JP2002185103A - Method for evaluating flatness of electrode pads on mounting surface of mounting substrate - Google Patents

Abstract

(57) [Problem] It is difficult to obtain the flatness of the surface formed by the electrode pads reflecting the actual mounting process by the conventional method for evaluating the flatness of the mounting surface of a mounting board, and There was a problem that the evaluation was deviated from the degree. SOLUTION: A mounting substrate 3 having a plurality of electrode pads 4 on a mounting surface of a semiconductor device 1 is measured at n measurement points (where n is an integer of 4 or more) among the electrode pads 4. A plane obtained by using the least squares method from the n sets of three-dimensional coordinate data is set as a first virtual plane, and then the point having the lowest height from the first virtual plane is removed (n-1).
A plane obtained from the set of three-dimensional coordinate data by using the least squares method is defined as a second virtual plane, and the same process is repeated in order until three sets of three-dimensional coordinate data are obtained. After the obtained (n-2) th virtual plane is obtained, the distance of the n points viewed from the (n-2) th virtual plane is obtained as the evaluation height.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting method for mounting a semiconductor device such as a semiconductor device or a semiconductor device in which a semiconductor device is housed in a package for housing a semiconductor device by a so-called flip-chip mounting method. The present invention relates to a flatness evaluation method suitable for evaluating the flatness of a mounting surface of a mounting board having a surface.

[0002]

2. Description of the Related Art In recent years, as a method of mounting a semiconductor device such as a semiconductor device or a semiconductor device containing a semiconductor device on a mounting substrate used as a wiring substrate such as a circuit board or a package for housing a semiconductor device, a so-called flip-chip mounting method is used. The law is becoming heavily used. This technique is
For example, a protruding electrode made of gold, a solder material, or the like is provided on an electrode on a mounting surface side of a semiconductor device, and an electrode is provided at a position facing the protruding electrode on a mounting surface of a mounting substrate on which the semiconductor device is mounted. Pads are provided, and the semiconductor device is mounted after positioning the projecting electrodes of the semiconductor device and the electrode pads of the mounting substrate, and then heating and pressing the semiconductor device. The projection electrode and the electrode pad are joined by applying ultrasonic energy, and the semiconductor device is mounted on the mounting substrate face-down.

In such flip-chip mounting, various methods are used for mechanically bonding and electrically connecting the electrode pads of the mounting substrate and the protruding electrodes of the semiconductor device.

For example, as shown in a side view of FIG. 4A, a semiconductor element 1 as a semiconductor device is prepared by applying, for example, a silver paste 5 to the tip of a protruding electrode 2 formed on the lower surface thereof. 3 is placed in contact with the electrode pad 4 formed in the element mounting area on the upper surface of the semiconductor element 1, and as shown in the same side view in FIG. Means 6) There is a method in which the projecting electrode 2 and the electrode pad 4 are connected via the silver paste 5 or the like by heating and pressing by 6.

Further, the protruding electrodes of the semiconductor element are formed of gold, and the surfaces of the electrode pads formed on the mounting surface of the mounting board are also formed of gold. The protruding electrodes and the electrodes are formed without using a silver paste or a solder material. There is also a method in which the pads are aligned, ultrasonic waves are applied by a tool capable of applying ultrasonic waves to the pads, and the pads are connected only by ultrasonic waves and heating.

[0006]

However, in order to mount a semiconductor device with high reliability by these methods, it is necessary to ensure that the heights of the projecting electrodes of the semiconductor device are uniform and that the warpage of the mounting substrate is high. It is very important that the height of the electrode pads on the mounting board is uniform. For this reason, it is necessary to determine the quality of a product based on an index indicating how uniform the heights of the electrode pads on the mounting board are.

Therefore, considering the actual mounting process, when the semiconductor device is pressed against the mounting substrate, first,
The plane formed by the mounting surface side surface of the semiconductor device, that is, the plane formed by the tips of the protruding electrodes on the lower surface approaches the mounting substrate, and among the electrode pads on the mounting surface of the mounting substrate, is the closest to the lower surface of the semiconductor device. In other words, after the semiconductor device is supported by the three highest electrode pads, the other protruding electrodes are brought into contact with and bonded to the electrode pads by deformation of those protruding electrodes. At this time, the last contact between the protruding electrodes and joining is the electrode pad having the lowest height on the mounting surface. Therefore, in evaluating the flatness of the mounting substrate, it can be said that it is desirable to use, as an index, the height of the lowest electrode pad as viewed from a virtual plane sharing the highest three electrode pads.

