Laser assisted deposition with improved coating

Abstract

A laser assisted deposition apparatus for depositing a deposition medium from a tape onto a workpiece, comprising: a coating portion having a source of deposition material; a first adjustment member and a second adjustment member disposed downstream of the deposition material source in spaced apart relationship on either side of the tape such that a distance between the first adjustment member and the second adjustment member in use adjusts a thickness of the deposition material applied to the tape; and a vibration unit operable to agitate the deposition material at the coating portion.

Description

Technical Field

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

[0002] Laser assisted deposition (LAD) is a developing technology for depositing deposition materials, particularly solder paste, onto a workpiece or substrate and can be considered an alternative to traditional solder paste deposition techniques such as screen printing. The LAD process is characterized by the use of a flexible tape with solder paste applied on one side. The laser is directed to illuminate an area on the opposite side of the tape (i.e. the uncoated side), which causes a small amount of solder paste to be ejected from the coated side aligned with the illuminated area. The ejected volume of solder paste can then land on the workpiece aligned to the target location. This method has two main advantages over the traditional screen printing process: firstly, since the amount of solder paste ejected from the tape is controlled by the use of a laser, the deposited solder paste can be more accurately controlled and the amount of solder paste deposited is less compared to screen printing; secondly, it is easier to deposit additional solder paste onto a previously deposited target, which means that the height of the solder paste deposit can be precisely controlled.

[0003] exist Figure 1, a typical LAD device 1 is schematically shown from the side, for depositing a deposition medium (most typically solder paste 3) from a deposition belt 2 onto a workpiece W, with the Z axis shown pointing vertically upward. Typically, the deposition belt 2 is a flexible plastic material, such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI) or flexible glass, or a composite material of more than one of the above materials, such as a layered material. Before applying the solder paste 3, the deposition belt 2 can be stored on a deposition belt storage reel 4. Before deposition, the deposition belt 2 is threaded onto a used belt reel 5, which is rotatably driven to advance the deposition belt 2, so that the drive of the used belt reel 5 causes the deposition belt 2 to unwind from the deposition belt storage reel 4 and wind around the used belt reel 5. Various rollers 6 can be used to define the deposition belt path and provide tension to the deposition belt 2. In particular, two rollers 6A, 6B are used to keep an area of ​​the deposition belt 2 close to and parallel to the upper surface of the workpiece W. The laser source 7 may include various types of laser sources, such as 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, and is positioned above the region aligned so as to irradiate a point on the upper surface of the deposition tape 2 between the rollers 6A, 6B with the laser beam 8. The solder paste 3 is applied to the lower side of the deposition tape 2 by using a coating tape 9, which is fed from a coating tape storage reel 10 to a coating tape use reel 11, which is rotatably driven to advance the coating tape 9. The coating tape 9 may include 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 belt 9 and the deposition belt 2 are transferred to a solder paste application zone 12 formed between a first regulating member and a second regulating member in the form of rollers 13, 14, where a very small gap exists between the coating belt and the underside of the deposition belt 2. Solder paste 3 is released from a solder paste dispenser 15 into the solder paste application zone 12, thereby forming a large amount of solder paste 3 between the rollers 13, 14. As the deposition belt 2 and the coating belt 9 move through the solder paste application zone 12, the hydrophilic underside of the deposition belt 2 is 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 belt 9 remains substantially free of solder paste. It should be understood that the terms "hydrophobic" and "hydrophilic" are strictly applicable to water-based fluids, rather than flux-based fluids such as solder paste, but in practice solder paste exhibits similar wetting characteristics.

[0004] However, a problem with this known device is that the coating process is relatively slow and also results in an uneven coating of solder paste over the entire surface of the deposition strip 4 .

[0005] The present invention aims to improve the production yield and coating uniformity.

[0006] According to the present invention, this object is achieved by using vibration agitation, in particular ultrasonic vibration, to temporarily reduce the viscosity of the deposition medium such as solder paste during coating. Therefore, the present invention utilizes the thixotropy of the deposition medium to reduce the viscosity of the medium of the coating part of the LAD device. Summary of the invention

[0007] According to a first aspect of the invention, there is provided a laser assisted deposition apparatus for depositing a deposition medium from a belt onto a workpiece, the belt having two main surfaces, the laser assisted deposition apparatus comprising:

[0008] a tape advancement mechanism for moving the tape along a travel path through the laser assisted deposition apparatus,

[0009] a coating section for coating the first main surface of the belt with a deposition medium,

[0010] a laser source operable to direct a laser beam onto the second surface of the belt at the illumination area, and

[0011] a workpiece support for supporting the workpiece proximate the first surface so that when the laser beam is directed to the illumination area, the deposition medium located on the first surface aligned with the illumination area is discharged from the second surface onto the workpiece,

[0012] The coating part includes:

[0013] a deposition material source for applying a deposition material to the first major surface,

[0014] first and second regulating members arranged along the travel path downstream of a source of deposition material and in spaced relationship on either side of the belt such that a distance between the first and second regulating members regulates, in use, a thickness of deposition material applied to the first major surface of the belt, and

[0015] A vibration unit operable to agitate the deposited material at the coating portion.

