JP2012015262A - Cleaning method and apparatus of heater tool for thermocompression bonding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method and apparatus of heater tools for thermocompression bonding capable of efficiently removing flux, resin or the like which adheres on the heater tool without mechanically polishing the heater tool, and capable of improving reliability of the bonding by reducing deviation of the bonding without change of thermal distribution on a tip face.SOLUTION: The method includes: a treatment step at the first stage of heating and carbonizing organic contaminations by irradiating an organic contamination adhesion face 12 of a heater tool 10 with carbon dioxide gas laser 20; and a treatment step at the second stage of introducing plasma, which an atmospheric pressure plasma apparatus 30 excites processing gas to inject, onto the adhesion face 12 of the organic contaminations to remove carbonized organic contaminations.

Description

  The present invention relates to a cleaning method and an apparatus for removing flux and resin adhering to a heater tool such as a heater chip for soldering and a heat caulking head for heat caulking of resin parts.

  Conventionally, a pulse heat type soldering apparatus is known. In this method, a heater chip made of a metal (molybdenum, tungsten, stainless steel, invar, etc.) with poor solder wettability is pressed against a work (object to be processed, member to be joined), and a pulse current is applied to the heater chip. Heat is generated by Joule heat and soldering is performed. Here, solder or flux is supplied in advance to the workpiece by plating or coating. For this reason, it is inevitable that the heater chip is contaminated with flux. In addition, the resin adheres to the heat caulking head used for the heat caulking of the resin parts and becomes dirty. Further, in the thermocompression bonding of the resin-coated wire, the resin as the coating material adheres to the crimping head.

  Heater tools such as heater chips, thermal caulking heads, and crimping heads used here are made of metal that is difficult for solder to adhere to. However, if used repeatedly, adhesion of flux and resin is inevitable and repeatedly heated to the joining temperature. Therefore, the flux and resin are firmly fixed. If fixed in this manner, the heat transfer rate to the workpiece decreases (heat transfer decreases), the temperature difference between the heater tool and the workpiece increases, and the workpiece temperature does not reach the set temperature, so that the bondability deteriorates. Sometimes.

  In particular, in a heater head used for heat caulking of resin, a dome-shaped recess is provided on the front end surface, but the resin may remain in the dome (inside the recess). For this reason, not only does the heat transfer decrease and heat caulking becomes insufficient, but the surface shape of the caulking portion does not accurately follow the dome shape, and a clean caulking shape cannot be obtained. Similarly, in the case of the thermocompression bonding of the covered wire, there is a possibility that the resin of the covering material adhered to the heater head is transferred to the thermocompression bonding portion on the workpiece side and the electrical connection becomes incomplete.

JP-A-8-31878 JP-A-10-216931

  In order to prevent such problems, the heater tool is periodically cleaned to remove the adhered flux and resin. For example, cleaning by mechanical contact such as polishing the tip surface of the heater tool (the heating surface that contacts the workpiece) with sand paper or brushing is conceivable. As an example of such a method, Patent Document 1 discloses that a rotating brush is brought into contact with a heating surface of a heater tool to remove carbonized flux from the surface of the heater tool. Patent Document 2 discloses that the tip of a soldering iron is cleaned by air blow.

  In the method of mechanically polishing the tip surface of the heater tool using sand paper or a brush, there is a problem that wear of the tip surface of the heater tool is promoted and the life is shortened. When the tip surface is polished with sandpaper or a brush, the size of the tip surface changes. When a heating current control pattern is set in advance, such as in the pulse heat method, where Joule heat is generated by the current passed through the heater tool and heated, the temperature distribution changes due to the dimensional change of the tip surface, resulting in variations in bonding. This causes the problem of causing Therefore, this mechanical polishing method is not desirable in principle.

  Also, in this method, polishing scraps remain on the front end surface of the heater tool after cleaning, and therefore, it is usually necessary to wipe off with alcohol or the like in order to remove it. Moreover, since the sand paper and the brush side are worn out, it is necessary to periodically replace them. For this reason, the maintenance of the apparatus is troublesome, the operating rate of the apparatus is deteriorated, and the running cost is increased.