On the other hand, conventionally, as an index of the flatness of the mounting board, a virtual plane is provided which fixes three specific electrode pads on the mounting surface of the mounting board and shares the three points.
The height of the lowest point among the heights of the measurement points corresponding to the respective electrode pads as viewed from the virtual plane was determined, and this was used as an index.

As another index of the flatness of the conventional mounting substrate, a plane coordinate and a height in a three-dimensional coordinate measuring system of each electrode pad point on the mounting surface of the mounting substrate are measured as a set. After obtaining a virtual plane by the least square method using the obtained three-dimensional coordinate data, the difference between the highest point and the lowest point among the heights of the electrode pads viewed from the virtual plane is defined as flatness. Was used as an index.

However, in the conventional method for evaluating the flatness of a mounting substrate as in the former, three points for determining a virtual plane for evaluating the flatness are determined at a predetermined position on the mounting plane. And the virtual plane sharing the three points is not always obtained as an effective plane for reflecting the actual mounting process. In some cases, the virtual plane may be extremely inclined. there were.
For this reason, the distance from the extremely inclined virtual plane to each point as viewed from the virtual plane greatly varies, and the flatness index obtained thereby greatly varies. As a result,
There is a problem that the flatness of the mounting surface is evaluated differently from the actual flatness.

In the conventional method for evaluating the flatness of a mounting substrate as described above, the obtained virtual plane does not reflect the actual mounting process, but is simply obtained as an average plane. However, as the flatness obtained thereby, an evaluation result that the flatness is good is obtained, and as a result, there is a problem that the evaluation is deviated from the actual flatness. .

The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to obtain an index of flatness which reflects an actual mounting process on a mounting surface of a mounting substrate. The mounting of the mounting substrate, which can easily and reliably determine the quality of the semiconductor device mounted on the electrode pad on the mounting surface and the quality of the product obtained by mounting the semiconductor device on the mounting substrate. An object of the present invention is to provide a method for evaluating flatness of an electrode pad on a surface.

[0013]

According to the present invention, there is provided a method for evaluating the flatness of an electrode pad on a mounting surface of a mounting substrate, comprising the steps of: mounting a plurality of electrodes on a mounting surface on which a semiconductor device is mounted; For a mounting board with pads,
For n measurement points (where n is an integer of 4 or more) selected so as to be dispersedly arranged on the mounting surface among the electrode pads, the plane coordinates and the height in the three-dimensional coordinate measurement system are set to one. Measured as a set and the resulting n
A plane obtained by using the least squares method from the set of three-dimensional coordinate data is obtained as a first virtual plane, and then the points having the lowest height from the first virtual plane among the n points are removed (n
-1) A plane obtained by using the least squares method from the set of three-dimensional coordinate data is obtained as a second virtual plane, and points having the lowest height from the virtual plane obtained immediately before are sequentially removed in the same manner. This process is repeated until three sets of three-dimensional coordinate data are obtained.
After obtaining the (n-2) th virtual plane obtained from the set of three-dimensional coordinate data, a distance of the n points viewed from the (n-2) th virtual plane is obtained as an evaluation height. Things.

In the method for evaluating flatness of an electrode pad on a mounting surface of a mounting board according to the present invention, the lowest value of the evaluation heights is formed by the plurality of electrode pads. The flatness of the surface to be processed is characterized.

[0015]

According to the method for evaluating the flatness of a mounting substrate of the present invention, a plurality of electrode pads formed on a mounting surface of a mounting substrate are selected so as to be distributed on the mounting surface. For the n measurement points (where n is an integer of 4 or more), the plane coordinates and the height in the three-dimensional coordinate measurement system are measured as a set, and the plane coordinates and the height of the n measurement points are measured. Is used to evaluate the flatness of the mounting surface using n sets of three-dimensional coordinate data obtained from a set of three-dimensional coordinate data. A plane obtained by using the least squares method from the n sets of three-dimensional coordinate data is obtained as a first virtual plane. Then, a plane obtained by using the least square method from the (n-1) sets of three-dimensional coordinate data excluding the point having the lowest height from the first virtual plane among these n points is defined as a second virtual plane. From the virtual plane obtained immediately before The three-dimensional coordinate data excluding the point having the lowest height is repeated until there are three sets. After obtaining the (n−2) -th virtual plane obtained by the three sets of three-dimensional coordinate data, Since the distance viewed from the (n-2) th virtual plane is obtained as the evaluation height for each measurement point, the evaluation height viewed from the virtual plane sharing the highest three electrode pads for each measurement point is mounted. Since it can be used as an index of the height on the surface, an index for flatness evaluation reflecting the actual mounting process can be obtained, and more useful flatness evaluation can be performed.

