JP2020064884A - Mask design apparatus and method for determining mask opening size - Google Patents

Abstract

To provide a mask design apparatus and a method for determining a mask opening size, capable of appropriately performing design of a mask to be used for screen printing having a high printing difficulty level.SOLUTION: Determination of a mask opening size in mask design includes: determining a transfer rate of solder paste on the basis of at least a size of a mask opening part stored in a storage unit; calculating a transfer solder amount, an amount of solder paste to be printed on a land, by considering the transfer rate and mask opening volume calculated on the basis of the size of the mask opening part; determining whether or not the calculated transfer solder amount satisfies a required solder amount required for solder-bonding an object to be bonded on the land; and, when it is determined that the required solder amount is satisfied, taking the mask opening size used for calculating the transfer solder amount as a mask opening size for design. Thereby, design of a mask to be used for screen printing having a high printing difficulty level can be performed appropriately.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a mask designing apparatus for designing a mask used for screen printing and a mask opening dimension determining method in this mask designing.

  In a component mounting line for mounting electronic components on a board, screen printing is performed to supply solder for joining the components to the board. In screen printing, a squeegee is slid on the substrate with a mask having mask openings formed corresponding to the lands to which solder is to be supplied, and solder is applied to the lands through the mask openings. Transcribe. In soldering components, since it is required to supply an appropriate amount of solder according to the components to be joined, a technique for appropriately determining the shape / dimension of the mask opening has been conventionally proposed ( See, for example, Patent Document 1. In the prior art shown in this patent document example, it is shown that the solder shape for joining the land of the substrate and the electrode of the component is approximated to a triangular prism to obtain a reference volume, and the area of the mask opening is obtained based on this reference volume. ing.

Japanese Patent No. 3395732

  Along with the miniaturization of electronic devices and the sophistication of packaging density, miniaturization of components mounted on a board and narrowing of land are advancing. For this reason, in screen printing, the required accuracy of the proper amount of solder supplied to the land has become more sophisticated, and the printing difficulty has become more difficult. However, the conventional techniques including the above-mentioned patent document examples have not been able to deal with the design of a mask used in such screen printing having a high degree of difficulty in printing.

  Therefore, it is an object of the present invention to provide a mask designing apparatus and a mask opening dimension determining method which can appropriately design a mask used in screen printing having a high printing difficulty.

  A mask designing apparatus of the present invention is a mask designing apparatus for designing a mask used when a solder paste is printed on a land of a board by screen printing, and is based on at least a size of a mask opening stored in a storage unit. A transfer rate determining unit that determines a transfer rate of the solder paste, and a transfer that is the amount of the solder paste printed on the land in consideration of the transfer rate in the mask opening volume calculated based on at least the dimensions of the mask opening. A solder volume calculation unit that calculates a solder amount and a determination unit that determines whether or not the transferred solder amount satisfies a necessary solder amount required to solder-bond an object to be bonded to the land.

  A mask opening size determining method of the present invention is a mask opening size determining method for determining a mask opening size used when a solder paste is printed on a land of a substrate by screen printing, and at least the mask opening size stored in a storage unit. Transfer rate determining step for determining the transfer rate of the solder paste based on the dimension of the portion, and solder printed on the land in consideration of the transfer rate in the mask opening volume calculated based on at least the dimension of the mask opening. It includes a solder amount calculation step of calculating a transfer solder amount which is the amount of paste, and a determination step of determining whether the transfer solder amount satisfies a necessary solder amount necessary for solder-bonding an object to be bonded to the land. .

  According to the present invention, it is possible to appropriately design a mask used in screen printing, which has a high printing difficulty.

