Adhesive dispensing unit

Abstract

The present disclosure relates to an adhesive dispensing unit for a semiconductor die bonding apparatus, the adhesive dispensing unit comprising: an adhesive dispensing nozzle; and a pin member; the pin member includes a lower strut portion and a sheath portion, and wherein the lower strut portion is reciprocally movable within the sheath portion.

Description

[0001] This application is a divisional application of the patent application with the application number 2020114056737, the application date of December 2, 2020, and the invention title of "Adhesive Dispensing Unit". Technical Field

[0002] The present disclosure relates to an adhesive dispensing unit for a semiconductor die bonding device. In particular, the present disclosure relates to an adhesive dispensing unit for dispensing a viscous die attach material (die attach adhesive). Background Art

[0003] In semiconductor devices, leadframes are metal support structures on which semiconductor dies (chips) are mounted. The leadframe is used to connect the terminals of the semiconductor die to external leads that transmit electrical signals from the die. Leadframes are typically made of copper sheets or copper sheet alloys and typically have a thickness in the range of 100 μm to 300 μm. Semiconductor dies are typically attached to the leadframe by a conductive adhesive material.

[0004] Due to the ductility of the leadframe metal, leadframes often warp or bend before use, and this can cause problems in that it is difficult to hold the leadframe by vacuum on a work holder such as a shuttle or a dispensing plate due to vacuum leakage. A typical representation of a bent or warped leadframe 102 mounted on a work holder 104 is shown as Figure 1 shown. Depending on the thickness of the leadframe material and other manufacturing factors (such as stamping, etching, and / or bending, etc.), the amount of leadframe warping varies between different leadframes.

[0005] This clamping difficulty and the variation in the amount of leadframe warping can cause problems when positioning the leadframe on the work holder 104 and may thus impede the precise dispensing of the conductive adhesive material 108 on the leadframe 102. The position error caused by the fact that the spacing X between the adhesive dispensing head 106 and the leadframe 102 may vary and be uncertain according to the amount of leadframe warping is shown in Figure 1 .

[0006] The adhesive material 108 forms droplets at the opening of the adhesive dispensing head 106. The adhesive droplets at the opening of the adhesive dispensing head 106 can be formed by capillary action or by a pump (such as an Archimedes screw pump, where a single screw rotates in a cylindrical cavity), so as to move the adhesive material 108 along the axis of the spiral shaft to the opening of the adhesive dispensing head 106.

[0007] The amount of adhesive dispensed can vary as the spacing X increases or decreases. A smaller spacing X will squeeze the droplet between the tip of the needle and the lead frame, making the droplet larger in size. Larger droplets may also cause contamination of the sidewalls of the dispensing head.

[0008] Figures 2a to 2d An arrangement for attempting to minimize position error is shown, where the adhesive dispensing head 106 includes a fixed lower strut member 110. In Figure 2a this, a droplet is formed at the opening of the adhesive dispensing head 106, and the lower strut 110 fixed to the adhesive dispensing head 106 approaches the lead frame 102. In Figure 2b this, the lower strut 110 contacts the lead frame 102, and depending on the amount of warpage of the lead frame, the droplet of the adhesive material 108 may also contact the lead frame at this time. In Figure 2c this, the movement of the lower strut 110 finally forces the lead frame 102 to contact the workpiece holder 104, so that the warpage on the lead frame is flattened by the lower strut 110. Ideally, at this stage, the droplet of the adhesive material 108 will contact the lead frame for the first time, rather than earlier as described above, depending on the amount of warpage of the lead frame 102. In Figure 2d this, the lower strut rises from the lead frame 102. Initially, the lead frame will no longer be flattened against the workpiece holder 104, and the lead frame will warp upward. When the adhesive dispensing head 106 moves away from the lead frame 102, the adhesive material will remain on the lead frame 102.

[0009] The problem with the above type of arrangement is that the contact time between the droplet of the adhesive material 108 and the lead frame 102 depends on the degree of warpage of the lead frame 102, and as explained, the degree of warpage of the lead frame may vary between different lead frames. For precise and repeatable droplet volume control, the time when the droplet of the adhesive material 108 contacts the lead frame 102 should be known.

[0010] Therefore, the die attach process is affected by the above position error, which is caused by the uncontrolled dispensing of the viscous die attach material. This position error will limit the minimum size of the package, which affects the amount of adhesive dispensed on the lead frame, and to overcome this position error, additional space is required to prevent the adhesive from contaminating the nearby areas. In addition, the position error may slow down the bonding process and die attach in the die bonder, which typically operates at a throughput of 10,000 to 100,000 units per hour (uph), and any slowdown may result in a throughput reduction of 25% to 75%.

