JP4995041B2 - Printed solder inspection method and printed solder inspection apparatus - Google Patents

Description

  The present invention relates to a printed solder inspection method and apparatus for measuring and inspecting a solder formation state when cream-like solder is printed on a printed board for surface mounting electronic components and the like. In particular, a printed circuit board is a portion where solder is to be printed (hereinafter referred to as a “solder location”), a circuit pattern (pad) is revealed, and a pad portion on which a component can be attached, and a circuit There is a resist part (a part where solder is not printed) on which a semi-transparent resist is applied on the pattern. However, according to the present invention, the height of the actually printed solder is the height from the pad surface (circuit pattern surface). It relates to the technology that can be measured as.

  Conventionally, as a printed solder inspection apparatus, the surface of a printed board (hereinafter, a printed board on which solder is printed is simply referred to as “substrate”, and a printed board on which solder is not printed is referred to as “unprinted board”). A sensor that irradiates with a laser beam or the like and receives reflected light from the surface of the substrate, and a measurement value obtained as a result of measurement (triangulation) by the sensor, for example, a printed solder spot on the substrate Judgment based on measurement values of displacement (including height) or luminance (including the amount of light reflected from the substrate and the amount of received light (intensity of light)) with reference data serving as a criterion for determination (Patent Documents 1 and 2).

  In Patent Document 1, for example, an average height of a peripheral portion of a solder portion as shown in FIG. 8 is obtained, and the solder height is measured based on the average height of the resist 1a portion. In the technique of Patent Document 1, in obtaining the average height of the resist 1a portion around the solder location, there is a gap between the resist 1a portion and the solder location, and therefore the average height of the resist 1a portion excluding that portion. This is the basis for this.

  By the way, recently, from the field of printing solder, it is desired to know the amount of solder printed accurately. For this reason, the solder actually printed on the surface of the pad 1c, which is the place where the solder is printed. There has been a growing demand for measuring height. Then, the technique of Patent Document 1 cannot be applied as it is.

Therefore, as shown in Patent Document 2, from the surface of the pad 1c, the height of each portion measured in advance on an unprinted substrate and the height of each portion obtained by measuring the substrate on which the solder 1b is actually printed are obtained. The technology of measuring the solder height is provided.
And in patent document 2, it calculates | requires as follows mediating the resist 1a surface.
Solder height = (solder height from resist 1a surface) + (resist 1a surface height from pad 1c surface) = solder height from pad 1c surface Therefore, in this case, the height of resist 1a surface is measured. However, since it is finally erased in the calculation, measurement can be performed while suppressing the influence of the absolute height of the resist 1a surface.

JP 2002-228597 A Japanese Patent Application No. 2006-159702

  By the way, depending on the application method, the resist 1a surface tends not to be applied uniformly, for example, at the end of the boundary with the soldered portion as shown in FIG. FIG. 9A shows a case where the resist 1a is applied from the right to the left of the paper surface, where the right resist 1a end is thin and the left resist 1a end is thick. FIG. 9C shows a case where an ideal application is performed. In FIG. 9B, the average value (the dotted line in FIG. 9B) of the thickness (height) around the edge of the resist 1a is the right side and the left side of the edge of the resist 1a surface sandwiching the solder location. It can be seen that the values are different.

  It is sufficient that the application state of the resist 1a on each substrate is constant and the shape as shown in FIG. 9C can be formed and maintained. However, if this is likely to vary depending on the substrate, an error is likely to occur in Patent Document 2. In the case of Patent Document 2, the “resist 1a height from the pad 1c surface” of the above formula is measured and stored in advance on an unprinted substrate, and the stored value is measured for each solder location. Therefore, “the height of the resist 1a from the pad 1c surface” must be constant for each substrate. In other words, if it is not stable as shown in FIG. 9B, if the height of the edge of the resist 1a varies from one substrate to another, it may cause an error.

