JPWO2010018679A1 - Method for manufacturing printed wiring board on which surface mount components are mounted - Google Patents

Abstract

The method for manufacturing a printed wiring board is a method for manufacturing a printed wiring board (107) on which surface-mounted components (100) are mounted. The surface mount component includes a plurality of electrodes (100a, 100b). The printed wiring board includes a plurality of lands (103, 103a, 103b). The plurality of lands are provided corresponding to the plurality of electrodes. Each land is soldered to a corresponding electrode. The manufacturing method includes a step of applying solder (104a, 104b) on a printed wiring board, a step of applying a surface mount component on the printed wiring board after applying the solder, and between an electrode and a land due to the surface tension of molten solder. Identifying an inferior electrode whose adhesion is weaker than the adhesion between other electrodes and lands, and causing the light beam to melt the solder on the identified inferior electrode faster than the solder of the other dominant electrode. Irradiating. This prevents the inferior electrode from coming off the land.

Description

  The present invention relates to a method of manufacturing a printed wiring board on which surface-mounted components are mounted, and more specifically, a printed wiring board is obtained by soldering a surface-mounted component onto a printed wiring board coated with solder using a light beam. It relates to a method of manufacturing.

  With the increasing functionality of mobile phones, game machines, music devices, cameras, etc., ultra-high density surface mounting technology is required. More specifically, the adoption of thin substrate mounting, flexible printed circuit (FPC) mounting, 0402 (0.4 mm × 0.2 mm) component mounting, and POP (Package On Package) mounting has begun to be considered. .

  Factors affecting quality in surface mounting include (1) board and design, (2) metal mask, (3) solder printing, (4) solder paste, (5) electronic components, (6) component mounting, (7 ) There is quality such as reflow.

  In normal process design, in consideration of component variations, solder printing accuracy, and component mounting accuracy, misalignment of components is prevented from occurring. However, since the surface-mounted components are very small, soldering defects called “component standing” and “component displacement” are likely to occur in the reflow process. When a difference in surface tension of molten solder occurs between both electrodes of a surface-mounted component, the surface of the component stands by lifting one electrode from one land and soldering only the other electrode to the other land. This is a phenomenon in which a mounted component stands, and is generally called a Manhattan phenomenon or a Tombstone phenomenon. In the following, one electrode that is detached from the land due to the standing of the part is referred to as a “dominant electrode”, and the other electrode is referred to as a “dominant electrode”. The component shift is a phenomenon in which the position of the surface mount component is shifted with respect to the land position. Both standing of parts and displacement of parts cause connection failure in which the electrodes come off the land, leading to a decrease in manufacturing yield. Hereinafter, component standing and component displacement are collectively referred to as “component standing etc.”.

  Japanese Patent Laying-Open No. 2003-69203 discloses a method for calculating an allowable amount of a mounting position of a surface mounting component. In this method, an accurate mounting position tolerance is calculated based on a moment that suppresses the occurrence of the Manhattan phenomenon and a moment that promotes the occurrence of the Manhattan phenomenon. However, this publication does not disclose any specific reflow method for preventing the Manhattan phenomenon.

  In view of the above problems, the present invention provides a method for manufacturing a printed wiring board on which a surface-mounted component that prevents an electrode from being detached from a land is mounted.

  The manufacturing method according to the present invention is a method for manufacturing a printed wiring board on which surface-mounted components are mounted. The surface mount component includes a plurality of electrodes. The printed wiring board includes a plurality of lands. The plurality of lands are provided corresponding to the plurality of electrodes. Each land is soldered to a corresponding electrode. The manufacturing method includes the steps of applying solder on the printed wiring board, applying the solder and then mounting the surface mount component on the printed wiring board, and the adhesion between the electrode and the land due to the surface tension of the molten solder. A step of identifying an electrode (inferior electrode) weaker than the adhesion force between the electrode and the land, and a light beam so as to melt the solder on the identified inferior electrode side faster than the solder of the other electrode (dominant electrode) Irradiating.