[0011] There are alternative solutions where window clips are arranged around a series of die pads on a lead frame, such that the window clips hold the lead frame around them. When the window clips are fixed, the adhesive dispensing head moves over the window and the adhesive is dispensed appropriately. Then the window clips are released and moved to the next series of die pads. However, this arrangement limits the speed at which the adhesive dispensing head can operate due to the need to move the dispensing head over the window. Summary of the Invention

[0012] Various exemplary embodiments address problems such as those mentioned above and / or other problems that may become apparent from the following disclosure of improvements.

[0013] In certain exemplary embodiments, aspects of the present disclosure relate to:

[0014] According to an embodiment, there is provided an adhesive dispensing unit for a semiconductor die bonding apparatus, the adhesive dispensing unit including: an adhesive dispensing nozzle; and a pin member; the pin member includes a lower strut portion and a sheath portion, and wherein the lower strut portion is capable of reciprocating within the sheath portion.

[0015] The lower strut portion can be biased within the sheath portion by an elastic biasing member.

[0016] The elastic biasing member can be a spring member.

[0017] The pin member can be mountably arranged adjacent to the adhesive dispensing nozzle.

[0018] The maximum extension of the pin member relative to the adhesive dispensing nozzle can be in the range of 0.3 mm to 10 mm.

[0019] The adhesive dispensing unit according to an embodiment further includes a housing, wherein the adhesive dispensing nozzle and the pin member are mounted to the housing.

[0020] The housing can include a pump mechanism configured and arranged to pump an adhesive material to the adhesive dispensing nozzle. The pump mechanism can be an Archimedes screw. Brief Description of the Drawings

[0021] To enable a detailed understanding of the features of the present disclosure, a more specific description is provided with reference to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only show typical embodiments and should not be considered as limiting its scope. The drawings are provided for ease of understanding the present disclosure and are not necessarily drawn to scale. After reading this specification in conjunction with the drawings, the advantages of the claimed subject matter will become apparent to those skilled in the art. In the drawings, the same reference numerals are used to denote the same elements, and wherein:

[0022] Figure 1 Shows an existing adhesive dispensing head before dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder;

[0023] Figure 2a Shows an existing adhesive dispensing head with a lower strut member before dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder;

[0024] Figure 2b Shows an existing adhesive dispensing head with a lower strut member during dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder;

[0025] Figure 2c Shows an existing adhesive dispensing head with a lower strut member during dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder;

[0026] Figure 2d Shows an existing adhesive dispensing head with a lower strut member after dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder;

[0027] Figure 3a Shows an adhesive dispensing unit according to an embodiment;

[0028] Figure 3b Shows according to Figure 3a a cross-sectional view of the adhesive dispensing unit;

[0029] Figure 4a Shows an adhesive dispensing unit according to an embodiment before dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder;

[0030] Figure 4b Shows an adhesive dispensing unit according to an embodiment before dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder; and

[0031] Figure 4c Shows an adhesive dispensing unit according to an embodiment during dispensing the conductive adhesive material and a lead frame mounted on a workpiece holder. Detailed Description

[0032] Figure 3a Shows an adhesive dispensing unit 300 for a semiconductor die bonding apparatus according to an embodiment. The adhesive dispensing unit 300 includes a housing 301, an adhesive dispensing nozzle such as a dispensing needle 302 mounted on the housing 301, and a pin member 306 mounted on the housing 301. Generally, the dispensing needle 302, the pin member 306, and the housing 301 are formed of a metal such as steel, copper, aluminum, or a metal alloy.

[0033] The housing 301 includes a first input portion 318 for inputting an adhesive into the housing. The housing 301 contains a pump mechanism (not shown) such as an Archimedes screw, which receives the pressurized adhesive via the first input portion 318, and the first input portion supplies the pressurized adhesive. Those skilled in the art will understand that any suitable pump mechanism can be used. The spindle 316 of the pump mechanism can be arranged at the first end of the chamber 314, and the dispensing needle 302 is arranged at the second end of the chamber 314 away from the first end.

[0034] Figure 3b An internal cross-sectional view of an adhesive dispensing unit for a semiconductor die bonding apparatus is shown, and more particularly, the dispensing needle 302 and the pin member 306 according to Figure 3a are shown.