  On the other hand, the inventor investigated and examined whether the thickness of the translucent resist 1a could be obtained. First, as shown in FIG. 7A, light is incident obliquely on the surface of the resist 1a, the specular reflection light is taken in, and a position relative to a certain reference position (a reference position even when the solder is printed) is preferable. ) Measure the displacement L2. Next, as shown in FIG. 7B, light is incident on the resist 1a surface from the vertical direction, and the scattered reflected light scattered symmetrically with respect to the incident optical axis is taken in, and the displacement L1 with respect to a certain reference position is measured. . At this time, the scattered reflected light includes both light that passes through the resist 1a and is scattered and reflected on the circuit pattern surface (pad surface) such as a copper foil below the resist 1a, and light that is scattered and reflected on the surface of the resist 1a. There is a possibility that When these measured values and the difference δL = L2−L1 are plotted, FIG. 7C is obtained. In the following description, “position” and “reference position” refer to the position in the height direction on the substrate.

  Therefore, it was found that if the correlation between the difference δL and the like and the thickness of the resist 1a can be obtained stably even if the displacement L2 and the displacement L1 fluctuate, the thickness of the resist 1a can be obtained corresponding to the difference δL. In fact, if the displacement L2 is a continuous and smooth shape, data having a correlation between the difference δL and the thickness of the resist 1a was obtained. This is schematically shown in FIG. If the correlation is obtained as described above, a correction value Ls (corresponding to the thickness of the resist 1a) for obtaining the position of the pad surface can be obtained empirically from the relationship between the difference δL and the thickness of the resist 1a. This is shown in FIG. FIG. 6B shows the estimated position of the pad surface 1c (circuit pattern surface) = L2-Ls using the correction value Ls obtained with reference to FIG. 6A based on δL obtained by measurement. It is a figure which shows calculating | requiring. Therefore, since the position of the pad surface under the resist 1a can be estimated, the height of the solder from the pad surface can be measured.

  The object of the present invention is to measure the displacement of the resist surface when the circuit pattern of the pad is below the resist surface with each of the regular reflection light and the irregular reflection light, and based on the correlation between the two, the position of the pad surface under the resist It is intended to provide a printed solder inspection apparatus that estimates the solder height (displacement) from the position.

  In order to achieve the above object, the invention described in claim 1 is directed to irradiating light perpendicularly to a measurement point on the surface of a printed board and receiving the scattered light from the measurement point to measure the first displacement. The first sensing means (OS1, D1, D2) and the same measurement point are irradiated at an angle oblique to the vertical by a predetermined angle, and the reflected light specularly reflected at the measurement point is measured to determine the second displacement. Preparing a displacement sensor (2) including second sensing means (OS2, D3) for measuring, and using the displacement sensor as the resist surface of the printed board, the second displacement and the second displacement. The initial stage of measuring the displacement of 1 and storing the function value representing the relationship between the difference and the thickness of the resist in the memory, and receiving the measurement printed board on which the solder is printed on the surface pad surface The resist surface of the printed board to be measured and the pattern A measurement step for obtaining the first displacement and the second displacement by the displacement sensor using the solder surface on the soldering surface as the measurement point, the first displacement obtained on the resist surface in the measurement step, and the A reference position calculating step of obtaining a corresponding function value by referring to the memory based on a difference from a second displacement, and subtracting the function value from the second displacement to obtain a position of the pad surface; A displacement calculating step of obtaining a displacement of the solder surface as a displacement from the position of the pad surface by the first displacement or the second displacement in the solder surface measured in the measuring step.