  According to the present invention, since the solder on the inferior electrode side is melted quickly, the adhesive force of the inferior electrode is quickly increased. As a result, the inferior electrode can be prevented from coming off the land.

  The “solder” in the present invention is, for example, lead-containing solder containing lead and tin as main components, solder containing silver, gold-based solder, and lead-free containing tin, silver and copper, tin and bismuth or the like as main components. Includes solder. “Solder” may include, for example, an additive such as flux to prevent oxidation and facilitate connection. “Solder” may include, for example, solder paste and solder cream.

  Other features, elements, steps, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the invention with reference to the accompanying drawings.

It is a functional block diagram which shows the whole structure of the manufacturing apparatus of the printed wiring board by which the surface mounting components by preferable embodiment of this invention were mounted. It is a top view which shows the structure of the soldering apparatus in FIG. FIG. 3 is a schematic diagram showing a configuration of the laser head in FIG. 2 and its periphery. It is a schematic diagram which shows the other example of the laser head shown in FIG. It is a flowchart which shows operation | movement of the manufacturing apparatus shown in FIG. FIG. 4 is a side view for explaining the cause of component standing in the surface-mounted component shown in FIG. 3. FIG. 4 is a side view of a surface-mounted component and a printed wiring board that do not easily stand up because the positions of electrodes of the surface-mounted component placed on the printed wiring board are not shifted. FIG. 4 is a side view of a surface-mounted component and a printed wiring board that are liable to stand up because the positions of the electrodes of the surface-mounted component placed on the printed wiring board are shifted. It is a perspective view which shows the method of irradiating a single laser beam to the electrode of surface mounting components in order using the soldering apparatus shown in FIG. FIG. 5 is a perspective view showing a method of irradiating two laser beams with different intensities or timings on the electrodes of the surface-mounted component using the soldering apparatus shown in FIG. 4. FIG. 5 is a side view of a surface-mounted component and a printed wiring board that do not easily stand up because the position of solder printed on a land is not shifted. FIG. 4 is a side view of a surface-mounted component and a printed wiring board that are liable to stand up because the position of solder printed on a land is shifted. Surface-mounted components and printed wiring that are prone to component standing because the position of the electrodes of the surface-mounted components placed on the printed wiring board is shifted to the right and the position of the solder printed on the land is shifted to the right. It is a side view of a board. Surface-mounted components and printed wiring that are prone to stand-up because the position of the electrodes on the surface-mounted components placed on the printed wiring board is shifted to the left and the position of the solder printed on the land is shifted to the right It is a side view of a board. Since both the position of the electrode of the surface mounting component placed on the printed wiring board and the position of the solder printed on the land are not shifted, it is a plan view of the surface mounting component and the printed wiring board in which the component does not easily shift. is there. Although the position of the solder printed on the land is not deviated, the position of the electrode of the surface mount component placed on the printed wiring board is deviated. is there. Since both the position of the electrode of the surface mount component mounted on the printed wiring board and the position of the solder printed on the land are shifted in the same direction, the surface mount component and the printed wiring board that are liable to be displaced. It is a top view. Since both the position of the electrode of the surface mounting component mounted on the printed wiring board and the position of the solder printed on the land are shifted in different directions, the surface mounting component and the printed wiring board that are liable to cause the component shifting. FIG. It is a top view of the printed wiring board which has a land for grounding. It is the top view which formed the solder resist on the printed wiring board shown to FIG. 13A. It is the top view which printed the solder paste on the printed wiring board shown to FIG. 13B. It is the top view which mounted surface mount components on the printed wiring board shown to FIG. 13C. It is a top view which shows the spreading | diffusion of a heat | fever when soldering the surface mount component shown to FIG. 13D with a laser beam. It is a graph which shows the time change of the temperature of the normal land in FIG. 14, and the time change of a laser output. It is a graph which shows the time change of the temperature of the land for grounding in FIG. 14, and the time change of a laser output.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  [Overall configuration of manufacturing equipment]

  FIG. 1 is a functional block diagram showing the overall configuration of a printed wiring board manufacturing apparatus on which surface-mounted components according to a preferred embodiment of the present invention are mounted. With reference to FIG. 1, the manufacturing apparatus 1 includes a host computer 10, a solder printer 20, a solder inspection machine 30, surface mounters (chip mounters) 40 </ b> A and 40 </ b> B, and a soldering apparatus 50. The manufacturing apparatus 1 is an apparatus that manufactures a printed wiring board on which surface-mounted components are mounted by mounting surface-mounted components on the printed wiring board.