That is, when the semiconductor device is pressed against the mounting surface of the mounting substrate, first, the plane formed by the surface on the mounting surface side of the semiconductor device, that is, the plane formed by the tips of the projecting electrodes on the lower surface becomes the mounting surface of the mounting substrate. Of the plurality of electrode pads formed on the mounting surface, the semiconductor electrode is closest to the plane formed by the tips of the protruding electrodes on the lower surface of the semiconductor device, that is, at the three highest electrode pads. After supporting the device, the deformation of these protruding electrodes causes the other protruding electrodes to also contact and join the electrode pads, and finally, the height of the lowest electrode pad to which the protruding electrodes are contacted and bonded is the highest. In order to obtain the evaluation height from the virtual plane sharing the three electrode pads,
The three points that determine the virtual plane for determining the flatness of the mounting surface can be obtained as a plane sufficient to reflect the actual mounting process, and the evaluation may deviate from the actual flatness. Thus, a virtual plane reflecting the actual mounting process can be reliably obtained. As a result, it is possible to evaluate the flatness reflecting the actual mounting process and to obtain the flatness, and to judge whether or not the semiconductor device is mounted on the electrode pads on the mounting surface, and to determine whether the mounting substrate is good. The present invention provides a method for evaluating the flatness of an electrode pad on a mounting surface of a mounting substrate, which can easily and reliably determine the quality of a product obtained by mounting a semiconductor device on a mounting surface.

According to the method for evaluating flatness of an electrode pad on a mounting surface of a mounting board according to the present invention, the lowest value of the evaluation heights is formed by a plurality of electrode pads on the mounting surface. When it is determined as the flatness of the surface, the evaluation height as viewed from a virtual plane sharing the highest three electrode pads with respect to the lowest electrode pad on the mounting surface can be used as an index, and the actual mounting process can be used. Can be obtained, so that more useful flatness evaluation can be performed using a more appropriate index as the flatness of the mounting surface. As a result, using the flatness as an index, it is easy and easy to determine whether or not a semiconductor device is mounted on the electrode pad on the mounting surface and whether or not a product obtained by mounting the semiconductor device on the mounting board is good. It can be performed reliably.

In the flatness evaluation method of the present invention,
When selecting n of the electrode pads so as to be dispersedly arranged on the mounting surface, the arrangement of the selected electrode pads is concentrated near one location on the mounting surface or is arranged to be biased to one side. The actual mounting process when mounting the semiconductor device is reflected in the overall arrangement of the plurality of electrode pads without selecting an arrangement such that the semiconductor device is arranged in a straight line. The electrode pads are selected so as to be in an appropriate dispersed state so that an effective evaluation height can be obtained.

For example, the arrangement of electrode pads in a normal semiconductor element chip is arranged near the outer edge of the semiconductor element chip, and signal input / output and power supply are routed from the outer edge to the internal active element region. In addition, a ground electrode pad for ensuring grounding is provided at a position extended from the active element region to the outer side. As described above, the arrangement of the electrode pads extending to the outer side is such that the input side and the output side are arranged facing each other as a signal input / output path or arranged at a position substantially orthogonal to the active element region as a reference. The pads are arranged at positions that do not interfere with the signal input / output unit. For this reason, a preferred form for selecting n from the arrangement of the electrode pads of the semiconductor element chip or the semiconductor device is a dispersed arrangement in the vicinity of at least three sides forming the outer side of the semiconductor element chip or the semiconductor device. This is usually the case, and can be said to be preferable as the most general arrangement.

In the method for evaluating flatness of an electrode pad on a mounting surface of a mounting board according to the present invention, a set of plane coordinates and height at each measurement point is measured by non-contact measurement. Since the evaluation can be completed without changing the state of the electrode pads on the surface, the state at the time of evaluation is maintained as it is at the time of mounting, which is preferable in that the evaluation result can be reflected in the mounting process.

