JP2007189101A - Method for mounting electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure a displacement of a printed solder paste, and to prevent an occurrence of a mounting failure of an electronic component at the time of reflow. <P>SOLUTION: At the time of mounting a surface mount component 30 on a board 10, the solder paste is printed on a dummy land 22 for recognizing the position of the solder paste as well as on a board land 12. The displacement of the solder 22 for recognizing the position printed on the dummy land 14 to the dummy land 14 is measured, and on the basis of the measurement result, the mounting target position of the surface mount component 30 to be mounted on the board land 12 is compensated, and the component 30 is mounted, then heated to be soldered in a reflow furnace. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic component mounting method, and more particularly to a technique for surface-mounting an electronic component on a substrate.

  When surface mounting electronic components on a board, the board is mounted on a board fixing jig, a solder paste is printed on a predetermined land on the board using a metal mask, and then the electronic parts are placed on the board (solder paste). After mounting on the top), the board is transferred to a reflow furnace, where it is heat-treated to solder the electronic components.

  However, solder printing may be displaced depending on the accuracy of the mounting position of the substrate on the substrate fixing jig. If the solder printing is misaligned and the electronic component is mounted on the land side, in many cases, the reflow process may cause a defective mounting or misalignment of the electronic component or a mounting defect such as a bridge of the lead component.

  Patent Document 1 proposes a surface component mounting method for solving the above problems.

The surface component mounting method described in Patent Document 1 detects the position of a pattern mark formed on a substrate, detects a target mounting position of an electronic component based on the detected position, and based on the target mounting position. The solder paste is printed, and the paste mark is printed at a position different from the position of the pattern mark. Subsequently, the position of the paste mark is detected, the amount of error between the design value of the position of the pattern mark and the position of the paste mark is calculated, and the target mounting position of the electronic component is corrected with the calculated amount of error. The electronic component is mounted on the substrate based on the corrected target mounting position.
JP-A-7-22791

  However, the surface component mounting method described in Patent Document 1 prints a paste mark at a position different from the pattern mark formed on the substrate, and detects the position of each mark by image recognition. There is a problem that the field of view of the image pickup apparatus for picking up an image of the pattern mark and the paste mark at the same time has to be widened, and the image pickup apparatus becomes large or the mark position detection accuracy decreases.

  Further, since the paste mark is printed on the solder resist of the substrate, there is a problem that the wettability is poor, and the paste mark becomes dust without being fixed to the substrate after reflow.

  The present invention has been made in view of such circumstances, and accurately measures a positional deviation between a board land for mounting an electronic component formed on a board and a solder paste printed on the board land. An object of the present invention is to provide an electronic component mounting method capable of preventing the occurrence of defective mounting of electronic components during reflow.

  In order to achieve the above object, an invention according to claim 1 is an electronic component mounting method for surface-mounting an electronic component on a substrate, printed on the substrate land together with a predetermined substrate land for mounting the electronic component. Printing a solder paste on a predetermined board land and dummy land of the board, and printing on the dummy land and the dummy land. A step of measuring a positional deviation with respect to the position-recognizing solder, a step of mounting an electronic component by correcting a mounting target position of the electronic component mounted on the predetermined board land according to the measured positional deviation, and And a step of heating and soldering the substrate on which the electronic component is mounted in a reflow furnace.

  That is, a dummy land for recognizing the position of the solder paste to be printed is formed on the substrate to which the present invention is applied. In this dummy round, a substrate recognition mark (copper foil exposed from the solder resist on the substrate surface) formed on the substrate can be applied. When the solder paste is printed using the mask, the solder paste (position recognition solder) is also printed on the dummy land. The positional deviation between the dummy land and the position recognition solder is measured, and the measured positional deviation is regarded as the positional deviation of the printed solder paste on the board land.

  When mounting various electronic components on the board on which the solder paste is printed, the mounting target position (position corresponding to the board land) of each electronic component on the board is corrected according to the measured displacement. Mount electronic components. That is, the electronic component is not mounted according to the position of the board land, but is mounted according to the printed solder paste. Thereafter, the substrate on which the electronic component is mounted is subjected to heat treatment in a reflow furnace in accordance with a predetermined temperature profile to perform soldering. Thereby, even if the solder paste is misprinted with respect to the board land, mounting defects can be reduced, and the yield can be improved.