  A host computer 10 that controls each device connected by a HUB (hub) includes a controller 10a, a memory 10b, a display 10c, and an input device 10d. A control command is sent from the application on the host computer 10 to each device. The printed wiring board on which the surface mount component is mounted is sent in the board conveyance direction indicated by the arrow in the figure.

  First, the solder printer 20 prints cream solder on a printed wiring board. The solder inspection machine 30 inspects the position of the printed solder. The inspection result is sent to the surface mounters 40A and 40B and the soldering apparatus 50 via the host computer 10. The surface mounters 40A and 40B mount surface mount components on a printed wiring board. A plurality of surface mounters 40A and 40B are used side by side to improve work efficiency. Not only two surface mounters but also three or more surface mounters may be provided.

  Thereafter, the printed wiring board is conveyed to the soldering apparatus 50. The soldering apparatus 50 locally irradiates the solder on the printed wiring board with a laser beam, thereby heating and melting the solder and soldering the surface-mounted component to the printed wiring board.

  The surface mounters 40A and 40 mount minute surface mount components represented by 0402 components. Even if the printing position is shifted in the solder printing process or the surface mounting component is shifted in the component mounting process, if the deviation is within a predetermined range, the soldering apparatus 50 can detect the deviation by an appropriate laser irradiation method. Irradiate with a laser beam so that becomes small.

  [Soldering equipment]

  FIG. 2 is a plan view showing an external configuration of the soldering apparatus 50. Referring to FIG. 2, the soldering device 50 includes a printed wiring board transport device 251, a laser head 200, and an XYZ robot 271. The soldering apparatus 50 solders the surface-mounted component 100 to the printed wiring board 107 with a laser beam.

  The printed wiring board transport device 251 transports the input printed wiring board 107 to a predetermined position. A surface mount component 100 is mounted on the printed wiring board 107.

  The laser head 200 irradiates the electrode of the surface mount component 100 and the land of the printed wiring board 107 with a laser beam. The XYZ robot 271 conveys the laser head 200 in the X and Y directions and the Z direction (perpendicular to the X and Y directions) in the drawing.

  [Laser head]

  FIG. 3 shows the configuration of the laser head 200 and its periphery. With reference to FIG. 3, the soldering apparatus 50 further includes a semiconductor laser 303, an optical fiber cable 305, an image processing apparatus 325, and a controller 327.

  The laser head 200 includes a collimator lens 307, a half mirror 309, a condenser lens 321, a coaxial camera 323, galvano mirrors 311, 313, a telecentric lens 315, lens driving devices 317a and 317b, a positioning camera 301, including. Therefore, when the laser head 200 is moved by the XYZ robot 271, all the components included in the laser head 200 are also moved together.

  The semiconductor laser 303 is a light source that generates a laser beam. The generated laser beam is guided to the collimator lens 307 through the optical fiber cable 305. The collimator lens 307 collimates the laser beam. The half mirror 309 transmits the laser beam from the collimator lens 307 straight, and reflects the laser beam reflected and returned from the surface mount component 100 and the printed wiring board 107 almost at right angles.

  The galvanometer mirrors 311 and 313 scan the electrodes 100a and 100b of the surface mount component 100 and the land 103 of the printed wiring board 107 with a laser beam by swinging the laser beam transmitted through the half mirror 309 at high speed. The telecentric lens 315 directs the laser beam from the galvanometer mirrors 311 and 313 almost directly below. The lens driving devices 317a and 317b focus the telecentric lens 315 by driving the telecentric lens 315 in the optical axis direction. The positioning camera 301 images the fiducial mark (recognition mark) of the printed wiring board 107 and detects the position and direction of the surface mount component 100.