[0021]

Next, a method for evaluating the flatness of an electrode pad on a mounting surface of a mounting board according to the present invention will be described in detail with reference to the drawings.

EXAMPLE 1 First, an alumina ceramic substrate having a square outer shape of 0.4 mm in thickness and 10 mm on a side was used as an insulating substrate of a mounting substrate, and a 10 μm-thick W A plurality of electrode pads made of a / Ni / Au layer were provided. The mounting surface has a square shape with a side of 2 mm, and the electrode pad is formed in a square shape with a side of 80 μm so that the center coordinates are at the positions shown in Table 1, and has a schematic shape as shown in FIG. And

FIG. 1 is a plan view showing an example of a mounting substrate to which the flatness evaluation method of the present invention is applied. In FIG.
Reference numeral 3 denotes a mounting substrate, and reference numeral 4 denotes an electrode pad provided on a mounting surface of the mounting substrate 3. Reference numeral 8 denotes a continuity test electrode pad provided in a region outside the mounting surface in the peripheral portion of the mounting substrate 3, and has a structure connected to the electrode pad 4 by a lead-out line 7.

On the other hand, in a semiconductor element as a semiconductor device, the element material is GaAs having a thickness of 0.1 mm, a conductor film is formed on substantially the entire lower surface thereof, and a plurality of projecting electrodes made of gold having a diameter of 60 μm are formed. The one formed at a position corresponding to the electrode pad on the upper surface of the mounting substrate was used.

Then, the center position of each electrode pad of the mounting substrate was measured by a non-contact type shape measuring instrument with one set of plane coordinates and height, and 24 sets of three-dimensional coordinate data were extracted.

Thereafter, the semiconductor elements are aligned on the mounting substrate by a flip-chip mounting machine, and the respective projecting electrodes are brought into contact with the corresponding electrode pads, and heat and pressure are applied to the semiconductor elements to thereby form the projecting electrodes. The electrodes are bonded to the electrode pads and the semiconductor element is flip-chip mounted,
A continuity test sample was obtained.

Then, the flatness of the electrode pads on the mounting surface was evaluated using 24 sets of three-dimensional coordinate data measured for each electrode pad of the mounting substrate.

First, as an example of the flatness evaluation method of the present invention, a plane obtained by using the least squares method based on the above-mentioned 24 sets of three-dimensional coordinate data is obtained as a first virtual plane,
The second virtual plane is determined using the least squares method based on the three-dimensional coordinate data of the remaining 23 points excluding the point having the lowest height from the first virtual plane among the 24 points. The process of determining the virtual plane and removing the lowest point is repeated until the number of the three-dimensional coordinate data becomes three sets, and after determining the 22nd virtual plane obtained by the finally left three sets of data, all 24 The distance of the point measurement point as viewed from the 22nd virtual plane was determined as the evaluation height for each measurement point, and is shown in the A (final) column of technique A in Table 1. Note that each virtual plane is Z =
Each coefficient m1, m when expressed as m1X + m2Y + b
2 and b are also shown below the same column.

As a comparative example (conventional evaluation method),
Electrode pads No. 1, No. 7, and No. 13 are set among the four points located at the square vertex on the mounting surface as specific three points,
The plane sharing these three points was calculated as a virtual plane, and the height of each electrode pad as viewed from the plane was extracted, and is shown in the method B column of Table 1. Note that this virtual plane is represented by Z = m1X + m2
Each coefficient m1, m2, and b when represented as Y + b is also shown below the same column.

Another comparative example (another conventional evaluation method)
As a virtual plane, a plane obtained by using the least squares method is determined from a set of three-dimensional coordinate data of the electrode pads of all 24 points described above, and the measurement points of all 24 points are defined as heights viewed from this virtual plane. And the results are shown in the column of Method C in Table 1. The coefficients m1, m2, and b when this virtual plane is represented as Z = m1X + m2Y + b are also shown below the same column. This example corresponds to the first stage (method A1) of the evaluation method in the flatness evaluation method of the present invention.

[0031]

[Table 1]

Then, the height data of the mounting board obtained by these methods A, B and C is stored in the electrode pad No.
FIG. 2 is a diagram showing the results of extraction in the order of No. 1 to No. 24 so as to go around the mounting area. In FIG. 2, the horizontal axis represents the circumference length from No. 1 when the electrode pad No. 1 is started to No. 1 to No. 24 as a starting point (indicating the distance followed along the path when the circuit goes around. : Mm), the vertical axis represents the height (unit: μm) viewed from a virtual plane for evaluating the flatness extracted by each method, the solid line represents the result obtained by the method A, and the broken line represents the method. B indicates the result obtained by the method, and the dashed line indicates the result obtained by the method C.

