Laser-assisted deposition with improved coating

Abstract

To provide a laser-assisted deposition apparatus that is improved in throughput and coating uniformity, and to provide a method for depositing deposition medium on a workpiece.SOLUTION: A laser-assisted deposition apparatus for depositing deposition medium from a tape on a workpiece, comprises a coating section with a deposition material source, first and second regulating members arranged downstream of the deposition material source in spaced relation on either side of the tape such that the distance between the first and second regulating members regulates the thickness of deposition material coated onto the tape in use, and a vibration unit which is operative to agitate the deposition material at the coating section.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a laser-assisted deposition apparatus for depositing a deposition medium onto a workpiece from a tape, and to a method for depositing a deposition medium onto a workpiece from a tape. [Background technology]

[0002] Laser Assisted Deposition (LAD) is a developing technique for depositing deposition materials, especially solder paste, on a workpiece or substrate and can be considered as an alternative to traditional paste deposition techniques such as screen printing. The LAD method is characterized by the use of a flexible tape with paste applied on one side. A laser is directed to irradiate an area on the opposite, i.e. uncoated, side of the tape, which causes a small amount of paste to be ejected from the coated side aligned with the irradiated area. The ejected paste volume can then land on the workpiece at an aligned target location. Compared to traditional screen printing processes, such an approach has two main advantages. First, since the amount of paste ejected from the tape is controlled using a laser, the deposited paste can be controlled more precisely and in smaller amounts than with screen printing, and second, it is more easily possible to deposit additional paste on a previously deposited target, which means that the height of the paste deposition can be precisely controlled.

[0003] A typical LAD apparatus 1 is shown in FIG. 1, shown diagrammatically from the side, for use in depositing a deposition medium, most typically a solder paste 3, from a deposition tape 2 onto a workpiece W, with the Z-axis shown pointing vertically upwards. Typically, the deposition tape 2 is a flexible plastic material, such as, for example, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), or flexible glass, or a composite of two or more such materials, e.g., a layered material. The deposition tape 2 can be stored on a deposition tape storage reel 4 before being coated with the solder paste 3. Before deposition, the deposition tape 2 is threadedly engaged with a used tape reel 5, which is driven in rotation to advance the deposition tape 2, and the drive of the used tape reel 5 causes the deposition tape 2 to be unwound from the deposition tape storage reel 4 and wound onto the used tape reel 5. Various rollers 6 can be used to define the deposition tape path and to provide tension to the deposition tape 2. In particular, two rollers 6A, 6B are used to maintain an area of ​​deposition tape 2 close to and parallel to the top surface of the workpiece W. A laser source 7, including various types of laser sources such as, for example, Nd:YAG laser source, Nd:YLF laser source, Nd:YVO4 laser source, Nd:GdVO4 laser source, Yb:YAG laser source, Er:YAG laser source, Er:Cr:YSGG laser source, Er:YSGG laser source and Gd:WO4 laser source, is positioned above this area and aligned to irradiate a spot on the top surface of deposition tape 2 between the rollers 6A, 6B with a laser beam 8. The bottom surface of deposition tape 2 is coated with solder paste 3 by means of a coating tape 9, which is fed from a coating tape storage reel 10 to a coating tape used reel 11, which can be driven in rotation to advance the coating tape 9. The coating tape 9 may be a flexible plastic material and may advantageously have a similar structure to the deposition tape 2, except that the deposition tape 2 has a hydrophilic surface and the coating tape has a hydrophobic surface.The coating tape 9 and deposition tape 2 are directed into a pasting zone 12 formed between first and second adjustment members in the form of rollers 13, 14, where there is a very small gap between the coating tape and the underside of the deposition tape 2. Solder paste 3 is discharged from a paste dispenser 15 into the pasting zone 12, forming a mass of solder paste 3 between the rollers 13, 14. As the deposition tape 2 and coating tape 9 pass through the pasting zone 12, the hydrophilic underside of the deposition tape 2 becomes coated with solder paste 3, the thickness of the coating being controlled by the distance between the rollers 13, 14, while the hydrophobic surface of the coating tape 9 remains substantially free of paste. It will be appreciated that the terms "hydrophobic" and "hydrophilic" are appropriately applied to water-based fluids rather than flux-based fluids such as solder paste, although in practice solder pastes will exhibit similar wetting properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2023 / 062860 Summary of the Invention [Problem to be solved by the invention]

[0005] However, problems exist with such known apparatus in that the coating process is relatively slow and can produce an uneven paste coating across the surface of the deposition tape 2 .