  [Other examples of laser heads]

  FIG. 4 is a schematic diagram showing a configuration of a laser head 202 used in place of the laser head 200. The laser irradiation device 467a corresponds to the galvanometer mirrors 311 and 313 and the telecentric lens 315 shown in FIG. 3, and outputs the laser beam reflected by the half mirror 309. The laser head 202 further includes an exhaust device 357 for exhausting molten solder paste and flux mist.

  The soldering device 50 further includes another laser irradiation device 467b. The laser irradiation device 467b has the same configuration as the laser irradiation device 467a. Thereby, both the electrodes 100a and 100b of the surface mount component 100 can be soldered simultaneously by two laser beams. Three or more laser irradiation apparatuses may be provided.

  [Operation of solder printer and soldering device]

  Hereinafter, the operations of the solder printer 20 and the soldering apparatus 50 will be described with reference to the flowchart of FIG.

  The solder printer 20 prints a solder paste (including flux) on the printed wiring board 107 (S101). The solder inspection machine 30 measures the position of the printed solder, the displacement of the printing position, and the amount of solder (solder height) (S103). The solder inspection machine 30 sends the inspection result to the soldering apparatus 50 (S105).

  On the other hand, in the soldering apparatus 50, the controller 327 controls the printed wiring board transport device 251 so as to transport the loaded printed wiring board 107 to a predetermined position (S201).

  The positioning camera 301 reads the fiducial mark on the printed wiring board 107 (S203), and recognizes the positions of the printed wiring board 107 and the surface mounting component 100 (S205).

  The positioning camera 301 images the surface-mounted component 100 on the printed wiring board (S207). The controller 327 recognizes the mounting state of the surface mounting component 100 and the positional deviation from the land 103 based on the image photographed by the positioning camera 301 and processed by the image processing device 325 (S209). Based on the inspection result of the solder inspection machine 30 and the recognized positional deviation, the controller 327 specifies a component that is likely to stand up, and determines a laser irradiation method suitable for the component (S211). That is, the controller 327 accepts information for identifying an inferior electrode having an adhesion force between the electrodes of the surface-mounted component 100 and the land of the printed wiring board 107 that is weaker than the adhesion force between other electrodes and lands due to the surface tension of the molten solder. . The controller 327 also determines the laser irradiation method so that the solder on the inferior electrode side specified by the received information is melted earlier than the solder on the other dominant electrode side.

  The controller 327 selects the surface mount component 100 in the order programmed in advance, and controls the XYZ robot 271 to move the laser head 200 above the selected surface mount component 100 (S213). The controller 327 irradiates the selected surface mount component 100 with the laser beam according to the laser irradiation method determined in step S211 (S215).

  The controller 327 determines whether or not the mounting of all the surface mount components 100 is completed (S219). If not completed (NO in S219), the controller 327 selects the surface-mounted components 100 in the order programmed in advance, and repeatedly executes the processes in steps S213 to S215.

  If completed (YES in S219), the controller 327 controls the XYZ robot 271 to return the laser head 200 to the original position (S221). Finally, the controller 327 controls the printed wiring board transport device 251 so as to discharge the printed wiring board 107 on which all the surface mount components 100 are mounted (S223). Thereby, the printed wiring board 107 on which the surface mounting component 100 is mounted is manufactured.

  Such soldering by laser may be performed after soldering in a reflow furnace. More specifically, after a surface mount component having a high heat resistance temperature is soldered in a reflow furnace, the surface mount component having a low heat resistance temperature may be soldered by a laser.

  [Determining the cause of component standing up and laser irradiation method]

  Next, details of the step (S211) of determining the laser irradiation method described above will be described.