[0016] According to a second aspect of the invention, there is provided a method of depositing a deposition medium from a belt onto a workpiece, the belt having two major surfaces, the method comprising the steps of:

[0017] i) provide laser assisted deposition equipment,

[0018] ii) moving the strip along a moving path through a laser assisted deposition device,

[0019] iii) coating the first major surface of the tape with a deposition medium in a coating section of a laser assisted deposition apparatus, and

[0020] iv) directing a laser beam onto a second surface of the belt at the illumination area such that when the laser beam is directed to the illumination area, deposition medium located on the first surface of the belt aligned with the illumination area is expelled from the second surface onto the workpiece,

[0021] Wherein step iii) comprises: applying a deposition material to the first main surface,

[0022] passing the belt having the deposition material applied to the first major surface between the first conditioning member and the second conditioning member to adjust the thickness of the deposition material applied to the first major surface of the belt, and

[0023] The deposited material is stirred in the coating section.

[0024] Further particular aspects and features of the invention are set out in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will now be described with reference to the accompanying drawings (not to scale), in which:

[0026] Figure 1 A known LAD device is schematically shown from the side;

[0027] Figure 2 A LAD device according to a first embodiment of the present invention is schematically shown from the side;

[0028] Figure 3 schematically shows an enlarged side view of a LAD device according to a second embodiment of the present invention; and

[0029] Figure 4 A LAD device according to a third embodiment of the present invention is schematically shown from the side.

[0030] Description of reference numerals:

[0031] 1-LAD equipment

[0032] 2- Sedimentary belt

[0033] 3-Solder paste

[0034] 4-Deposition tape storage reel

[0035] 5- Used tape reel

[0036] 6, 6A, 6B - Roller

[0037] 7-Laser source

[0038] 8-Laser beam

[0039] 9-Coating tape

[0040] 10-Coating tape storage reel

[0041] 11-Reel for coating tape

[0042] 12-Solder paste application area

[0043] 13, 13', 13", 14, 14', 14", 14"' - Roller

[0044] 15-Solder Paste Dispenser

[0045] 20-LAD equipment

[0046] 21, 22-Ultrasonic transducer

[0047] 30-LAD equipment

[0048] 31-Ultrasonic generator

[0049] 32-axis

[0050] 33-Ultrasonic Catheter

[0051] 40-LAD equipment

[0052] 41-Scraper

[0053] 42-with support surface

[0054] 43-Ultrasonic transducer

[0055] W-workpiece. DETAILED DESCRIPTION

[0056] Now refer to Figures 2 to 4 Various embodiments of the present invention are described. In these drawings, for simplicity and consistency, the reference numerals of similar components will be kept consistent as much as possible.

[0057] Figure 2 The first embodiment of the present invention is shown in FIG. The figure shows a LAD device 20, which is connected to Figure 1 The apparatus 10 shown has many similarities. However, the apparatus 20 comprises an application section for applying a deposition medium, such as solder paste 3, to the first main surface of the strip 2, the solder paste 3 being applied to the first main surface from a deposition material source, here in the form of a solder paste dispenser 15, comprising a first and a second vibration unit in the form of ultrasonic transducers 21, 22 connected to respective adjustment members in the form of rollers 13', 14', and as shown Figure 2 The ultrasonic transducers 21, 22 may be formed integrally with the respective shafts of the rollers 13', 14', for example. Figure 1Like the device 10 of the present invention, the rollers 13', 14' are arranged downstream of the solder paste dispenser 15 along the moving path and are spaced apart on either side of the belt, so that the distance between the first roller and the second roller adjusts the thickness of the solder paste 3 applied to the first main surface of the belt 2 in use. In use, the ultrasonic transducers 21, 22 are turned on while the coating process is in progress, and the vibrations generated are transmitted to the solder paste 3 applied in the coating section via the rollers 13', 14'. Due to its thixotropic properties, the solder paste 3 becomes less viscous, which helps to improve the consistency and quality of the coating on the belt 2.

[0058] exist Figure 2 In the embodiment, an ultrasonic transducer is used in each roller 13', 14'. In other embodiments, a single vibration unit may be provided, associated with a single one of the rollers 13', 14'.

[0059] Reference above Figure 2 The described embodiments use a vibration unit including a vibration generator mounted to a corresponding adjustment member. Figure 3 A part of a LAD device 30 according to a second embodiment of the present invention is schematically shown in an enlarged side view, wherein a vibration unit including a vibration generator is used, which is connected to a corresponding adjustment member via a waveguide. Figure 3 In the embodiment of the present invention, a vibration generator (here an ultrasonic generator 31) is connected to the roller 14" via an ultrasonic waveguide schematically shown as 33. As shown, the waveguide 33 can be connected to the shaft 32 of the roller 14". Optionally, the shaft 32 can be hollow. The operation of the device 30 is very similar to Figure 2 Operation of the device 20 shown. Although the ultrasonic generator 31 is shown connected to only one roller 14", in other embodiments (not shown) it may alternatively or additionally be connected to another roller 13". In the latter case, such connection may be provided by two corresponding ultrasonic ducts (not shown). Optionally, a separate vibration unit (not shown) may be provided that is connected to the roller 13".