[0006] The present invention seeks to improve both throughput and coating uniformity. [Means for solving the problem]

[0007] According to the invention, this object is achieved by using vibrational agitation, in particular ultrasonic vibrations, to temporarily reduce the viscosity of a deposition medium such as solder paste during coating. The invention thus exploits the thixotropic nature of the deposition medium to reduce the viscosity of the medium in the coating section of the LAD apparatus.

[0008] According to a first aspect of the present invention, there is provided a laser-assisted deposition apparatus for depositing a deposition medium onto a workpiece from a tape having two major surfaces, the laser-assisted deposition apparatus comprising: a tape advancement mechanism for moving the tape along a travel path through the laser assisted deposition apparatus; a coating section for coating a deposition medium on a first main surface of the tape; a laser source that directs a laser beam onto an illumination region of the second surface of the tape; a workpiece support that supports the workpiece proximate the first surface such that, when the laser beam is directed at the illumination area, a deposition medium located on the first surface and aligned with the illumination area is emitted from the second surface onto the workpiece; It is equipped with The coating section comprises: a deposition material source for applying a deposition material to the first main surface; - first and second adjustment members disposed downstream of the source of deposition material along the path of travel, the first and second adjustment members being spaced apart on either side of the tape such that a distance between the first and second adjustment members adjusts a thickness of deposition material coated on the first major surface of the tape in use; a vibration unit for agitating the deposition material in the coating section; It is equipped with:

[0009] According to a second aspect of the present invention, there is provided a method for depositing a deposition medium onto a workpiece from a tape having two major surfaces, the method comprising the steps of: i) providing a laser assisted deposition apparatus; ii) moving the tape along a travel path through the laser assisted deposition apparatus; iii) coating a deposition medium onto a first major surface of the tape in a coating section of a laser assisted deposition apparatus; iv) directing a laser beam onto a second surface of the tape at the illumination area such that when the laser beam is directed at the illumination area, deposition medium located on the first surface and aligned with the illumination area is emitted from the second surface onto the workpiece; Including, wherein step iii) is a step of applying a deposition material to the first main surface; a step of passing the tape having the deposition material applied on the first main surface between a first adjustment member and a second adjustment member to adjust a thickness of the deposition material coated on the first main surface of the tape; and agitating the deposition material in the coating section.

[0010] Other particular aspects and features of the present invention are set forth in the accompanying claims. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows a schematic side view of a known LAD device. [Diagram 2] FIG. 1 is a schematic side view of a LAD device according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing an enlarged side view of a LAD device according to a second embodiment of the present invention. [Figure 4] FIG. 13 shows a schematic side view of a LAD device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The invention will now be described with reference to the accompanying drawings (not to scale).

[0013] Various embodiments of the present invention will now be described with reference to Figures 2 to 4. In the figures, for simplicity and consistency, like reference numbers have been used to refer to like elements wherever possible.

[0014] A first embodiment of the invention is shown in Figure 2. It shows a LAD apparatus 20 having many similarities to the apparatus 1 shown in Figure 1. However, this apparatus 20 comprises a coating section for coating a first main surface of a tape 2 with a deposition medium such as solder paste 3, which is applied to the first main surface from a deposition material source, here in the form of a paste dispenser 15, and includes first and second vibration units in the form of ultrasonic transducers 21, 22 coupled to respective adjustment members in the form of rollers 13', 14' and embedded therein as shown in Figure 2. The ultrasonic transducers 21, 22 can for example be formed integrally with the respective shafts of the rollers 13', 14'. As with the apparatus 10 of Figure 1, the rollers 13', 14' are arranged downstream of the paste dispenser 15 along the path of movement and are spaced apart on either side of the tape such that the distance between the first and second rollers adjusts the thickness of the solder paste 3 coated on the first main surface of the tape 2 in use. In use, the ultrasonic transducers 21, 22 are switched on during the coating process and the resulting vibrations are transmitted via rollers 13', 14' to the solder paste 3 applied in the coating section. The solder paste 3 has a low viscosity due to its thixotropic properties, aiding the consistency and quality of the coating onto the tape 2.