  In the electronic component mounting method according to claim 1, when a plurality of substrates are fixed to one substrate fixing jig and the electronic components are mounted on the plurality of substrates, the electronic components are mounted on the plurality of substrates. The position deviation between the dummy land and the position recognition solder is individually measured, and the mount target position of the electronic component mounted on the predetermined board land on each board is individually corrected according to the measured position deviation. It is characterized by mounting electronic components. When a plurality of substrates are fixed on one substrate fixing jig, the fixing position of the substrate is not fixed, and an error occurs for each substrate. When solder printing is performed in this state, the solder printing shift and the shift direction are different for each substrate. Therefore, the positional deviation of the solder paste is recognized for each substrate, and the electronic component mounting target position is individually corrected in accordance with the positional deviation in each substrate to mount the electronic component.

  According to a third aspect of the present invention, in the electronic component mounting method according to the first or second aspect, one side or the diameter of the position recognition solder is 0.3 mm or more. If the position-recognition solder (mask opening) is too small, the ability to remove the solder paste deteriorates and the position-recognition accuracy decreases. However, one side or the diameter of the position-recognition solder should be 0.3 mm or more. Thus, it is possible to print the position recognition solder with high accuracy, and to improve the solder position recognition accuracy.

  According to a fourth aspect of the present invention, in the electronic component mounting method according to the first aspect, at least two or more dummy lands are formed on the substrate, and the position confirmation solder is printed on each dummy land, In addition, the positional deviation between the dummy land and the position recognition solder is measured.

  5. The electronic component mounting method according to claim 4, wherein a plurality of positional deviations measured for each of the two or more dummy lands are averaged, and the average positional deviation is corrected for the mount target position. It is characterized by being used for. Thereby, the solder position recognition accuracy can be improved.

  According to a sixth aspect of the present invention, in the electronic component mounting method according to the fourth aspect, the predetermined board land of the board and the board land on the board land based on a plurality of positional shifts measured for each of the two or more dummy lands. The position deviation from the printed solder paste is calculated individually, and the electronic component is mounted by individually correcting the mount target position of each electronic component mounted on a predetermined board land according to the calculated position deviation. It is characterized by. In other words, it is possible to recognize a rotational displacement in the plane between the substrate and the mask based on a plurality of positional displacements, and to correct the mounting position of the electronic component in consideration of the rotational displacement.

  According to a seventh aspect of the present invention, in the electronic component mounting method according to the first aspect, with respect to the measured positional deviation, the mounting target position of the electronic component is set to the solder paste side by 1/3 to 1 times the positional deviation. It is characterized by correcting and mounting electronic components. If the printed solder paste and the board land are misaligned, the molten solder at the time of reflow is drawn toward the board land. Therefore, in consideration of the movement of the molten solder, the mounting target position of the electronic component is corrected to the solder paste side by 1 to 1 to 1 times the positional deviation without mounting the electronic component accurately on the printed solder paste. It is preferable. Note that 1/3 is an empirical value at which no mounting failure occurs after reflow.

According to an eighth aspect of the present invention, in the electronic component mounting method according to the first or third aspect, the size of the dummy land is larger than the size of the position recognition solder.
As a result, the contour of the dummy land can be prevented from being hidden by the position confirmation solder, and the position confirmation accuracy of the dummy land and the position confirmation solder can be improved.

  According to a ninth aspect of the present invention, in the electronic component mounting method according to the first aspect, the dummy lands and the position recognition solder each have a shape having a straight line. This improves the position recognition accuracy between the dummy land (substrate) and the printed position confirmation solder (mask) (particularly, the accuracy of recognition of the angle deviation between the substrate and the mask).

  According to the present invention, since the position confirmation solder is simultaneously printed on the dummy land, the positional deviation between the dummy land and the printed position confirmation solder can be accurately measured. Since the mounting position of the electronic component is corrected, it is possible to prevent the mounting failure of the electronic component in the reflow process.

  Preferred embodiments of an electronic component mounting method according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a flowchart showing an electronic component mounting procedure in the electronic component mounting method according to the present invention.