  The invention according to claim 2 irradiates light perpendicularly to a measurement point on the surface of the printed board to be measured having a pad surface on which solder is printed and a resist surface, and receives scattered light from the measurement point. First sensing means (OS1, D1, D2) and second sensing means (OS2, OS2) that receives the same measurement point at an oblique angle with respect to the vertical and receives reflected light that is regularly reflected at the measurement point D3), a first displacement based on scattered light from the output of the first sensing means, and a second displacement based on specularly reflected light from the output of the second sensing means. A printed circuit board inspection apparatus comprising a data processing unit (3) for calculating and a measurement unit (7) for obtaining displacement of the solder surface by the first displacement or the second displacement, Second displacement and first on the resist surface A memory (5) for storing a function value representing a relationship between the difference between the displacement and the thickness of the resist, and at the time of inspection, the first sensor by the displacement sensor with the resist surface of the measured printed board as the measurement point. A basic measurement unit (6) for obtaining a displacement and the second displacement, and a corresponding function with reference to the memory based on a difference between the first displacement and the second displacement obtained on the resist surface A reference position calculation unit (6a) for obtaining a value and subtracting the function value from the second displacement to obtain a position of the pad surface, wherein the measurement unit is soldered from the position of the resist surface. By correcting the displacement of the surface with the function value, the displacement of the solder surface is obtained as the displacement from the position of the pad surface.

  The invention according to claim 3 is the same measurement as the first sensing means (OS1, D1, D2) that irradiates light perpendicularly to the measurement point on the surface of the printed board and receives scattered light from the measurement point. Displacement sensor (2) including second sensing means (OS2, D3) that receives reflected light that is reflected at a predetermined angle with respect to the vertical angle and is specularly reflected at the measurement point, and the first sensing A data processing unit (3) for calculating a first displacement based on scattered light from the output of the means and a second displacement based on specularly reflected light from the output of the second sensing means; A memory (5) for storing a function value representing a relationship between the difference between the first displacement and the thickness of the resist; and a measured printed board on which solder is printed on the pad surface of the surface. The change is made with the resist surface of the plate as the measurement point. The basic measurement unit (6) for obtaining the first displacement and the second displacement by a sensor, and the memory based on a difference between the first displacement and the second displacement obtained on the resist surface. A reference position calculation unit (6a) for obtaining a corresponding function value by reference and subtracting the function value from the second displacement to obtain the position of the pad surface; and the solder surface of the measured printed board And a measurement unit (7) for obtaining the first displacement or the second displacement by the displacement sensor as the measurement point and obtaining the displacement of the solder surface as a displacement from the position of the pad surface.

  The invention according to claim 4 is the invention according to claim 2 or 3, wherein the first sensing means includes a first light source (OS1) for irradiating a measurement point of the printed board from a vertical direction, A first light receiving means (D1) disposed on a first scattered light path formed at a first angle θ1 with respect to the first optical axis of the first light source, and the first optical axis; And a second light receiving means (D2) disposed on a second scattered light path formed at a second angle θ2 on the opposite side of the first scattered light path, wherein the first displacement is It is obtained based on the sum of the output of the first light receiving means and the output of the second light receiving means, and the second sensing means has the angle θ3 inclined with respect to the first optical axis. A second light source (OS2) that irradiates the measurement point and a third angle 2θ3 with respect to the second optical axis of the second light source at the measurement point A third light receiving means and (D3) which is arranged in the positive reflected light path that is, the second displacement, and the structure obtained from the output of the light receiving means of the third.

  According to a fifth aspect of the present invention, in the displacement sensor according to the fourth aspect, each of the first light receiving means, the second light receiving means, and the third light receiving means has a predetermined length. A position detector that detects light displacement information according to a light receiving position in the predetermined length direction, the first optical axis, the optical axis of the second light source, and the first light source. In the plane including the scattered light path, the second scattered light path, and the regular reflection light path, the predetermined length direction is arranged along the plane, and the first angle θ1, the second angle θ2, and The third angle 2θ3 is configured to be the same, and the angle (α1) formed by the first light receiving unit with the first scattered light path, and the angle formed by the second light receiving unit with the second scattered light path. The angle (α3) formed by (α2) and the third light receiving means with the regular reflection optical path is the same. So as configured.