  In the method of removing deposits by air blow described in Patent Document 2, it is not possible to remove the hardened and firmly adhered deposits. Deposits are easily deposited on top of each other, and it is almost impossible to remove them by air blow alone. For this reason, it is necessary to use the mechanical polishing together, and in this case, the above problem is unavoidable.

    The present invention has been made in view of such circumstances, and can efficiently remove flux and resin adhering to the heater tool without mechanically polishing the heater tool, and change the temperature distribution on the tip surface. This improves the reliability of the joint by reducing the variation in joining, and when applied to thermal caulking, it can reliably remove deposits adhering to the dome at the tip of the heater tool, and the shape of the thermal caulking can be reduced. In the case of a heater tool for thermocompression bonding of resin-coated wires that can be finished neatly, a heater tool for thermocompression bonding that can reliably remove the adhering resin and improve the bonding reliability. A first object is to provide a cleaning method. It is a second object of the present invention to provide a cleaning device that is directly used for carrying out this method.

According to the present invention, a first object is a cleaning method for removing organic contaminants adhering to a thermocompression heater tool, i) irradiating a carbon dioxide laser on the organic contaminant adhering surface of the heater tool. The first stage treatment process to heat and carbonize the organic contaminants, and ii) the plasma generated by the atmospheric pressure plasma device exciting and emitting the process gas to the adhesion surface of the organic contaminants and carbonized organic contaminants And a second step of removing the heat treatment, and a method for cleaning a heater tool for thermocompression bonding.
Achieved by:

  The second object is a cleaning device for removing organic contaminants adhering to the thermocompression heater tool, a) a carbon dioxide laser device for irradiating the organic contaminant adhering surface of the heater tool with a carbon dioxide laser; B) Atmospheric pressure plasma device that injects plasma excited process gas onto the surface of the organic contaminant on the heater tool, and c) Holds the heater tool and sequentially moves the heater tool from the carbon dioxide laser device to the atmospheric pressure plasma device. A heater tool holding means for moving, and heating and carbonizing organic contaminants with the carbon dioxide laser device, and removing the carbonized organic contaminants with the atmospheric pressure plasma device Achieved by a tool cleaning device.

  According to the first aspect of the present invention, organic contaminants such as flux and resin adhering to the heater tool are selectively heated by carbon dioxide laser irradiation, which is the first stage, and are burned and evaporated. And carbonized further. This is because the carbon dioxide laser used here has a wavelength that is reflected by a heater tool that is a metal and is selectively absorbed by organic contaminants.

  In the next second stage, atmospheric pressure plasma is irradiated to the heating surface (tip surface, processing surface) of the heater tool. The atmospheric pressure plasma apparatus used here is an indirect system in which a gas (process gas) is passed through a plasma generation unit to be converted into plasma and irradiated onto a work (object to be processed, heater tool) for cleaning. In the plasma gas, ions, electrons, radicals, ultraviolet rays, and the like exist, and these remove the dirt on the workpiece by an etching action or an ashing (ashing, burning, peeling) action or the like.

For example, ions (plus ions of gas) collide with the surface of the workpiece, and the carbonized flux or resin residue remaining on the processing surface in the first stage processing is physically blown off from the surface. Also, when organic contaminants such as flux and resin that could not be carbonized in the first stage remain, UV rays are removed by acting on these and causing a chemical reaction (decomposing them into carbon dioxide and water).
According to the second aspect of the present invention, the cleaning device used in this method is obtained.

The conceptual diagram which shows the Example of this invention Process diagram of cleaning process Conceptual diagram of cleaning device Explanatory drawing of thermal caulking head

    The carbon dioxide laser used in the processing step i) has an output of 10 to 30 watts, a wavelength of a wavelength region having a high reflectance to metals and a high absorption rate to organic contaminants, for example, 15 watts and 10.6 μm. (Claim 2). In this case, the laser scans the processing surface to prevent the surface temperature from becoming excessive. For example, the scanning speed is preferably set to 100 mm / sec.