As shown in FIG. 2, in the method A, the electrode pad No. 7 is lowest, in the method B, the electrode pad No. 20 is lowest, and in the method C, the electrode pad No. 21 is evaluated as the lowest electrode pad. You can see that.

On the other hand, when the continuity between each electrode pad and the protruding electrode was confirmed by using the continuity test electrode pad, it was found that a continuity defect occurred in the electrode pad No. 7.

The electrode pad having the conduction failure is the electrode pad determined to be the lowest by the method A for evaluating the flatness of the electrode pad on the mounting surface of the mounting board of the present invention, An evaluation result reflecting the actual mounting process was obtained.

Thus, according to the method for evaluating flatness of an electrode pad on a mounting surface of a mounting board according to the present invention, it is possible to obtain an evaluation height and flatness which are indicators of flatness reflecting an actual mounting process. It can be confirmed that the quality determination when mounting the semiconductor device on the electrode pads on the mounting surface and the quality determination of the product obtained by mounting the semiconductor device on the mounting board can be performed easily and reliably. Was.

Example 2 The same mounting substrate and 200 semiconductor devices as those in [Example 1] were prepared, and each mounting substrate was evaluated by the method for evaluating the flatness of the electrode pads on the mounting surface of the mounting substrate of the present invention. After evaluating the flatness, the semiconductor element is aligned with the mounting substrate by a flip chip mounting machine, and each protruding electrode is brought into contact with the corresponding electrode pad,
By applying heat and pressure to the semiconductor element, the protruding electrode was bonded to the electrode pad, and the semiconductor element was flip-chip mounted, thereby obtaining a sample for a conduction test.

A continuity test between the electrode pads and the protruding electrodes was performed using the continuity test electrode pads using each continuity test sample. As a result, it was found that continuity failure occurred in 14 samples. Do you get it.

As a distribution of flatness of each mounting substrate, a result as shown by a histogram in FIG. 3 was obtained. As a result, it was found that the 14 samples having a connection failure in the continuity test had a flatness greater than 9 μm obtained by the flatness evaluation method of the mounting board of the present invention,
It has been found that the occurrence of connection failure due to the variation in the height of the electrode pad and the evaluation index obtained by the present invention are in good agreement.

Thus, the method for evaluating flatness of an electrode pad on the mounting surface of a mounting board according to the present invention can obtain an evaluation index of flatness reflecting an actual mounting process.
A mounting surface electrode pad that can easily and reliably determine the quality of a semiconductor device mounted on the mounting surface electrode pad and the quality of a product obtained by mounting the semiconductor device on the mounting substrate. As a result, it was confirmed that the evaluation method can easily and reliably determine whether or not the semiconductor device is mounted on the mounting substrate and whether or not the product obtained by mounting the semiconductor device on the mounting board is defective.

It should be noted that the above is only an example of the embodiment of the present invention, and the present invention is not limited to the embodiment. No problem.

For example, when a set of three-dimensional coordinate data is extracted at each point, not only the center of the electrode pad is measured but also its surroundings are measured at a plurality of points, and the measured values are averaged. The result may be used as a set of three-dimensional coordinate data for the electrode pad.

Further, for example, as the shape of the mounting substrate,
When mounting a semiconductor device, if it is known that three electrode pads that can be supported are present only on a specific electrode pad and cannot be supported by other connection electrode pads, the plurality of supportable electrode pads cannot be supported. After extracting a virtual plane by applying the flatness evaluation method of the present invention only for the electrode pads,
The flatness of all the electrode pads may be evaluated based on the evaluation height viewed from the virtual plane.