The invention according to claim 1, 2 or 3 includes displacement measurement by regular reflection light in triangulation on the resist surface and displacement measurement by scattered reflected light in mutually opposite directions when irradiated from the vertical on the resist surface. The position of the pad surface is obtained from the measured values, the height (displacement) of the solder surface is measured using specular reflection light or scattered reflection light, and the solder surface from the pad surface on which the solder is printed is measured. The height can be determined.
The invention according to claim 5 can measure the light receiving sensitivities of specularly reflected light and two scattered reflected light in the same manner.

  A printed solder inspection apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a functional configuration of a displacement sensor and a measurement unit in the first embodiment, and is a view of a form in which a displacement sensor and a measurement object are relatively scanned and inspected. FIG. 2 is a diagram illustrating a functional configuration of the inspection unit in the embodiment. FIG. 3 is a diagram showing an arrangement of functional elements constituting the displacement sensor of FIG. FIG. 4 is a diagram illustrating the positional relationship between the light receiving means and explaining the sensitivity of each light receiving means. FIG. 5 is a diagram showing an embodiment of a second embodiment in which optical scanning is performed by a light source in a displacement sensor.

[Configuration of First Embodiment]
A functional configuration of a displacement measuring unit 100 that performs displacement measurement using the displacement sensor 2 will be described with reference to FIG.

  1 and 3, the displacement sensor 2 includes a first light source OS1 and a first light receiving unit on a single plate-like substrate or a base on a flat plate (hereinafter referred to as “base”, not shown). The means D1, the second light receiving means D2, the second light source OS2, and the third light receiving means D3 are formed so as to integrally form one housing with their positional relationships fixed. Yes. The first light source OS1 irradiates the measurement point (target position) on the surface of the substrate 1 with light (hereinafter referred to as “light” although it is a light beam) along the first optical axis from the vertical direction. is there. The first light receiving means D1 is disposed on a first scattered light path formed at a measurement point at a first angle θ1 with respect to the first optical axis. The second light receiving means D2 is arranged on the second scattered light path formed at the second angle θ2 on the opposite side of the first scattered light path with respect to the first optical axis (the above is the “first light beam”). 1 sensing means "). The light source OS2 irradiates the measurement point with the light of the second optical axis that forms an oblique angle θ3 with respect to the first optical axis. The third light receiving means D3 is disposed on a regular reflection optical path formed at a third angle 2θ3 with respect to the second optical axis of the second light source at the measurement point (the above is the “first 2 sensing means ").

  Each of the first light receiving means D1, the second light receiving means D2, and the third light receiving means D3 has a light receiving surface with a predetermined length, and the optical displacement information according to the light receiving position in the predetermined length direction. A position detector (PSD: Position Sensitive Detector) is used. In the PSD, light detection elements are arranged in the length direction, and output A and output B, which are electric quantities corresponding to the position, are output from each end as information indicating positions from both ends in the length direction. Then, the displacement information is indicated by (A−B) / (A + B). In addition to the output of the displacement information, the first light receiving means D1, the second light receiving means D2, and the third light receiving means D3 measure the amount of reflected light from the measurement point and output the light amount information. The PSD is an element that changes the light receiving position according to the displacement of the measurement point and outputs an electric quantity corresponding to the light receiving position, that is, an element that outputs the displacement expressed in the electric quantity. Instead of the PSD, the light receiving position may be directly output as the displacement position by a photodiode array, a CCD, or the like.

  The displacement sensor 2 at the position shown in FIG. 1 moves the entire sensor with respect to the substrate 1 while maintaining the positional relationship between the elements in the direction orthogonal to the arrangement direction of the optical elements in FIG. Thus, by scanning, the surface displacement of the substrate 1 can be measured over a wide range.