[0035] The dispensing needle 302 includes a passage 303 therethrough to allow a liquid die attach adhesive to be dispensed from a container (not shown) through the first input portion 318 via the pump mechanism in the chamber 314 and dispensed to the passage 303 of the dispensing needle 302. The liquid adhesive is pumped from the container under pressure and dispensed by the dispensing needle 302 under the pressure of the pump mechanism, whereby the liquid adhesive is dispensed through the passage 303 of the dispensing needle 302 to a target location, such as the surface of a substrate (e.g., a lead frame), etc. The dispensing needle 302 is arranged adjacent to and side by side with the pin member 306 at the second end of the chamber. Ideally, the dispensing needle 302 should be as close as possible to the pin member without contacting the pin member 306.

[0036] The pin member 306 includes a lower strut 310 and a sheath member 308, and the lower strut member 310 is reciprocally movable within the sheath member 308 between a first position and a second position. Generally, the difference between the maximum and minimum ranges of the pin member is 2 mm. However, those skilled in the art will understand that this can be any suitable value depending on the predicted deformation of the lead frame.

[0037] The sheath member 308 can be a separate component connected to the housing 301 of the dispensing unit 300, or alternatively, the sheath member 308 can be a simple passage formed in the housing 301 to allow the lower strut member 310 to reciprocate within the sheath member 308. The lower strut member 310 can be elastically biased within the sheath member 308 such that the lower strut member 310 extends outwardly from the sheath member 308, and by applying a force greater than the elastic biasing force, the lower strut member 310 can reciprocate within the sheath member 308. The elastic biasing can be achieved by a biasing spring such as a helical spring or a cantilever spring. However, although this embodiment contemplates a helical spring or a cantilever spring, those skilled in the art will understand that any suitable elastic biasing device can be utilized. Generally, the lower strut member and the pin member are formed of a metal such as stainless steel, ss steel, or gold-plated brass, etc.

[0038] Reference will now be made to Figures 4a to 4c describe the operation of the dispensing unit 300 according to an embodiment. For clarity and ease of understanding, the dispensing unit 300 and the workpiece holder are shown in a simplified block form, and Figures 4a to 4c the same reference numerals in Figure 3a and Figure 3b represent the same features as in

[0039] As Figure 4a shown, the workpiece holder 404 holds the lead frame 402 in place. The workpiece holder 404 can be a vacuum-type suction cup workpiece holder that includes a flat upper surface on which the lead frame is firmly held by applying a vacuum pressure. Vacuum-type suction cup workpiece holders are commonly used for non-ferrous material lead frames. Alternatively, in the case where the lead frame is a ferrous material, a magnetic type of suction cup can be used. Regardless of the type of workpiece holder, the lead frame 402 may warp or distort when it is located on the workpiece holder, for example Figure 4a as shown by the upward bending of the lead frame 402 in

[0040] Droplets of the liquid adhesive are formed at the opening of the dispensing needle 302 by a pump mechanism in the chamber 314. When the dispensing needle 302 of the dispensing unit 300 approaches the lead frame, since the lead frame is fixed to the workpiece holder 404, the lower strut 310 of the pin member 306 contacts the lead frame. As Figure 4b shown, when the downward force of the pin member 306 elastically biased in the sheath member 308 is greater than the upward force of the warped lead frame, the lower strut 310 will push the lead frame towards the top surface of the workpiece holder such that the lead frame is pushed to be substantially flat on the top surface of the workpiece holder. As Figure 4cAs shown, due to the elastically biased lower strut 310 that can reciprocate within the sheath member 308, the dispensing needle 302 can continue to move towards the lead frame such that the lower strut 310 can move within the sheath member 308 until a droplet of the liquid die attach adhesive contacts the lead frame. Contact between the lead frame and the liquid die attach adhesive causes the die attach adhesive to be dispensed onto the lead frame by capillary action.

[0041] As Figure 4c shown, the gap between the dispensing needle 302 and the opening is controlled by determining the height of the workpiece holder before dispensing and by the defined position of the lead frame on the workpiece holder.

[0042] In this way, the lower strut 310 of the dispensing unit 300 ensures that the lead frame is substantially flat, as any warping or deformation that causes the lead frame to be positioned above the workpiece holder is eliminated by forcing the lead frame to conform to the surface of the workpiece holder. Additionally, the above arrangement ensures that any amount of warping or deformation up to 10 mm in the lead frame can be eliminated.