[0015] In Figure 2, an ultrasonic transducer is used on each of the rollers 13', 14'. In other embodiments, one vibration unit may be provided in association with one of the rollers 13', 14'.

[0016] The embodiment described above with reference to FIG. 2 used a vibration unit including a vibration generator attached to each adjustment member. FIG. 3 shows a schematic side view of a part of an LAD device 30 according to a second embodiment of the invention, in which a vibration unit with a vibration generator is used, which is connected to each adjustment member via a waveguide. In FIG. 3, a vibration generator, here an ultrasonic generator 31, is connected to the roller 14'' via an ultrasonic waveguide, indicated generally at 33. The waveguide 33 may be connected to the shaft 32 of the roller 14'', as shown. The shaft 32 may optionally be hollow. The operation of the device 30 is very similar to that of the device 20 shown in FIG. 2. Although the ultrasonic generator 31 is shown as being connected to only one roller 14'', in other embodiments (not shown) the ultrasonic generator 31 may instead or additionally be connected to the other roller 13''. In this latter case such a link may be provided by two respective ultrasonic waveguides (not shown). Alternatively, there may be a separate vibrating unit (not shown) coupled to the roller 13''.

[0017] FIG. 4 shows a schematic side view of an LAD device 40 according to a further embodiment of the invention. In this embodiment, the coating section comprises first and second adjustment members in the form of a doctor blade 41 located on a tape support surface 42 that is flat at least in the area near the lower edge of the doctor blade 41. The doctor blade 41 is preferably adjustable in the vertical or Z direction as shown so that the required coating thickness of the solder paste 3 can be adjusted, which is determined in all cases by the gap between the tape support surface 42 and the lower edge of the doctor blade 41. A vibration unit in the form of an ultrasonic transducer 43 is attached to the doctor blade 41. When switched on, the ultrasonic transducer 43 transmits ultrasonic vibrations to the doctor blade 41, which in turn transmits the vibrations to the applied solder paste 3, reducing its viscosity and improving the coating.

[0018] In another embodiment, the vibration unit associated with the doctor blade may include a vibration generator, preferably an ultrasonic vibration generator, coupled to the doctor blade 41 via a waveguide, similar to the embodiment shown in FIG.

[0019] Also, in addition to or instead of the vibrating unit associated with the doctor blade 41, other adjustment members may be provided, namely vibrating units associated with the tape bearing surface 42.

[0020] In the laser-assisted deposition apparatus according to the invention, such as in any of the specific embodiments described above, the vibration unit can generate vibrations at a range of frequencies. Ultrasonic vibrations are preferred, with vibrations in the frequency range of about 20 kHz to about 200 kHz being particularly preferred, with a frequency of at least about 30 kHz in one embodiment, and at most about 100 kHz in one embodiment, preferably at most about 80 kHz, more preferably at most about 60 kHz, and even more preferably at most about 50 kHz. However, in practice, the ideal vibration frequency may depend on the type of deposition material used. It is therefore advantageous if the vibration frequency of the vibration unit used is adjustable to accommodate a variety of different deposition media.