  In FIG. 1, the scanning mechanism 4 has a driving source such as a motor and a driving mechanism such as a belt, and scans the substrate 1 or the displacement sensor 2 or both by relatively moving them. In FIG. 1, the displacement sensor 2 measures displacement while performing main scanning in a direction perpendicular to the arrangement direction in which the respective elements such as the first light receiving means D1 are arranged (depth direction perpendicular to the paper surface of FIG. 1). When the main scanning is completed, the displacement is measured by moving (sub-scanning) in the arrangement direction (direction parallel to the paper surface of FIG. 1), changing the position, and performing the main scanning. By repeating this operation, the displacement of the substrate 1 in the desired range is measured. Note that the scanning direction is an example, and other directions may be used.

  The correction memory 5 stores a correction value for obtaining the thickness of the resist 1a in advance before inspecting many substrates 1. As disclosed in the “problem to be solved” using the displacement sensor 2, the correction value is obtained when the operator places the first surface of the resist 1 a on the representative substrate 1 to be inspected. The scattering reflection displacement measurement is performed by the sensing means, and the displacement of the resist 1a surface is measured by the regular reflection displacement measurement by the second sensing means, and the relationship between the difference δL between the measured values and the actual thickness of the resist 1a A function value Ls shown is obtained. Since the function value Ls is used for correction, the function value Ls will be described below as the correction value Ls. The acquired correction value Ls is acquired and stored in the correction memory 5 so that the corresponding correction value Ls can be read from the difference δL. This can be done in the present embodiment using the basic measurement unit 6 described later, or δL and the correction value Ls may be acquired externally and stored in the correction memory 5. However, the former is more reliable because it can be obtained by using the same displacement sensor 2 as the acquisition of the correction value Ls and the measurement for inspection.

  In response to an instruction from a panel or the like (not shown), for example, the control unit 12 receives an instruction for a desired measurement range of a printed board on which solder is printed, and sends a scanning instruction for the desired range to the scanning mechanism 4 as described above. To scan. In scanning, when the first light source OS1 and the second light source OS2 use light sources having the same wavelength, the first light source OS1 and the first light source OS1 are scanned at the same scanning position (measurement point) on the substrate (object to be measured) 1. The second light source OS2 is alternately switched. When light sources having different wavelengths are used, it is not always necessary to switch them, and a configuration in which they are simultaneously output may be used.

  In addition, the control unit 12 causes the basic measurement unit 6 to perform basic measurement to obtain the thickness of the resist 1a and estimate the position of the pad 1c. Further, the height of the surface of the solder 1b is measured from the position of the pad 1c by the measurement unit 7. Details will be described later.

  The data processing unit 3 includes an adder 3a, an adder 3b, and a calculation unit 3c, and calculates the displacement (data) at the measurement point based on the output from each light receiving means. The adder 3a receives the output A1 of the first light receiving means D1 and the output A2 of the second light receiving means D2, adds them, and outputs Ax = A1 + A2. The adder 3b receives the output B1 of the first light receiving means D1 and the output B2 of the second light receiving means D2, adds them, and outputs Bx = B1 + B2. The computing unit 3c obtains an output L1 = (Ax−Bx) / (Ax + Bx), which is displacement information due to irregular reflection, based on them. Or / and the calculation unit 3c receives the output from the third light receiving means D3 and obtains the output L2 = (A3−B3) / (A3 + B3), which is displacement information by regular reflection.

  At this time, the output L1 and L2 of the calculating part 3c differ in the aspect utilized according to the instruction | indication from the basic measurement part 6 or the measurement part 7, as demonstrated below.

  When measuring the thickness of the resist 1a, that is, when estimating the position of the pad 1c surface, the control unit 12 causes the basic measurement unit 6 to perform basic measurement, and when measuring the height of the solder 1b. Let the measurement part 7 perform. Details will be described in (1) and (2) below. Whether the measurement is on the solder 1b surface or the measurement on the resist 1a surface is different in the amount of reflected light between the resist 1a surface and the solder 1b surface. When it is less, it can be determined as the solder 1b surface and the measurement can be switched. In addition, since the displacement sensor position is scanned based on the design in advance, it is possible to determine which measurement is performed from the position information based on the design information. The switch S1 is switched to the basic measurement unit 6 side or the measurement unit 7 side according to the determination.