[Step S1]
In step S1, a solder paste is printed on the substrate using a metal mask. That is, the substrate is mounted on a substrate fixing jig (carrier board) so that the substrate can be stably held, and is conveyed to a solder printer. The positioning hole formed in the substrate is engaged with the positioning pin of the substrate fixing jig, and thereby the substrate is positioned on the substrate fixing jig. However, the accuracy and backlash between the positioning hole and the positioning pin cause the substrate to be positioned. There is a variation in the mounting position accuracy.

  The solder printer has a metal mask in which a mask opening corresponding to a substrate land of the substrate is formed, positions the metal mask on the substrate, and supplies solder paste onto the metal mask with a dispenser or the like. Then, by sliding the squeegee on the metal mask, the mask opening is filled with the solder paste, and then the metal mask is pulled away from the substrate to print the solder paste on the substrate land of the substrate.

  FIG. 2 is a plan view of a substrate on which a solder paste is printed by the solder printer.

  A substrate land 12 connected to a wiring pattern (not shown) on the substrate is formed on the substrate 10, and a dummy land for position recognition (hereinafter simply referred to as “dummy land”) 14 is provided. Is formed.

  The dummy land 14 is a copper foil portion exposed from the solder resist on the surface of the substrate, and may be formed exclusively, or a substrate position recognition mark previously formed on the substrate may be used. The dummy land 14 may be formed on a discarded substrate (a discarded substrate connected to the single substrate by a perforation) at the periphery of the substrate, or may be formed on a single substrate.

  The solder printing machine prints the solder paste on the board land 12 and also prints the solder paste on the dummy land 14.

  In FIG. 2, 20 indicates a solder paste (printed solder paste) printed on the substrate land 12, and 22 indicates a solder paste (position recognition solder) printed on the dummy land 14. Further, FIG. 2 shows a case where the printed solder paste 20 and the position recognition solder 22 are printed out of position with respect to the substrate land 12 and the dummy land 14, respectively. This misalignment is caused by misalignment between the substrate 10 and the metal mask.

  FIG. 3 is a diagram illustrating an example of the sizes of the dummy land and the position recognition solder.

  As shown in the figure, each of the dummy land 14 and the position recognition solder 22 has a square shape, where one side of the dummy land 14 is A and one side of the position recognition solder 22 is B. Both have a relationship of A> B. Thus, the contour of the dummy land 14 can be prevented from being hidden as much as possible by the position confirmation solder 22. When the positional deviation between the substrate and the metal mask (that is, the printing deviation of the solder paste) is within an allowable range, the size of both is determined so that the position recognition solder 22 is positioned inside the dummy land 14. It is preferable to do.

  The dimension B of the position confirmation solder 22 is preferably 0.3 mm or more. This is because if the position-recognizing solder 22 (mask opening) is less than 0.3 mm, the removability of the solder paste deteriorates. When the position confirmation solder has a circular shape, the diameter of the representative dimension is set to 0.3 mm or more.

[Step S2]
In step S2, the positional deviation of the printed solder paste is measured. In other words, the position confirmation solder 22 is imaged together with the dummy land 14 shown in FIG. 2 by the imaging camera, and the contour of the dummy land 14 and the contour of the position confirmation solder 22 are detected from the image data acquired by this imaging. . Since the dummy land 14 is a copper foil, the brightness is high, and the solder resist on the substrate surface in the background has a low brightness. Therefore, the contour of the dummy land 14 can be easily detected. Similarly, since the luminance difference between the dummy land 14 and the position confirmation solder 22 is large, the contour of the position confirmation solder 22 can be easily detected.

Based on the contour of the dummy land 14 and the contour of the position confirmation solder 22 detected as described above, the center positions O ₁ and O ₂ of each contour are obtained, and the shift amounts Δx and Δy of the position O ₂ with respect to the position O ₁ are obtained. Is calculated.

  The positional deviation (Δx, Δy) between the dummy land 14 and the position recognition solder 22 measured in this way is regarded as the positional deviation of the printed solder paste 20 on the board land 12.

  The measurement of the positional deviation of the printed solder paste may be performed by a solder printing inspection machine, or may be performed by a solder printing machine or a measuring machine attached to the mounter.