[0060] Figure 4A LAD device 40 according to another embodiment of the present invention is schematically shown from the side. In this embodiment, the coating section includes a first adjustment member and a second adjustment member in the form of a scraper 41 located above a belt support surface 42, which is flat at least in the area close to the lower edge of the scraper 41. As shown in the figure, preferably, the scraper 41 is adjustable in the vertical or Z direction to allow the desired coating thickness of the solder paste 3 to be adjusted, which thickness is in any case determined by the gap between the belt support surface 42 and the lower edge of the scraper 41. The scraper 41 has a vibration unit in the form of an ultrasonic transducer 43 mounted thereon. When turned on, the ultrasonic transducer 43 transmits ultrasonic vibrations to the scraper 41, which in turn transmits vibrations to the applied solder paste 3, reducing its viscosity to improve the coating.

[0061] In an alternative embodiment, the vibration unit associated with the scraper may include a vibration generator, preferably an ultrasonic vibration generator, which is connected to the scraper 41 via a waveguide, similar to Figure 3 The embodiment shown.

[0062] Furthermore, in addition to or as an alternative to the vibration unit associated with the scraper 41 , a vibration unit associated with the other conditioning member, ie the belt support surface 42 , may be provided.

[0063] In the laser assisted deposition apparatus according to the present invention, for example in any of the above-mentioned specific embodiments, the vibration unit can generate vibrations within a certain frequency range. Ultrasonic vibration is preferred, and the vibration is particularly preferably within a frequency range of about 20 kHz to about 200 kHz, in one embodiment, at a frequency of at least about 30 kHz, in one embodiment, at a frequency of up to about 100 kHz, preferably up to about 80 kHz, more preferably up to about 60 kHz, and even more preferably up to about 50 kHz. However, in practice, the ideal vibration frequency may depend on the type of deposition material used. Therefore, it is advantageous if the vibration frequency of the vibration unit used is adjustable to accommodate a variety of different deposition media.

[0064] The above-described embodiments are merely exemplary, and other possibilities and alternatives within the scope of the present invention will be apparent to those skilled in the art.

Claims

1. A laser-assisted deposition apparatus for depositing a deposition medium from a belt onto a workpiece, the belt 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 the first main surface of the belt with a deposition medium, a laser source operable to direct a laser beam onto the second surface of the tape at the illumination area, and a workpiece support for supporting a workpiece proximate to the first surface so that when the laser beam is directed to the illumination area, the deposition medium located on the first surface aligned with the illumination area is discharged from the second surface onto the workpiece, Wherein, the coating part comprises: a deposition material source for applying deposition material to the first major surface, a first regulating member and a second regulating member arranged downstream of the source of deposition material along the travel path and in spaced relationship on either side of the belt such that the distance between the first regulating member and the second regulating member regulates, in use, the thickness of the deposition material applied to the first major surface of the belt, and A vibration unit is operable to agitate the deposition material at the coating portion.

2. The laser-assisted deposition apparatus according to claim 1, wherein: The vibration unit is connected to the first adjusting member to achieve vibration of the first adjusting member.

3. The laser-assisted deposition apparatus according to claim 2, wherein: The vibration unit includes a vibration generator mounted to the first adjusting member.

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

5. The laser-assisted deposition apparatus according to claim 2, comprising: A second vibration unit is connected to the second adjusting member to achieve vibration of the second adjusting member.

6. The laser-assisted deposition apparatus according to claim 1, wherein: The vibration unit includes an ultrasonic transducer.

7. The laser-assisted deposition apparatus according to claim 6, wherein: The ultrasonic transducer generates vibrations 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.

8. The laser-assisted deposition apparatus according to claim 1, wherein: The first regulating member includes a roller.

9. The laser-assisted deposition apparatus according to claim 8, wherein: The second regulating member includes a roller.

10. The laser-assisted deposition apparatus according to claim 8, wherein: The second adjustment member includes a planar belt supporting surface.

11. The laser-assisted deposition apparatus according to claim 1, wherein: The first conditioning member includes a scraper and the second conditioning member includes a flat belt supporting surface.

12. A method for depositing a deposition medium from a belt onto a workpiece, the belt having two major surfaces, the method comprising the steps of: i) provide laser assisted deposition equipment, ii) moving the strip along a travel path through the laser assisted deposition apparatus, iii) coating the first major surface of the tape with a deposition medium in a coating section of the laser assisted deposition apparatus, and iv) directing a laser beam onto a second surface of the belt at an illumination area such that when the laser beam is directed to the illumination area, the deposition medium located on the first surface aligned with the illumination area is expelled from the second surface onto the workpiece, in, Step iii) comprises: applying the deposition material to the first major surface, passing the belt having the deposition material applied to the first major surface between a first conditioning member and a second conditioning member to adjust the thickness of the deposition material applied to the first major surface of the belt, and The deposition material is stirred in the coating portion.

13. The method according to claim 12, wherein: The deposited material is agitated by applying ultrasonic vibration.

14. The method according to claim 13, wherein: The ultrasonic vibrations are applied at a frequency in the 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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