  FIG. 6 is a side view for explaining the cause of the occurrence of component standing and the like. As shown in FIG. 6, lands 103 a and 103 b are provided on the printed wiring board 107. Solders 104a and 104b are printed on the lands 103a and 103b. Only the solder 104b on the right side of the figure is melted by the laser beam. The electrodes 100a and 100b of the surface mount component 100 are soldered to the lands 103a and 103b, respectively.

  The weight of the surface-mounted component 100 is m, the length is L, the height is H, the width is W, the weight acceleration is g, and the surface tension of the molten solder is γ. A fulcrum for rotating the surface-mounted component 100 when the solder is melted is indicated by P in the figure.

  The distance from the right end of the land 103b to the fulcrum P is a, and the distance from the left end of the land 103b to the fulcrum P is b.

  An angle formed by a straight line connecting the right end of the land 103b and the uppermost side surface of the electrode 100b of the surface mount component 100 and the side surface of the electrode 100b of the surface mount component 100 is α. α is substantially equal to the angle formed by the molten solder 104b and the side surface of the electrode 100b. An angle formed by the bottom surface of the electrode 100b of the surface mount component 100 and the top surface of the land 103b is β.

At this time, moment T1 due to the surface tension γ (the force to rotate the surface-mounted component 100 clockwise about the fulcrum P to stand the surface-mounted component 100) is expressed by the following equation (1).

  On the lower surface of the surface-mounted component 100, a moment T2 due to the surface tension γ (a force acting in a direction opposite to the force for standing the component) is expressed by the following equation (2).

  T2 = γ cos β · Wb (2)

  Since cos β = 1 when β = 0, the moment T2 is expressed by the following equation (3).

  T2 = γWb (3)

  The moment T3 (force acting in the opposite direction to the force to stand the component) due to the weight of the surface-mounted component 100 is expressed by the following equation (4).

  T3 = mgLcosβ / 2 (4)

  Since cos β = 1 when β = 0, the moment T3 is expressed by the following equation (5).

  T3 = mgL / 2 (5)

  When the condition of T1> T2 + T3 is satisfied, there is a high possibility that component standing or the like will occur. That is, when α is larger than a predetermined threshold value (when the surface-mounted component 100 is shifted to the left side in the drawing and a << b), when the electrode 100b of the surface-mounted component 100 is soldered, the fulcrum P is used as an axis. The surface-mounted component 100 rotates clockwise, and component standing or the like easily occurs.

  As described above, the electrode (electrode 100a in FIG. 6) that floats up from the printed wiring board 107 due to the standing of components during soldering is referred to as “inferior electrode”, and the electrode on the opposite side (electrode 100b in FIG. 6). Called the “dominant electrode”. The inferior electrode is easily detached from the land, but the dominant electrode is not easily detached from the land. The adhesion force that acts between the inferior electrode 100a and the land 103a due to the surface tension γ of the molten solder 104a (the force that the inferior electrode 100a tends to adhere to the land 103a) is between the dominant electrode 100b and the land 103b due to the surface tension γ of the molten solder 104b. This is because it is weaker than the adhesion force acting on (the force that the dominant electrode 100b tries to adhere to the land 103b).

  Even when the amount of solder is large, the moment T1 is increased in the same manner as described above.

  [Vertical displacement of surface mount components]

  In FIG. 7A, the surface-mounted component 100 is placed on the printed wiring board 107 without shifting from the lands 103a and 103b. The solders 104a and 104b are also printed without shifting from the lands 103a and 103b. In this case, it is determined that no part standing or the like will occur.

  In FIG. 7B, the surface-mounted component 100 is placed on the printed wiring board 107 while being shifted to the left in the drawing. However, the solders 104a and 104b are printed without shifting from the lands 103a and 103b. When the surface mount component 100 is shifted to the left in the figure, the distance a becomes longer than the predetermined distance and the distance b becomes shorter than the predetermined distance on the right in the figure. Therefore, moment T1 is increased, but moment T2 is decreased. Thereby, the condition of T1> T2 + T3 is established. In this case, it is determined that component standing or the like will occur. When observing that the distance a on the electrode 100b side is equal to or greater than a predetermined distance, the electrode 100b is determined as the dominant electrode, and the opposite electrode 100a is determined as the inferior electrode.

