated region, and for transporting a bulk of the material from the neck region.
A cleaning operation using the cleaning tool
93 is illustrated in the
side
view of FIG. 16A and FIG. 16B. As shown in FIG. 16A, material residue
92
is deposited on an inner surface of the neck
72. The end of the cleaning
tool
93 having drill flutes is inserted and rotated in the neck for removing
a bulk of the residual material from the inner surface of the neck. The cleaning
tool
93 is next inserted in the rear portion of the dispense tip at funnel
76. As shown in FIG. 16B, the cleaning tool
93 is inserted and rotated
so as to remove the material
92 from the inner surfaces of the neck. The
cleaning tool
94 is beveled at its distal end
98 such that the tip
interfaces with the tapered portion, as shown. The sharpened shovel
100
scrapes residue from the tapered portion of the neck. As shown in FIG. 16B, the
residual material is substantially removed from the inner surface by the cleaning
tool
93.
In another aspect of the present invention, the dispense tip
84 includes
a tubular sleeve or insert
120 positioned within the neck, as shown in the
cutaway side view of FIG. 17. The tubular insert may comprise, for example a Teflon™
tube liner
120 cut in length to match the length of the neck of the dispense
tip between the inner taper
80, and the funnel
76.
As explained above, the unitary machined dispense tips of FIGS. 11–14
with
a tapered inner diameter offer the advantages of increased material flow, and operation
at lower pressure, resulting in improved dispensing accuracy and increased throughput.
However, as the viscosity of the material for deposit is lowered, the material
tends to flow through the neck more quickly, such that if the inner diameter of
the neck is too large, the resulting deposit may be too wide in diameter. The tubular
neck insert
120 serves to narrow the neck width such that a given machined
dispense tip can be made to be compatible with a variety of materials, including
low-viscosity materials, simply by applying a sleeve of appropriate inner diameter.
The lined embodiment is beneficial for forming dispense tips having inner diameters
too small to machine. The effective inner diameter of the dispense tip is thus
defined by the inner diameter of the liner, which can be easily adjusted by removing
and inserting different liners. This embodiment confers the additional advantage
of simplified tip cleaning, as the liner can be readily removed and discarded.
The liner
120 may be inserted, for example, using an insertion tool
130
according to the process illustrated in FIGS. 18A–18D. The liner insertion
tool
130 may comprise, for example, an elongated wire
134, of a diameter
smaller than the inner diameter of the insert
120. The wire is passed through
a soft casing
135 comprising, for example, rubber or plastic, that serves
jointly as a handle for the insertion tool, and as a stop to urge the liner into
the tip during insertion. As shown in FIG. 18A, one end of the tool is inserted
entirely through the hole in the liner
120, thereby ensuring the liner is
not blocked. In FIG. 18B, the liner is pushed into the neck opening in the funnel
of the dispense tip
84. During insertion, an end of the handle
135
urges the liner into the neck opening
78, as shown in FIG. 18C. The taper
80 at the distal end of the neck
78, near its opening
74,
prevents further insertion of the tube
120 into the neck, and serves to
retain the liner
120 in the neck
78 as the insertion tool
130
is withdrawn, as shown in FIG. 18D. The lined dispense tip
84 is now ready
for operation. The liner may be removed by twisting a fluted drill bit of appropriate
diameter into the end of the liner at funnel
76, so as to cut into the inner
walls of the liner. The liner
120 is then withdrawn form the neck with the
drill bit.
FIG. 19 is a perspective view of a unitary dispense tip having a reduced outer
diameter OD2 in the region proximal to the tip opening, referred to herein as a
"relieved" dispense tip. The relieved tip is formed with a neck
72 of standard
first outer diameter OD1. The relieved region of the neck
72B proximal to
the neck opening
74 is machined further to a narrower second outer diameter
OD2. The reduced second outer diameter allows for the dispense tip to be positioned
closer to the side of an object on the substrate, for example for underfill or
encapsulation of integrated circuits or "flip chips". The longitudinal length
of the relieved neck region
72B is a function of the thickness of the object
being encapsulated.
In another aspect of the present invention, a cleaning kit as shown in FIG. 20
further enables cleaning of the dispense tips. Such a kit is preferably enclosed
in a plastic, non-scratch compartmentalized receptacle
150, and includes
a pin-vise
152, magnet
154, syringe
156 and plunger
158,
magnifying glass
160, cleaning wires
162 and cleaning tools
164.
The pin vise
152 is adapted to secure the miniature wires and drills during
a cleaning operation. The magnet
154 is helpful for locating the wires and
drills on a work surface, for example by using a sweeping motion of the magnet
over the surface. The syringe and plunger
156,
158 are provided for
flushing out the dispense tips following cleaning with the wires and fluted drill
bits. Alcohol is a preferred liquid for the flushing operation. A magnifying glass
160 helps with inspection of the dispense tips during, and following, cleaning.
Cleaning wires
162 include cleaning wires with tapered ends for eased insertion
into the dispense tips. Cleaning tools
164 include fluted drill bits for
coarse cleaning of the inner necks, a shoveled cleaning tool, described above,
for cleaning the inner taper of unitary dispense tips, and a liner insertion tool,
described above, for inserting liners into the unitary dispense tips.
Commonly dispensed materials include solder paste, conductive epoxy, surface
mount epoxy, solder mask, two-part epoxy (for encapsulation), two-part epoxy underfill,
oils, flux, silicone, gasket materials, glues, and medical reagents. The dispense
tips may be formed of a number of applicable materials, including stainless steel,
ceramics, composites, glass, and molded epoxy.
While this invention has been particularly shown and described with references
to preferred embodiments thereof, it will be understood by those skilled in the
art that various changes in form and detail may be made therein without departing
from the spirit and scope of the invention as defined by the appended claims.
*