[Step S3]
In step S3, an electronic component is mounted on the substrate 10 on which the solder paste is printed. That is, the substrate 10 on which the solder paste is printed is conveyed to the mounter. The mounter has position data (electronic component mount target position data) for mounting each electronic component to be surface-mounted on the substrate land 12 of the substrate 10 positioned with respect to the mounter. The surface mount component can be mounted on the board land 12 with high accuracy based on the position data.

  The mounter corrects the mount target position data based on the measured displacement (Δx, Δy) of the printed solder paste 20, and mounts the surface mount component based on the corrected mount target position data.

  FIG. 4 is a side view showing a state where the surface mount component is mounted on the substrate by the mounter. As shown in the figure, the surface-mounted component 30 is not mounted according to the position of the board land 12 but is mounted according to the printed solder paste 20. That is, the surface mounting component 30 is mounted with the mounting target position shifted by the positional deviation (Δx, Δy) of the printed solder paste 20. FIG. 4 shows a state in which the surface-mounted component 30 is shifted by a one-dimensional displacement (Δx), but the displacement occurs in two dimensions.

[Step S4]
In step S4, the surface mount component 30 mounted on the substrate 10 is soldered. That is, the substrate 10 on which the surface mount component 30 is mounted is transferred to a reflow furnace. In the reflow furnace, the substrate 10 is heat-treated according to a predetermined temperature profile, and the surface-mounted component 30 is soldered by melting and solidifying the printed solder paste 20.

  Even if the printed solder paste 20 is displaced with respect to the board land 12, the surface mounting component 30 is mounted in accordance with the printed solder paste 20, so that mounting defects can be reduced and the yield can be improved. be able to.

  Hereinafter, other embodiments and modifications of the electronic component mounting method according to the present invention will be described.

  FIG. 5 shows a case where a plurality of substrates are fixed to one substrate fixing jig. The parts common to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 5 shows a case where four substrates 10 of the same type are mounted on one substrate fixing jig 40. The fixed positions of the four substrates 10 are not fixed (there is variation), and the printing misalignment and misalignment direction of the printed solder paste 20 printed on each substrate 10 are different for each substrate 10.

  Therefore, the measurement of the positional deviation of the printed solder paste in step S2 in FIG. 1 is performed for each substrate 10, and the correction of the mount target position when mounting the surface mount component in step S3 is measured for each substrate. This is done according to the misalignment of the printed solder paste.

  Thereby, even if the printing misalignment and misalignment direction of the printed solder paste 20 are different for each of the four substrates 10 mounted on one substrate fixing jig 40, the surface mount component is mounted on the printed solder paste 20 with high accuracy. be able to.

  FIG. 6 is a plan view showing another embodiment of a substrate on which a solder paste is printed. The parts common to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 6, two dummy lands 14 are formed on the upper left and lower right of the substrate 10 ′, and the position confirmation solder 22 is printed on each dummy land 14.

  The measurement of the positional deviation of the printed solder paste in step S2 in FIG. 1 is performed for each of the two dummy lands 14, and two measurement results of the positional deviation between the dummy land 14 and the position confirmation solder 22 are obtained.

  The two positional deviations measured in this way are averaged, and the averaged positional deviation is used for correcting the mount target position of the surface mount component. Thus, by calculating the average of a plurality of misalignments, the misalignment measurement accuracy and reliability can be improved.

  Further, by measuring two positional shifts on the two dummy lands 14, it is also possible to measure the rotational shift in the plane between the substrate 10 and the metal mask. Therefore, the mount target position of the surface mount component can be individually corrected from the positional relationship between the dummy land 14 and the substrate land 12 in consideration of the shift in the rotation direction.

  In the embodiment shown in FIG. 6, the case where the two dummy lands 14 are formed on the substrate 10 has been described. However, the number of dummy lands is not limited to this, and may be three or more.

  FIG. 7 is a view showing another embodiment in which the mount target position is corrected and the surface mount component is mounted.

  That is, in the embodiment shown in FIG. 4, the mounting position of the surface mounting component 30 is shifted by the amount of deviation of the printed solder paste 20, and the surface mounting component 30 is mounted on the printed solder paste 20. In this embodiment, the surface mount component 30 is mounted at a position intermediate between the board land 12 and the printed solder paste 20.