The process gas used in process step ii) can be argon gas (claim 3). The plasma apparatus used here scans repeatedly for about 3 minutes at an output of 150 watts to repel carbonized residues remaining on the processing surface for cleaning.

  5. The cleaning apparatus according to claim 4, wherein the carbon dioxide laser device is provided with a smoke collector / dust collector for collecting / collecting dust near the laser irradiation surface of the heater tool, so that the combustion gas evaporated and carbonized around the laser irradiation surface of the heater tool and fine particles are collected. It is preferable to prevent powder and the like from being scattered around. The smoke collector / dust collector may be provided near the processing surface of the plasma apparatus. The heater tool may be a soldering tool (heater chip) or a resin heat caulking tool (heater head). Or the head for thermocompression bonding of a covered wire may be sufficient.

  In FIG. 1, reference numeral 10 denotes a heater chip as a heater tool, which is used for pulse heat type soldering. The heater chip 10 is obtained by wire-cutting a metal material having a constant thickness, such as W (tungsten), which has high resistance and poor solder wettability. The heater chip 10 has a substantially rectangular frame shape with a cut at the center of the upper side, and the lower side is a horizontal pressing portion (cleaning processing surface) 12. Each of the portions 14 and 14 divided into two at the cut becomes a power supply terminal, and these power supply terminals 14 and 14 are fixed to a pressing head (not shown) with bolts.

  The pressing head moves up and down by a vertically arranged air cylinder, and when the pressing head descends, the pressing portion 12 of the heater chip 10 presses the workpiece with a predetermined set pressure. Here, the work is one in which the lead of the electronic component is held opposite to the circuit pattern of the substrate, and the solder is plated in advance and flux is applied to the joint.

  A heating current, which is a pulse current, is supplied to the power supply terminals 14 and 14 from a power supply circuit (not shown). This current flows to the pressing portion 12 on the lower side, and the heater chip 10 generates heat due to Joule heat. The temperature of the heater chip 10 (the temperature of the pressing portion 12) is detected by a thermocouple, fed back to the temperature control circuit, and the heating current is controlled so as to have a predetermined temperature control profile. When the heater chip 10 reaches a predetermined temperature due to this heating, the solder at the joint is melted (reflowed), and when the solder is solidified by cooling, the pressing head is raised. As a result, soldering is completed.

   When a large number of joints are repeated by the heater chip 10, the flux adheres to the lower surface of the pressing portion 12 of the heater chip 10, that is, the pressing surface. This flux is hardened by the heat of the heater chip 10 and becomes thicker as the number of joining increases and the heating temperature increases. For this reason, the heat transfer from the heater chip 10 to the workpiece is deteriorated (the heat transfer rate is reduced). For this reason, the temperature of the workpiece does not reach the set temperature, and appropriate soldering cannot be performed.

  In the present invention, this fixed flux is removed, and as a first step, the carbon dioxide gas laser selectively heats the flux that is an organic contaminant to carbonize. Then, as a second step, the carbonized contaminant is removed by plasma irradiation.

Reference numeral 20 in FIG. 1 denotes a carbon dioxide laser device. The device 20 is, for example, a commercially available relatively inexpensive carbon dioxide laser marker (for example, CO ₂ laser marker: LP-400 series: model LP-430U of Sunkus Corporation). Can be used. The apparatus 20 can output a laser having an average output of 30 watts (Watt) and a wavelength of 10.6 μm, but is preferably used at 15 watts here. In this case, the laser 22 scans the pressing surface of the heater chip 10 (the lower surface of the pressing portion 12) at a speed of 100 mm / sec so that the laser 22 does not continuously irradiate one place on the pressing surface for a long time. Irradiate evenly.