[0043] Furthermore, the reciprocating motion characteristics of the lower strut 310 allow the distance between the dispensing needle 302 and the lead frame to be controlled, thereby controlling the shape of the die attach adhesive. Thus, due to the constant moving distance of the dispensing needle 302, the time for a droplet of the liquid die attach adhesive to attach to both the needle 302 and the lead frame is reduced, thereby improving the repeatability of the adhesive dispensing as described above.

[0044] Based on the foregoing disclosure, those skilled in the art will thus recognize that the dispensing unit 300 allows for improved dispensing of the die adhesive. Additionally, since the pin member 306 acts in-line, i.e., it acts as the dispensing needle 302 dispenses the die attach adhesive, the dispensing unit according to the embodiment will not slow down the die adhesive dispensing process when compared to conventional dispensing units. Due to the improved volume control, the yield will increase, the package can be smaller, the pitch can be smaller, and thus the speed is increased. The improved volume control of the adhesive dispensing will also result in less time for cleaning the dispensing needle, thereby enabling the adhesive dispensing unit to have more uptime.

[0045] The specific and preferred aspects of the invention are set forth in the appended independent claims. Combinations of features of the dependent and / or independent claims may be appropriately combined, not just as set forth in the claims.

[0046] The scope of the present disclosure includes any novel feature or combination of features that are explicitly or implicitly disclosed, or any generalization thereof, regardless of whether they relate to the claimed invention or mitigate any or all of the problems solved by the invention. The applicant hereby draws attention to the fact that during the examination of this application or any such further application derived therefrom, new claims may be filed with respect to these features. In particular, with reference to the appended claims, features from dependent claims may be combined with features of independent claims, and features from individual independent claims may be combined in any suitable manner, not only in the specific combinations recited in the claims.

[0047] Features described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, for the sake of brevity, the various features described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

[0048] The term "comprising" does not exclude other elements or steps, and the articles "a" or "an" do not exclude a plurality. The reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. An adhesive dispensing unit for a semiconductor die bonding device, The adhesive dispensing unit includes: An adhesive dispensing nozzle; And a pin member, the pin member includes a lower strut portion and a sheath portion, and Wherein, the lower strut portion can reciprocate within the sheath portion.

2. The adhesive dispensing unit according to claim 1, wherein, The lower strut portion is biased within the sheath portion by an elastic biasing member.

3. The adhesive dispensing unit according to claim 2, wherein, The elastic biasing member is a spring member.

4. The adhesive dispensing unit according to claim 1, wherein, The pin member is mounted to be arranged adjacent to the adhesive dispensing nozzle.

5. The adhesive dispensing unit according to claim 2, wherein, The pin member is mounted to be arranged adjacent to the adhesive dispensing nozzle.

6. The adhesive dispensing unit according to claim 3, wherein, The pin member is mounted to be arranged adjacent to the adhesive dispensing nozzle.

7. The adhesive dispensing unit according to claim 1, wherein, The maximum extension of the pin member relative to the adhesive dispensing nozzle is in the range of 0.3 mm to 10 mm.

8. The adhesive dispensing unit according to claim 2, wherein, The maximum extension of the pin member relative to the adhesive dispensing nozzle is in the range of 0.3 mm to 10 mm.

9. The adhesive dispensing unit according to claim 3, wherein, The maximum extension of the pin member relative to the adhesive dispensing nozzle is in the range of 0.3 mm to 10 mm.

10. The adhesive dispensing unit according to claim 4, wherein, The maximum extension of the pin member relative to the adhesive dispensing nozzle is in the range of 0.3 mm to 10 mm.

11. The adhesive dispensing unit according to claim 1 further includes a housing, wherein, The adhesive dispensing nozzle and the pin member are mounted on the housing.

12. The adhesive dispensing unit according to claim 2 further includes a housing, wherein, The adhesive dispensing nozzle and the pin member are mounted on the housing.

13. The adhesive dispensing unit according to claim 3 further includes a housing, wherein, The adhesive dispensing nozzle and the pin member are mounted on the housing.

14. The adhesive dispensing unit according to claim 4 further includes a housing, wherein, The adhesive dispensing nozzle and the pin member are mounted on the housing.

15. The adhesive dispensing unit according to claim 7 further includes a housing, wherein, The adhesive dispensing nozzle and the pin member are mounted on the housing.

16. The adhesive dispensing unit according to claim 11, wherein, The housing includes a pump mechanism configured and arranged to pump an adhesive material to the adhesive dispensing nozzle.

17. The adhesive dispensing unit according to claim 16, wherein, The pump mechanism is an Archimedes screw.

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