  (1) Beam movement

  The single laser beam irradiation device 467a shown in FIG. 4 is used to move the single laser beam LB as shown in FIG. More specifically, the laser irradiation device 467a first irradiates the inferior electrode 100a and the land 103a with the laser beam LB. Next, the laser irradiation device 467a moves the laser beam LB from the inferior electrode 100a to the dominant electrode 100b. The laser irradiation device 467a irradiates the dominant electrode 100b and the land 103b with the laser beam LB.

  Since the laser beam LB is irradiated to the inferior electrode 100a side before the dominant electrode 100b side, the solder 104a on the inferior electrode 100a side melts faster than the solder 104b on the dominant electrode 100b side. For this reason, the adhesion force between the inferior electrode 100a and the land 103a increases, and the inferior electrode 100a does not float from the land 103a. As a result, no parts stand up.

  (2) Beam intensity

  Using two laser irradiation apparatuses 467a and 467b shown in FIG. 4, two laser beams LBa and LBb are simultaneously irradiated as shown in FIG. 9, and the intensity of the laser beam LBa is stronger than the intensity of the laser beam LBb. May be. More specifically, one laser irradiation device 467a irradiates the inferior electrode 100a and the land 103a with a laser beam LBa having an intensity Wa. At the same time, another laser irradiation device 467b irradiates the dominant electrode 100b and the land 103b with a laser beam LBb having an intensity Wb (Wa> Wb).

  Since the intensity Wa of the laser beam LBa is stronger than the intensity Wb of the laser beam LBb, the solder 104a on the inferior electrode 100a side melts faster than the solder 104b on the dominant electrode 100b side. As a result, there is no part standing or the like as described above.

  (3) Irradiation order

  Similarly, irradiation with the laser beams LBa and LBb may be started in order using two laser irradiation apparatuses 467a and 467b. More specifically, one laser irradiation device 467a starts irradiation of the inferior electrode 100a and the land 103a with the laser beam LBa at time t1. Another laser irradiation device 467b starts irradiation of the dominant electrode 100b and the land 103b with the laser beam LBb at a time t2 later than the time t1.

  Since the laser beam LBa is irradiated before the laser beam LBb, the solder 104a on the inferior electrode 100a side melts faster than the solder 104b on the dominant electrode 100b side. As a result, there is no part standing or the like as described above.

  [Vertical misalignment of solder]

  In FIG. 10A, the surface-mounted component 100 is placed on the printed wiring board 107 without shifting. The solders 104a and 104b are also printed on the lands 103a and 103b without shifting. In this case, it is determined that no part standing or the like will occur.

  In FIG. 10B, the solders 104a and 104b are printed shifted from the lands 103a and 103b to the right side in the figure. However, the surface-mounted component 100 is placed on the printed wiring board 107 without shifting from the lands 103a and 103b.

  The distance ratios a / b and a ′ / b ′ in FIG. 10B are the same as those in FIG. 10A. However, when the solder 104b starts to melt, the surface-mounted component 100 tries to rotate clockwise around the fulcrum P in the figure. Therefore, when the solder deviation is larger than the predetermined value, the soldering apparatus 50 determines that the component standing or the like will occur. If it is observed that the solder deviation is larger than a predetermined value, the electrode 100b is determined as the dominant electrode, and the opposite electrode 100a is determined as the inferior electrode.

  From the above, the following two rules are derived.

  (1) When a surface-mounted component is placed in a certain direction with a shift of a predetermined distance or more, the electrode on the shifted direction side becomes an inferior electrode.

  (2) When the solder is printed with a predetermined distance or more shifted in a certain direction, the electrode on the side opposite to the shifted direction becomes an inferior electrode.

  In consideration of at least one of the above (1) and (2), the soldering apparatus 50 determines the laser beam irradiation method.