Block diagram showing the configuration of a mask designing apparatus according to an embodiment of the present invention Explanatory diagram of data stored in a storage unit of a mask designing apparatus according to an embodiment of the present invention Explanatory drawing of the data stored in the memory | storage part of the mask designing apparatus of one embodiment of this invention. Explanatory drawing which shows the cross-sectional shape of the mask opening part in the mask design by the mask design apparatus of one embodiment of this invention. The figure which shows the correlation table which shows the relationship of the printing difficulty index and the transfer rate in the mask design by the mask design apparatus of one embodiment of this invention. Calculation flow chart showing a mask opening size determination method according to an embodiment of the present invention

  Next, embodiments of the present invention will be described with reference to the drawings. First, the configuration of the mask designing device 1 will be described with reference to FIG. The mask designing device 1 is used for designing a mask used in printing a solder paste on a land of a board by screen printing in a mounting board manufacturing line.

  The mask design apparatus 1 includes a calculation unit 2 that executes calculations for mask design, and a storage unit 3 that stores various data used for mask design. Further, the arithmetic unit 2 is provided with a display unit 4 and an input unit 5. The display unit 4 is a display device such as a liquid crystal panel, and displays a processing step in the arithmetic processing by the arithmetic unit 2, a guide screen for inputting by the input unit 5 described below, and the like. The input unit 5 is an input device such as a keyboard or a touch panel switch built in the display unit 4, and inputs operation instructions and various data in the mask design calculation.

  The calculation unit 2 includes an information acquisition unit 2a, a transfer rate determination unit 2b, a solder volume calculation unit 2c, a determination unit 2d, and a correction unit 2e as internal processing functions. Each of these units executes the processing described below.

  The information acquisition unit 2a acquires, from the data stored in the storage unit 3, information necessary for determining the mask opening of the substrate to be designed. The transfer rate determining unit 2b performs a process of determining the transfer rate of the solder paste based on at least the dimensions of the mask openings stored in the storage unit 3. The solder volume calculation unit 2c performs a process of calculating the transfer solder amount, which is the amount of the solder paste printed on the land, by considering the transfer rate in the mask opening volume calculated based on at least the dimensions of the mask opening.

  The determination unit 2d performs a process of determining whether or not the transferred solder amount satisfies the necessary solder amount necessary for solder-bonding the electrodes of the component to be bonded to the land. When it is determined in this determination that the required solder amount is satisfied, the mask opening size used for calculating the transfer solder amount by the solder volume calculating unit 2c is set as the designed mask opening size. When the determination unit 2d determines that the transfer solder amount does not satisfy the required solder amount required for joining, the correction unit 2e performs a process of correcting the size of the mask opening so as to increase the transfer solder amount. .

  The storage unit 3 includes an initial Gerber data storage unit 3a, a modified Gerber data storage unit 3b, a board information storage unit 3c, a print difficulty index-transfer rate table storage unit 3d, a required solder amount storage unit 3e, and a mask information storage unit 3f. Have The initial Gerber data storage unit 3a and the corrected Gerber data storage unit 3b respectively store the initial Gerber data 30 and the corrected Gerber data 30 * shown in FIG. The initial Gerber data 30 is Gerber data set as an initial value in advance, and the corrected Gerber data 30 * is Gerber data set by correcting the initial value in the mask opening size determination process.

  The initial Gerber data 30 and the corrected Gerber data 30 * include the opening number 30a, the position coordinate 30b, the opening shape 30c, and the opening size 30d (or the corrected opening size 30d *). The opening number 30a is a number assigned to individually specify a plurality of mask openings in the target mask, and in the example shown here, the two mask openings whose opening number N is 001,002. Parts are illustrated.

  The position coordinate 30b indicates the relative position of the mask opening corresponding to each opening number N with respect to the reference point in the mask by plane coordinates (X, Y). That is, as shown in FIG. 2C, a plurality of mask openings P1 and P2 (here, two openings) are formed in the mask M, the opening shapes of which are “square” and “circular”, respectively. Of the mask openings P1, the position of the mask opening having the opening number N of 001 is specified by the plane coordinates (x1, y1). Further, of the mask openings P2, the position of the mask opening having the opening number N of 002 is specified by the plane coordinates (x2, y2).