  By the irradiation of the laser 22, the flux that is a fixed organic substance is selectively heated, burned, and carbonized. A smoke collector / dust collector 24 is installed in the vicinity of the pressing surface of the heater chip 10 to collect / collect smoke (combustion gas, etc.) generated along with the irradiation of the laser 22 and fine carbonized fine powder. At this time, the heater chip 10 made of metal reflects the laser 22 and the laser is scanned, so the heater chip 10 is not overheated and damaged.

  When the first stage processing by the carbon dioxide laser is completed in this way, the heater chip 10 is moved above the atmospheric pressure plasma apparatus 30, and here the second stage processing is performed. The atmospheric pressure plasma apparatus 30 is of an indirect system in which a gas (process gas) such as argon gas is passed through a plasma generation unit to be turned into plasma and irradiated onto the pressing surface of the heater chip 10. For example, it is convenient to have a pen-type plasma head 34 that is separate from the power supply unit 32.

  In this case, a gas supplied from a gas cylinder (not shown) to the power supply unit 32 is sent to the plasma head 34 by the gas pipe 36, and the high frequency power supplied from the power supply unit 32 while passing through the quartz tube serving as the plasma generation unit. Is excited to become plasma and is ejected from the tip of the plasma head 34. Since the plasma head 34 is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2004-172044, 2006-314897, and 2007-323812, the structure thereof will not be described in detail here.

The plasma head 34 is held on a movable table (not shown) that can move horizontally, and can move in parallel with the pressing surface of the heater chip 10. In this case, the plasma output is 150 watts and the scanning is repeated for about 3 minutes to remove the adhered residue. In the plasma gas, ions, electrons, radicals, ultraviolet rays, and the like exist, and these remove the dirt on the workpiece by an etching action or an ashing action (ashing, burning, peeling).

  For example, ions (positive ions of gas) collide with the surface of the workpiece, and the flux and resin carbonized in the first stage treatment are physically blown off from the surface. Also, when organic contaminants such as flux and resin that could not be carbonized in the first stage remain, UV rays are removed by acting on these and causing a chemical reaction (decomposing them into carbon dioxide and water). If the output and time of the plasma used at this time are appropriate, only the deposits can be removed without damaging the heater chip 10. Also in this plasma apparatus 30, it is preferable to provide an exhaust / dust collector 38 for removing gas and fine powder from the vicinity of the processing surface.

  This cleaning method can be carried out, for example, by using a cleaning device 40 shown in FIG. In this figure, reference numeral 42 denotes a conveyance line, which conveys a substrate 46 temporarily fixed with electronic components (IC, surface mount components, etc.) 44 at a predetermined interval. 48 is a circular rotary table. Three sets of soldering heads 50 are attached to the rotary table 48 at equal intervals (120 degree intervals). The heater chip 10 is attached to these heads.

  One head 50 is positioned on the transfer line 42, and at this time, the carbon dioxide laser device 20 is separated by 120 degrees in the rotation direction of the table 48 (clockwise in this embodiment), and the plasma apparatus 30 is further separated by 120 degrees. Each is arranged. In this apparatus 40, soldering is repeated on the workpiece conveyed by the conveyance line 42, and the number of repetitions (the number of treatments) is monitored (step S100 in FIG. 2), and when this number reaches a preset number. The cleaning process is started (step S102).

  First, the table 48 rotates 120 degrees clockwise, and the head 50 having the head 10 to be cleaned is moved to the carbon dioxide laser device 20 (step S104). Here, the processing surface is irradiated with the laser 22 (FIG. 1) to selectively heat organic deposits such as flux adhered to the heater chip 10, to evaporate them, and to carbonize the residue (step S106). . During this process, the head 50 on the transport line 42 performs a bonding process on the workpiece. When the number of times the head 50 is joined during the joining process reaches the set value, the table 48 rotates 120 degrees (step S108).