[0044]

As described above, according to the method for evaluating the flatness of the electrode pads on the mounting surface of the mounting substrate according to the present invention, the mounting surface of the plurality of electrode pads formed on the mounting surface of the mounting substrate is determined. For n measurement points (where n is an integer of 4 or more) selected so as to be distributed above, 3
The plane coordinates and height in the three-dimensional coordinate measuring system are measured as a set, and the flatness of the mounting surface is evaluated using n sets of three-dimensional coordinate data obtained from the plane coordinates and the height of these n measurement points. A plane obtained from the n sets of three-dimensional coordinate data by using the least squares method as a first virtual plane, and then, of these n points, the point having the lowest height from the first virtual plane is determined. A plane obtained by using the least squares method from the (n-1) sets of the three-dimensional coordinate data that have been removed is obtained as a second virtual plane, and in the same manner as described above, the height from the virtual plane obtained immediately before is the lowest. The process is repeated until three sets of three-dimensional coordinate data excluding points are obtained. After obtaining the (n-2) th virtual plane obtained by the three sets of three-dimensional coordinate data, the (n-2) th virtual plane is obtained for the original n points. ) The distance viewed from the virtual plane is the evaluation height for each measurement point. From the virtual plane sharing the three highest electrode pads for each measurement point, it is possible to use the evaluation height as an index of the height on each mounting surface, thus reflecting the actual mounting process. An index for flatness evaluation can be obtained, and more useful flatness evaluation can be performed.

As a result, it is possible to evaluate the flatness reflecting the actual mounting process and obtain the flatness, and to judge whether or not the semiconductor device is mounted on the electrode pad on the mounting surface, The quality of a product obtained by mounting a semiconductor device on a mounting substrate can be easily and reliably determined.

According to the method for evaluating flatness of an electrode pad on a mounting surface of a mounting board according to the present invention, the lowest value of the evaluation heights is formed by a plurality of electrode pads on the mounting surface. In the case of obtaining the flatness of the surface, the height as viewed from a virtual plane sharing the highest three electrode pads with respect to the lowest electrode pad on the mounting surface can be used as an index, and the actual mounting process can be reduced. Since the reflected flatness index can be obtained, more useful flatness evaluation can be performed using a more appropriate index as the flatness of the mounting surface. As a result, using the flatness as an index, it is easy and easy to determine whether or not a semiconductor device is mounted on the electrode pad on the mounting surface and whether or not a product obtained by mounting the semiconductor device on the mounting board is good. It can be performed reliably.

As described above, according to the present invention, it is possible to obtain an index of flatness reflecting the actual mounting process on the mounting surface of the mounting substrate, and mount the semiconductor device on the electrode pads on this mounting surface. To provide a method for evaluating the flatness of an electrode pad on a mounting surface of a mounting board, which can easily and surely determine the quality of the product at the time of mounting and the quality of a product obtained by mounting a semiconductor device on the mounting board. Was completed.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a mounting board to which a flatness evaluation method of the present invention is applied.

FIG. 2 is a line showing a comparison of the evaluation results of the flatness of the electrode pads on the mounting surface of the mounting substrate obtained by the mounting substrate flatness evaluation method of the present invention and the conventional mounting substrate flatness evaluation method. FIG.

FIG. 3 is a histogram showing a distribution of flatness of a mounting board obtained by a method for evaluating flatness of a mounting board of the present invention.

FIGS. 4A and 4B are side views for explaining a step of flip-chip mounting a semiconductor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor device 2 ... Protruding electrode 3 ... Mounting substrate 4 ... Electrode pad

Claims (2)

[Claims] 1. A mounting substrate having a plurality of electrode pads on a mounting surface on which a semiconductor device is mounted and to which protruding electrodes of the semiconductor device are connected, the plurality of electrode pads being distributed on the mounting surface of the electrode pads. Selected n (however,
(n is an integer of 4 or more) is measured as a set of the plane coordinates and the height in the three-dimensional coordinate measurement system for the measurement point set to (4) or more, and is obtained from the n sets of three-dimensional coordinate data obtained using the least squares method. Is obtained as a first virtual plane, and then the least squares method is used from (n-1) sets of three-dimensional coordinate data excluding the point having the lowest height from the first virtual plane among the n points. The obtained plane is obtained as a second virtual plane, and the same procedure is sequentially repeated until three sets of three-dimensional coordinate data excluding the point having the lowest height from the immediately preceding virtual plane are obtained. After obtaining the (n-2) th virtual plane obtained by the three-dimensional coordinate data of the above, the distance from the (n-2) th virtual plane to the n point is obtained as an evaluation height. Of the electrode pads on the mounting surface of the Gender evaluation method. 2. The flatness evaluation method according to claim 1, wherein a value of a lowest height among the evaluation heights is a flatness of a surface formed by the plurality of electrode pads. A method for evaluating flatness of an electrode pad on a mounting surface of a mounting substrate.