  In FIG. 11A, the surface-mounted component 100 is placed on the printed wiring board 107 while shifting to the right in the figure. The solders 104a and 104b are also printed on the right side of the figure from the lands 103a and 103b. In this case, since there is no distance a at all, the distance a ′ is sufficient, so that the surface-mounted component 100 tries to get up by rotating counterclockwise on the fulcrum P as an axis. Therefore, the electrode 100a is determined as the dominant electrode, and the electrode 100b is determined as the inferior electrode.

  In FIG. 11B, the surface-mounted component 100 is placed on the printed wiring board 107 while shifting to the left in the figure. The solders 104a and 104b are printed shifted from the lands 103a and 103b to the right side in the figure. In this case, there is no distance a ′, but the distance a is sufficient. Therefore, the surface-mounted component 100 tries to get up by rotating clockwise around the fulcrum P in the figure. Therefore, the electrode 100b is determined as the dominant electrode, and the electrode 100a is determined as the inferior electrode.

  [Rotation deviation of surface mount components and solder]

  In FIG. 12A, the surface-mounted component 100 is placed on the printed wiring board 107 without shifting. The solders 104a and 104b are also printed on the land without shifting. In this case, it is determined that no component shift will occur.

  In FIG. 12B, the solders 104a and 104b are printed without shifting from the land. However, the surface-mounted component 100 is placed on the surface of the printed wiring board 107 so as to be shifted from the land (below the solders 104a and 104b) by an angle θ counterclockwise in the figure. In this case, the surface-mounted component 100 tries to rotate clockwise in the figure within the surface of the printed wiring board 107. Therefore, the electrode 100b is determined as the dominant electrode, and the electrode 100a is determined as the inferior electrode.

  In FIG. 12C, the solders 104a and 104b are printed offset from the lands 103a and 103b by an angle θ counterclockwise in the figure. The surface-mounted component 100 is also placed with the same angle θ shifted in the same direction as the solders 104a and 104b. In this case, the surface-mounted component 100 tries to rotate clockwise in the figure within the surface of the printed wiring board 107. Therefore, the electrode 100b is determined as the dominant electrode, and the electrode 100a is determined as the inferior electrode.

  In FIG. 12D, the solders 104a and 104b are printed offset from the lands 103a and 103b by an angle θ clockwise in the figure. The surface-mounted component 100 is mounted with a shift of an angle θ in the opposite direction to the solders 104a and 104b. In this case, the surface-mounted component 100 tries to rotate clockwise in the figure within the surface of the printed wiring board 107. Therefore, the electrode 100b is determined as the dominant electrode, and the electrode 100a is determined as the inferior electrode.

  [Ground land]

  The sizes of the lands 103a and 103b described above are almost the same. However, as shown in FIG. 13A, the grounding land 103g is larger than the normal land 103a. As shown in FIG. 13B, the solder resist 105 is applied on the printed wiring board so that the normal land 103a is exposed as it is and a part of the grounding land 103g is exposed as the land 103b. The solder printer 20 shown in FIG. 1 prints the solder pastes 104a and 104b on the exposed lands 103a and 103b, as shown in FIG. 13C. Finally, as shown in FIG. 13D, the surface mounters 40A and 40B place the surface mount component 100 on the lands 103a and 103b (not shown directly under the solder pastes 104a and 104b).

  In order to melt the solder of the lands 103a and 103b, when they are irradiated with a laser beam, heat is conducted as indicated by arrows in FIG. Since the area of the grounding land 103g including the land 103b is larger than the area of the normal land 103a, the heat of the land 103b is immediately dissipated around the area. On the other hand, the heat of the land 103a is not easily dissipated.

  FIG. 15A shows the relationship between the laser output and the temperature change of the normal land 103a. FIG. 15B shows the output of the laser and the temperature change of the land 103b which is a part of the grounding land 103g. The horizontal axis indicates time. The vertical axis represents the laser output and the land temperature.