  The opening shape 30c indicates the planar shape of the mask opening corresponding to each opening number N. Here, two types of opening shapes, “square” and “round”, are used. As shown in FIG. 2C, for the opening dimension 30d, the length dimension L and the width dimension W are defined for the mask opening portion P1 having the opening shape of "square", and the opening shape is "round". The diameter D of the mask opening P2 is defined. In the above-mentioned initial Gerber data 30 and corrected Gerber data 30 *, the opening dimension 30d * shown in FIG. 2B is that the length dimension L in the initial Gerber data 30 is changed to the length dimension L * by the correction. Is shown.

  The board information storage unit 3c stores the board information 31 shown in FIG. The board information 31 includes an opening number 31a, a land thickness 31b, a resist thickness 31c, and a silk thickness 31d. The opening number 31a is the same as the opening number 30a in the initial Gerber data 30, and is intended for two mask openings whose opening number N is 001,002. The land thickness 31b, the resist thickness 31c, and the silk thickness 31d are information on the shape element that specifies the uneven shape of the upper surface of the substrate corresponding to the mask opening (the mask opening P1 or the mask opening P2).

  In screen printing, as shown in FIG. 4A, the substrate B to be printed is brought into contact with the lower surface of the mask M. The land thickness 31b, the resist thickness 31c, and the silk thickness 31d indicate the land thickness tL, the resist thickness tR, and the silk thickness tS shown in FIG. 4A, respectively. The land thickness tL is the thickness of the land La to which the solder is transferred, and the resist thickness tR is the thickness of the resist R formed on the upper surface of the substrate B so as to surround the land La. The silk thickness tS indicates the thickness of the silk S formed on the upper surface of the resist R.

  4B and 4C schematically show the three-dimensional shape of the mask opening formed on the substrate B. FIG. 4B shows a three-dimensional shape of the mask opening P1 having an opening shape of "square". The mask opening P1 is shaped by a bottom area Ab obtained by multiplying the width dimension W by the length dimension L and an inner area As obtained by multiplying the mask outer circumference length obtained by the width dimension W and the length dimension L by the mask thickness tM. Is specified.

  An area ratio represented by inner area As / bottom area Ab is generally used as the print difficulty, which is an index of the difficulty of screen printing in the mask opening P1. That is, the larger the ratio of the inner area As to the bottom area Ab, the more difficult it is for the solder paste to come off. When the opening shape is a square, the aspect ratio tM / W indicating the ratio between the width dimension W and the mask thickness tM may be used as the print difficulty level. Also in this case, similarly, the larger the ratio of the mask thickness tM to the width W, the more difficult the solder paste is to come off.

  FIG. 4C shows a three-dimensional shape of the mask opening P2 whose opening shape is "round". As the print difficulty for the mask opening P2, the aspect ratio tM / D indicating the ratio between the diameter dimension D and the mask thickness tM is used as the print difficulty. Also in this case, as in the above-described example, the greater the ratio of the mask thickness tM to the diameter D, the more difficult the solder paste will come off. Also in this case, as in the above-described example, the greater the ratio of the mask thickness tM to the diameter D, the more difficult the solder paste will come off.

  In the screen printing for the substrate B having the uneven shape as shown in FIG. 4A on the upper surface, the silk thickness tS + resist thickness tR−land is provided between the lower surface of the mask M and the upper surface of the land La. There is a gap a represented by the thickness tL. Since this gap a communicates with the mask openings (mask openings P1 and P2) formed in the mask M, the aspect ratio (tM / W or In obtaining tM / D), the apparent aspect ratio (tM + a) / W or (tM + a) / D) obtained by adding the above-mentioned gap a to the mask thickness tM can be used as the print difficulty level.