[0021] The above described embodiments are merely illustrative and other possibilities and alternatives within the scope of the invention will be apparent to those skilled in the art. [Explanation of symbols]

[0022] 1:LAD device 2: Vapor deposition tape 3: Solder paste 4: Evaporation tape storage reel 5: Used tape reel 6, 6A, 6B: Roller 7: Laser source 8: Laser beam 9: Coating tape 10: Coating tape storage reel 11: Used reel of coating tape 12: Paste application area 13, 13', 13'', 14, 14', 14'', 14': Laura 15: Paste dispenser 20:LAD device 21, 22: Ultrasonic transducer 30:LAD device 31: Ultrasonic generator 32: Axis 33: Ultrasonic Waveguide 40:LAD device 41: Doctor Blade 42: Tape support surface 43: Ultrasonic transducer W: Workpiece

Claims

1. 1. A laser assisted deposition apparatus for depositing a deposition medium onto a workpiece from a tape having two major surfaces, comprising: a tape advancement mechanism for moving the tape along a travel path through the laser assisted deposition apparatus; a coating section for coating a deposition medium on a first main surface of the tape; a laser source for directing a laser beam onto an illumination area on the second surface of the tape; a workpiece support supporting a workpiece proximate to the first surface, the deposition medium being emitted from the second surface onto the workpiece when the laser beam is directed at the illumination area and aligned with the illumination area; It is equipped with The coating section comprises: a deposition material source for applying a deposition material to said first main surface; - first and second adjustment members arranged downstream of the source of deposition material along the path of movement, the first and second adjustment members being spaced apart on either side of the tape such that the distance between the first and second adjustment members adjusts the thickness of deposition material coated on the first major surface of the tape in use; a vibration unit for agitating the deposition material in the coating section; A laser-assisted deposition apparatus comprising:

2. The laser-assisted deposition apparatus of claim 1 , wherein the vibration unit is coupled to the first adjustment member and vibrates the first adjustment member.

3. The laser-assisted deposition apparatus of claim 2 , wherein the vibration unit is a vibration generator attached to the first adjustment member.

4. The laser-assisted deposition apparatus of claim 2 , wherein the vibration unit is a vibration generator connected to the first adjustment member via a waveguide.

5. The laser-assisted deposition apparatus of claim 2 , further comprising a second vibration unit coupled to the second adjustment member for vibrating the second adjustment member.

6. The laser assisted deposition apparatus of claim 1 , wherein the vibration unit is an ultrasonic transducer.

7. 7. The laser assisted deposition apparatus of claim 6, wherein the ultrasonic transducer generates vibrations in a frequency range of 20 kHz to 200 kHz, optionally in a frequency range of at least about 30 kHz, optionally up to about 100 kHz, optionally up to about 80 kHz, optionally up to about 60 kHz, optionally up to about 50 kHz.

8. The laser assisted deposition apparatus of claim 1 , wherein the first adjustment member is a roller.

9. The laser assisted deposition apparatus of claim 8 , wherein the second adjustment member is a roller.

10. The laser assisted deposition apparatus of claim 8 , wherein the second adjustment member comprises a flat tape support surface.

11. 2. The laser assisted deposition apparatus of claim 1, wherein the first conditioning member is a doctor blade and the second conditioning member is a flat tape support surface.

12. 1. A method for depositing a deposition medium onto a workpiece from a tape having two major surfaces, comprising: i) providing a laser assisted deposition apparatus; ii) moving the tape along a travel path through the laser assisted deposition apparatus; iii) coating a deposition medium onto a first major surface of the tape in a coating section of the laser assisted deposition apparatus; iv) directing a laser beam onto a second surface of the tape at the illumination area, whereby deposition medium located on the first surface and aligned with the illumination area is ejected from the second surface onto the workpiece when the laser beam is directed at the illumination area; It is equipped with wherein step iii) is a step of applying a deposition material to the first main surface; a step of passing the tape having the vapor deposition material applied on the first main surface between a first adjustment member and a second adjustment member to adjust a thickness of the vapor deposition material coated on the first main surface of the tape; agitating the deposition material in the coating section; The method comprises:

13. The method of claim 12 , wherein the deposition material is agitated by applying ultrasonic vibrations.

14. 14. The method of claim 13, wherein the ultrasonic vibrations are applied in a frequency range of 20 kHz to 200 kHz, optionally at least about 30 kHz, optionally at most about 100 kHz, optionally at most about 80 kHz, optionally at most about 60 kHz, optionally at most about 50 kHz.

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