  The heater chip of the head 50 that has moved from the transfer line 48 is heated and carbonized by the carbon dioxide laser device 20 (step S106), while the head 50 that has finished the treatment of the carbon dioxide laser 20 is transferred to the next plasma device 30. Here, the cleaning is performed by plasma irradiation (step S110). The head 50 that has been cleaned in this way (step S112) enters the transport line 48 by the rotation of the table 48 due to the next cleaning time of the head 50 on the transport line 42, and is used again for the joining process. (Step S114).

  FIG. 4 is a view for explaining a process for joining by resin caulking. In FIG. 6A, reference numeral 60 denotes a thermoplastic resin bonding substrate, and a bonding pin 62 used for bonding by caulking is integrally formed. Reference numeral 64 denotes a plate to be joined to the substrate 60, and a circular joining hole 66 through which the joining pin 62 passes is formed. The to-be-joined plate 64 is overlapped with the joining hole 66 through the joining pin 62 of the joining substrate 60, and at this time, the tip of the joining pin 62 protrudes from the joining hole 66. Reference numeral 68 denotes a metal heater tool for caulking, which is heated by passing an electric current in the same manner as the heater chip 10. A concave portion 70 having a substantially inverted spherical shape is formed on the lower surface (tip surface).

  The joining plate 64 is overlaid on the joining substrate 60 as described above (state (A) in the figure), and in this state, as shown in FIG. When the tool 68 is pressed against the tip of the joining pin 62 and the tip of the joining pin 62 is softened or melted, the tip of the joining pin 62 is molded into the shape of the recess 70 of the heater tool 68. When the resin is cured by cooling the heater tool 68, the tip of the joining pin 62 has a substantially rivet head shape, and the joining substrate 60 and the joined plate 64 are fixed by caulking.

  If the heat caulking joining is repeated many times by the heater tool 68, it is inevitable that the resin adheres to the tip surface or the recess 70. The heater tool 68 is cleaned as described with reference to FIG. That is, first, the tip surface is scanned with a carbon dioxide gas laser, and the attached resin is heated and evaporated or carbonized. Then, it can be cleaned by irradiating plasma together with the process gas to remove the deposits.

10 Heater chip (heater tool)
20 CO2 laser device 22 Laser 24 Smoke collector / dust collector 30 Atmospheric pressure plasma device 38 Smoke collector / dust collector 50 Joining head 60 Joining substrate 62 Joining pin 68 Caulking heater tool

Claims (5)

A cleaning method for removing organic contaminants adhering to a thermocompression heater tool,
i) a first stage treatment process for heating and carbonizing the organic contaminants by irradiating a carbon dioxide laser on the organic contaminant adhesion surface of the heater tool;
ii) a second stage treatment process in which the plasma emitted from the atmospheric pressure plasma apparatus by exciting the process gas is guided to the adhesion surface of the organic contaminants to remove carbonized organic contaminants;
A method for cleaning a heater tool for thermocompression bonding.   The carbon dioxide laser used in the processing step i) has an output of 10 to 30 watts, a wavelength of a wavelength region having a high reflectance to metals and a high absorption rate to organic contaminants, and cleaning the heater tool for thermocompression bonding according to claim 1 Method.   The method for cleaning a heater tool for thermocompression bonding according to claim 1, wherein the process gas used in the process step ii) is an argon gas. A cleaning device for removing organic contaminants attached to a thermocompression heater tool,
a) a carbon dioxide laser device that irradiates a carbon dioxide laser on the organic contaminant-attached surface of the heater tool;
b) an atmospheric pressure plasma device for injecting plasma excited with process gas onto the organic contaminant adhering surface of the heater tool;
c) a heater tool holding means for holding the heater tool and sequentially moving the heater tool from the carbon dioxide laser device to the atmospheric pressure plasma device;
And heating the carbonized organic contaminants with the carbon dioxide laser device, and removing the carbonized organic contaminants with the atmospheric pressure plasma device.   5. The cleaning device for a heater tool for thermocompression bonding according to claim 4, wherein the carbon dioxide laser device is provided with a smoke collector / dust collector for collecting / collecting dust from the vicinity of the laser irradiation surface of the heater tool.

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