  The printing difficulty index-transfer rate table storage unit 3d stores the printing difficulty index-transfer rate table 32 shown in FIG. The print difficulty index-transfer rate table 32 shows the relationship between the print difficulty index and the transfer rate described above, and represents empirically accumulated data in the form of a correlation table. Here, the transfer rate refers to the ratio of the volume of the solder that is actually transferred to the land in the plate separation that separates the substrate B from the mask M, out of the volume of the solder filled in the mask opening. Generally, the transfer rate decreases as the printing difficulty increases. That is, when transferring a desired amount of solder to the land to be printed, the higher the printing difficulty, the lower the transfer rate, and the transfer amount of the solder paste that is actually transferred decreases, so the internal volume of the mask opening is reduced. It is necessary to set it appropriately according to the transfer rate.

  That is, in the present embodiment, as the printing difficulty, the area ratio indicating the ratio of the bottom area Ab of the mask opening to the inner area As, or the width dimension W (or diameter dimension D) of the mask opening and the mask thickness tM. Or an apparent aspect ratio obtained by adding the gap a between the lower surface of the mask M and the upper surface of the land La to the mask thickness tM.

  FIG. 5 shows a specific example of the print difficulty index-transfer rate table 32 using the above-described three types of print difficulty. First, FIG. 5A shows a case where the area ratio (inner area As / bottom area Ab) is used as the printing difficulty. In this example, when the area ratio value is 1.5, the transfer rate α is 1.0, and when the area ratio value is 2.0, the transfer rate α is 0.8. That is, the transfer rate α decreases as the area ratio increases and the printing difficulty increases.

  Next, FIG. 5B shows a case where the aspect ratio (mask thickness tM / width dimension W (or diameter dimension D)) is used as the print difficulty. In this example, when the aspect ratio value is 0.5, the transfer rate β is 1.0, and when the aspect ratio value is 0.7, the transfer rate β is 0.8. That is, it is shown that the transfer rate β decreases as the aspect ratio increases and the printing difficulty increases.

  Further, FIG. 5C shows a case where the above-mentioned apparent aspect ratio (mask thickness (tM + a) / width dimension W (or diameter dimension D)) is used as the printing difficulty. In this example, when the apparent aspect ratio value is 0.8, the transfer rate γ is 1.0, and when the apparent aspect ratio value is 1.0, the transfer rate γ is 0.8. That is, this example also shows that the transfer rate γ decreases as the aspect ratio increases and the printing difficulty increases.

  The required solder amount storage unit 3e stores the required solder amount information 33 shown in FIG. The required solder amount information 33 includes the opening number 33a and the required solder amount 33b. The opening number 33a is the same as the opening number 30a in the initial Gerber data 30, and is intended for two mask openings whose opening number N is 001,002. Then, for each of these opening numbers, a required solder amount VS that is defined in advance according to the target solder joint portion is stored. That is, it is indicated that the lands corresponding to the mask openings having the opening numbers N of 001 and 002 need to be transferred by screen printing with the amounts of solder satisfying the required solder amounts VS1 and VS2, respectively.

  The mask information storage unit 3f stores the mask information 34 shown in FIG. The mask information 34 includes an opening number 34a and a mask thickness 34b. The opening number 34a is similar to the opening number 30a in the initial Gerber data 30, and is intended for two mask openings whose opening number N is 001,002. Then, the mask thickness tM of the mask M at the position where the mask opening is formed is stored for each opening number. Although the mask thickness tM is often the same for one mask M, in the case of a half-etch type mask M in which the upper surface of the mask M is partially cut, the mask thickness tM depends on the position of the mask opening. different.

  Next, a mask opening dimension determining method for determining the mask opening dimension used when the solder paste is printed on the land of the substrate by screen printing will be described with reference to the mask opening dimension determination flow shown in FIG.

  When the calculation is started (ST1), information is first acquired (ST2). That is, the initial Gerber data 30, the board information 31, the print difficulty index-transfer rate table 32, the required solder amount information 33, and the mask information 34 stored in the storage unit 3 are acquired. Then, the following arithmetic processing is sequentially executed based on the acquired information.