  In any of FIG. 15A and FIG. 15B, the temperature of the land rises while the laser beam is irradiated. After the end of the laser beam irradiation, the land temperature decreases. However, since the area of the grounding land 103g is larger than the area of the normal land 103a, the grounding land 103g is less likely to be heated and cooled than the normal land 103b. Therefore, the electrode of the surface-mounted component placed on the grounding land 103g is an inferior electrode.

  [Effect of the embodiment]

  As described above, according to the preferred embodiment of the present invention, the surface-mounted component that is likely to stand up in the reflow process and the inferior electrode are specified based on the surface mounting component and the misalignment of the solder. The information is fed forward to the reflow process, and a laser beam is irradiated by an appropriate method so that no parts stand up in the reflow process. Since the solder on the inferior electrode side is melted quickly, and the adhesion force of the inferior electrode becomes strong quickly, it is possible to prevent the inferior electrode from coming off the land. As a result, a printed wiring board on which surface-mounted components are mounted can be manufactured with a high yield.

  [Other embodiments]

  The scanning speed (moving speed) or power of the laser beam may be controlled based on the melting point or amount of solder, the size of the land, or the like. Instead of the semiconductor laser, for example, a xenon lamp, an infrared lamp, a carbon dioxide laser, or a solid laser may be used.

  The embodiment of the present invention has been described above. However, the above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

Claims (8)

A method of manufacturing a printed wiring board on which surface-mounted components are mounted,
The surface mount component includes a plurality of electrodes,
The printed wiring board is provided corresponding to the plurality of electrodes, each including a plurality of lands to be soldered to the corresponding electrodes,
The manufacturing method includes:
Applying solder on the printed wiring board;
After applying the solder, placing the surface-mounted component on the printed wiring board;
Identifying an electrode whose adhesion between the electrode and the land due to the surface tension of the molten solder is weaker than the adhesion between the other electrode and the land;
Irradiating a light beam so that the solder on the specified electrode side is melted earlier than the solder on the other electrode side. The manufacturing method according to claim 1, further comprising:
Observing misalignment of the applied solder with respect to the land and / or misalignment of the electrode of the mounted surface mount component with respect to the land,
The specifying step is a manufacturing method in which an electrode having a weak adhesion is specified based on the observed displacement. The manufacturing method according to claim 1,
The plurality of lands are:
The first land,
A second land wider than the first land,
The specifying step is a manufacturing method in which an electrode corresponding to the second land is specified as an electrode having weak adhesion. The manufacturing method according to claim 1 or 2,
Irradiating the light beam comprises:
Starting irradiation of the light beam on the identified electrode at a first time;
Starting to irradiate the other electrode with the light beam at a second time later than the first time. It is a manufacturing method of Claim 3, Comprising:
The light beam applied to the identified electrode and the other electrode is generated by a single irradiation device,
A manufacturing method comprising the step of controlling the single irradiation device so that the light beam moves from the specified electrode to the other electrode. It is a manufacturing method of Claim 3, Comprising:
A light beam applied to the identified electrode is generated by a first irradiation device;
The manufacturing method in which the light beam irradiated to the said other electrode is produced | generated by the 2nd irradiation apparatus different from the said 1st irradiation apparatus. The manufacturing method according to claim 1 or 2,
Irradiating the light beam comprises:
Irradiating the identified electrode with a light beam at a first intensity;
Irradiating the other electrode with a light beam at a second intensity lower than the first intensity. A soldering device for soldering surface-mounted components to a printed wiring board,
The surface mount component includes a plurality of electrodes,
The printed wiring board is provided corresponding to the plurality of electrodes, each including a plurality of lands to be soldered to the corresponding electrodes, solder is applied on the printed wiring board, and the surface mount component is Placed on the printed wiring board,
The soldering apparatus is
Receiving means for receiving information for identifying an electrode whose adhesion between the electrode and the land due to the surface tension of the molten solder is weaker than the adhesion between the other electrode and the land;
And an irradiating means for irradiating a light beam so as to melt the solder on the electrode side specified by the information received by the receiving means faster than the solder on the other electrode side.

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