  In the example shown in FIG. 7, the printed solder paste 20 is printed with a positional deviation of Δx in the left-right direction and Δy in the up-down direction with respect to the center of the board land 12.

When mounting the surface mount component 30, the mount shift amount (D _x , D _y ) is smaller than the positional shift (Δx, Δy) of the printed solder paste 20 with respect to the mount target position (position of the board land 12). Only the surface mount component 30 is shifted and mounted.

That is, the mount shift amount (D _x , D _y ) of the surface mount component 30 satisfies the following expression with respect to the positional shift (Δx, Δy) of the printed solder paste 20.

(Equation 1)
(1/3) Δx <D _x <Δx, (1/3) Δy <D _y <Δy
If the board land 12 and the printed solder paste 20 are misaligned, the molten solder melted during reflow is drawn toward the board land 12 side. Therefore, it is preferable to determine the amount of mounting shift of the surface mount component 30 in consideration of the movement of the molten solder. Incidentally, the numerical value of 1/3 on the lower limit side for determining the mount shift amount is a value empirically obtained from the presence or absence of mounting failure after reflow.

FIG. 1 is a flowchart showing an electronic component mounting procedure in the electronic component mounting method according to the present invention. FIG. 2 is a plan view showing an example of a substrate on which a solder paste is printed. FIG. 3 is a diagram illustrating an example of the sizes of the dummy land and the position recognition solder. FIG. 4 is a side view showing a state in which the surface mount component is mounted on the substrate. FIG. 5 is a plan view showing a state in which a plurality of substrates are fixed to one substrate fixing jig and solder paste is printed. FIG. 6 is a plan view showing another embodiment of a substrate on which a solder paste is printed. FIG. 7 is a plan view of a main part used for explaining another embodiment for mounting the surface mount component by correcting the mount target position.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 10 '... Board | substrate, 12 ... Board land, 14 ... Dummy land for solder position recognition, 20 ... Printed solder paste, 22 ... Solder for position confirmation, 30 ... Surface mount component, 40 ... Board fixing jig

Claims (9)

In an electronic component mounting method for surface mounting electronic components on a substrate,
Using a board on which a dummy land for position recognition of a solder paste printed on the board land is formed together with a predetermined board land for mounting an electronic component,
Printing a solder paste on predetermined substrate lands and dummy lands of the substrate;
Measuring a positional deviation between the dummy land and the position recognition solder printed on the dummy land;
Mounting the electronic component by correcting the mounting target position of the electronic component mounted on the predetermined board land in accordance with the measured displacement; and
Heating and soldering the substrate on which the electronic component is mounted in a reflow furnace; and
An electronic component mounting method comprising:   When multiple substrates are fixed to a single substrate fixing jig and electronic components are mounted on multiple substrates, the positional deviation between the dummy lands on the multiple substrates and the position recognition solder is measured individually. 2. The electronic component according to claim 1, wherein the electronic component is mounted by individually correcting a mount target position of the electronic component mounted on a predetermined substrate land on each substrate in accordance with the individual positional deviation. Component mounting method.   3. The electronic component mounting method according to claim 1, wherein one side or the diameter of the position recognition solder is 0.3 mm or more.   The substrate is formed with at least two dummy lands, the position confirmation solder is printed on each dummy land, and the positional deviation between the dummy land and the position recognition solder is measured for each dummy land. The electronic component mounting method according to claim 1.   5. The electronic component mounting method according to claim 4, wherein a plurality of positional deviations measured for each of the two or more dummy lands are averaged, and the averaged positional deviation is used for correcting the mount target position. .   Based on a plurality of positional deviations measured for each of the two or more dummy lands, the positional deviation between the predetermined board land of the board and the solder paste printed on the board land is individually calculated, and the calculated position 5. The electronic component mounting method according to claim 4, wherein the electronic component is mounted by individually correcting a mount target position of each electronic component mounted on a predetermined board land according to the deviation.   The electronic component is mounted by correcting the mounting target position of the electronic component to the solder paste side by 1/3 to 1 times of the measured positional displacement. Electronic component mounting method.   4. The electronic component mounting method according to claim 1, wherein a size of the dummy land is larger than a size of the position recognition solder. 2. The electronic component mounting method according to claim 1, wherein each of the dummy land and the position recognition solder has a shape having a straight line.

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