  First, the transfer rate of the solder paste is determined based on at least the dimensions of the mask openings stored in the storage unit 3 (transfer rate determining step: ST3). That is, the transfer rate is determined based on at least the print difficulty acquired based on the size of the mask opening. This calculation process is executed by the transfer rate determining unit 2b based on the initial Gerber data 30, the substrate information 31, and the mask information 34.

  Here, the transfer rate α based on the area ratio indicating the ratio between the bottom area Ab and the inner area As of the mask opening, and the transfer based on the aspect ratio indicating the ratio between the width dimension W of the mask opening and the mask thickness tM. Either the rate β or the transfer rate γ based on the apparent aspect ratio obtained by adding the gap a between the mask lower surface and the land upper surface to the mask thickness tM is applied to the mask opening. Determine the transcription rate to be used.

  Next, in the mask opening volume calculated based on at least the dimensions of the mask opening, the transfer solder amount which is the amount of the solder paste printed on the land La is calculated in consideration of the transfer rate determined in (ST3) (solder Quantity calculation step: ST4). Here, the solder volume calculation unit 2c calculates the mask opening volume calculated from the opening dimension 30d defined in the initial Gerber data 30 and the mask thickness tM of the mask information 34, and the land transfer rate determined in (ST3). The transfer solder amount actually transferred to La is calculated. Here, the transfer solder amount actually transferred is calculated by multiplying the mask opening volume by the transfer rate.

  Next, whether or not the calculated transfer solder amount is equal to or more than the required solder amount, in other words, the calculated transfer solder amount is the solder amount necessary for solder-bonding the electrode of the component to be bonded to the land La. The determination unit 2d determines whether or not the required solder amount stored in the required solder amount storage unit 3e is satisfied (determination step: ST5). When it is determined in this determination step that the required solder amount is satisfied, the mask opening size used for calculating the transfer solder amount in (ST4) is determined as the designed mask opening size (ST6). . Then, the determined designed mask opening size is stored in the corrected Gerber data storage unit 3b of the storage unit 3 as the corrected Gerber data 30 *.

  On the other hand, if it is determined in the determination step of (ST5) that the transfer solder amount does not satisfy the amount required for joining, information correction is executed (ST7). This information correction is executed by the correction unit 2e, and the size of the mask opening is corrected so that the amount of transferred solder transferred to the land La is increased (correction step). The corrected mask opening size is stored as the corrected Gerber data 30 * in the corrected Gerber data storage unit 3b of the storage unit 3 (see the opening size 30d * shown in FIG. 2B).

  Subsequent processing steps are then performed based on the modified mask opening size. That is, in the solder amount calculation step of (ST4), the transfer solder amount is calculated based on the mask opening size corrected in the correction step. The calculated transfer solder amount is again subjected to determination by the determination unit 2d in (ST5), and the same process is repeated until it is determined that the required solder amount is satisfied.

  After that, the storage unit 3 determines whether or not the arithmetic processing of all the components of the mask which is the target of the mask determination processing is completed (ST8). If all parts have not been finished, the process returns to (ST2) for the unprocessed part, information is acquired, and the same calculation process is repeatedly executed. When it is confirmed in (ST8) that the arithmetic processing has been completed for all components, the arithmetic processing for determining the mask opening size is terminated (ST9).

  As described above, in determining the mask opening size in the mask design shown in the present embodiment, the transfer rate of the solder paste is determined based on at least the size of the mask opening stored in the storage unit 3, and at least the mask opening is determined. Calculate the transfer solder amount that is the amount of solder paste printed on the land in consideration of the transfer rate to the mask opening volume calculated based on the dimension of the part, and the calculated transfer solder amount solders the object to be bonded to the land. It is determined whether the required solder amount for joining is satisfied, and if it is determined that the required solder amount is satisfied in this determination, the mask opening size used to calculate the transfer solder amount is used as the design mask. The opening size is set. As a result, it is possible to appropriately design a mask used in screen printing, which has a high printing difficulty.

  INDUSTRIAL APPLICABILITY The mask designing apparatus and the mask opening dimension determining method of the present invention have the effect of being able to appropriately design a mask used in screen printing, which has a high printing difficulty, and a field of designing a mask used in screen printing. Is useful in.

1 Mask Design Device M Mask P1, P2 Mask Opening W Width Dimension D Diameter Dimension B Substrate Ab Bottom Area As Inner Area tM Mask Thickness tR Resist Thickness tS Silk Thickness a Gap

Claims (12)

A mask design apparatus for designing a mask used when printing a solder paste on a land of a board by screen printing,
A transfer rate determination unit that determines the transfer rate of the solder paste based on at least the dimensions of the mask openings stored in the storage unit;
A solder volume calculation unit that calculates a transfer solder amount that is the amount of solder paste printed on the land in consideration of the transfer rate in a mask opening volume calculated based on at least the dimensions of the mask opening,
A mask designing apparatus, comprising: a determination unit that determines whether or not the transferred solder amount satisfies a necessary solder amount required for solder-bonding an object to be bonded to the land.   The mask designing apparatus according to claim 1, wherein, when it is determined that the transfer solder amount is satisfied, the mask opening dimension used for calculating the transfer solder amount is set as a designed mask opening dimension.   The mask designing device according to claim 1, wherein the transfer rate determining unit determines the transfer rate based on at least the print difficulty acquired based on the dimension of the mask opening.   The printing difficulty is an area ratio indicating a ratio of a bottom area to an inner area of the mask opening, or an aspect ratio indicating a ratio of a width dimension of the mask opening to a mask thickness, or the mask thickness to a mask lower surface. 4. The mask designing apparatus according to claim 1, wherein the mask aspect ratio is an apparent aspect ratio obtained by taking into consideration a gap between the land and the land upper surface.   The mask design apparatus according to claim 1, wherein the solder volume calculation unit calculates the transfer solder amount by multiplying the mask opening volume by the transfer rate. The determining unit includes a correction unit that corrects the dimensions of the mask opening so that the transfer solder amount increases when it is determined that the transfer solder amount does not satisfy the amount necessary for joining.
The mask design apparatus according to claim 1, wherein the solder volume calculation unit calculates the transfer solder amount based on the mask opening size corrected by the correction unit. A mask opening size determining method for determining a mask opening size used when a solder paste is printed on a land of a board by screen printing,
A transfer rate determining step of determining a transfer rate of the solder paste based on at least the dimensions of the mask opening stored in the storage section;
A solder amount calculation step of calculating a transfer solder amount which is the amount of solder paste printed on the land in consideration of the transfer rate in the mask opening volume calculated based on at least the dimensions of the mask opening,
And a step of determining whether the transfer solder amount satisfies a necessary solder amount necessary for solder-bonding an object to be bonded to the land.   8. The mask opening dimension determining method according to claim 7, wherein, when it is determined that the transfer solder amount is satisfied in the determination step, the mask opening dimension used for calculating the transfer solder amount is set as a designed mask opening dimension.   9. The mask opening size determining method according to claim 7, wherein in the transfer ratio determining step, the transfer ratio is determined based on at least the print difficulty acquired based on the size of the mask opening.   The printing difficulty is an area ratio indicating a ratio of a bottom area to an inner area of the mask opening, or an aspect ratio indicating a ratio of a width dimension of the mask opening to a mask thickness, or the mask thickness to a mask lower surface. 10. The mask aperture dimension determining method according to claim 7, wherein the mask aperture dimension is an apparent aspect ratio obtained by taking into consideration a gap between the mask and the land upper surface.   11. The mask opening size determining method according to claim 7, wherein in the solder amount calculating step, the transfer solder amount is calculated by multiplying the mask opening volume by the transfer rate. In the determination step, further comprising a correction step of correcting the dimensions of the mask opening so as to increase the transfer solder amount when it is determined that the transfer solder amount does not satisfy the amount required for joining,
The mask opening size determining method according to claim 7, wherein in the solder amount calculating step, the transfer solder amount is calculated based on the mask opening size corrected in the correcting step.

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