(1) Basic measurement The basic measurement unit 6 receives the output L2 that is a measurement value based on regular reflection from the calculation unit 3c when the measurement point is the resist 1a and the measurement value obtained by scattered reflected light. In response to the output L1 _R (hereinafter, L1 and L2 on the resist 1a surface are represented by L1 _{R and} L2 _R ), a difference δL between them is obtained. Then, the correction memory 5 is accessed and FIG. ), A correction value Ls corresponding to δL is obtained. That is, a value corresponding to the thickness of the resist 1a is obtained. Then, the correction value Ls is sent to the measurement unit 7.

(2) Measurement unit 7, the resist displacement from 1a surface to solder 1b surface _(height) L1 H, L2 _H (hereinafter. Indicating the L1, L2 in the solder 1b face in _L1 H, L2 _H) taking measurement. At that time, light quantity information is received from each of the first light receiving means D1, the second light receiving means D2, and the third light receiving means D3, and the scattering reflection displacement of the output L1 _H and the output L2 _H from the calculation unit 3c. Displacement information (output L1 _H ) measured by the displacement measurement system with the larger light quantity by comparing the light quantity by the measurement system (OS1-D1, D2 system) and the light quantity by the specular reflection displacement measurement system (OS2-D3 system). selectively receives either) of the output L2 _H. Then, the measuring unit 7 corrects the received displacement information with the correction value Ls received from the basic measuring unit 6 and uses the height (displacement) information L of the solder 1b surface from the pad 1c surface as L = L1 _H + Ls. Alternatively, L = L2 _H + Ls is output to the image processing unit 8 in FIG.
The above (1) basic measurement (2) measurement is based on the same position (height), but the measurement of (2) is subordinate to the correction value Ls obtained by the basic measurement of (1). The height (displacement) information L can be obtained directly by measuring with reference to the position of.

Note that the larger output L1 _H or output L2 _H of the light amount by the scattering reflection displacement measurement system and the light amount by the regular reflection displacement measurement system is selected, for example, the shape of the convex solder 1b on the substrate 1 In the case of the second light source OS2, the side wall on the side where the optical axis hits may be measured with the oblique second optical axis of the second light source OS2, but it is specularly reflected from the opposite side wall. There is a possibility that light cannot be received. In that case, displacement information based on the outputs of the first and second light receiving means D1 and D2 can be used. That is, it is for obtaining more reliable displacement information by using the displacement information with the higher light quantity. When the shape on the substrate 1 is a smooth plane, measurement with a regular reflection displacement measurement system is sufficient.

  Furthermore, as described above, the order of (1) basic measurement and (2) measurement has been described, but the order of measurement is not necessarily limited thereto. For example, the resist 1a surface and the solder 1b surface are scanned without distinction, and outputs L1 and L2 are obtained and stored for each scanning position, and then the arithmetic processing shown in (1) above is performed to obtain only the correction value Ls. Ask for. Next, correction may be made by the arithmetic processing shown in (2) above to obtain the solder height from the pad 1c surface.

  FIG. 2 mainly shows a functional configuration of the inspection unit 200. In FIG. 2, the image processing unit 8 receives the layout information (arrangement drawing) of the substrate 1 from the control unit 12 and the position information when scanning and measuring, and receives the height (in the position information) from the measurement unit 7. In response to the displacement (L), a three-dimensional image representing the quantitative shape of the solder 1b is formed on the layout in accordance with the displacement, and is reproduced and output as an image.

  For example, the image processing unit 8 measures an area (measurement point collection area: for example, on a printed circuit board) measured from the output L of the measurement unit 7 and the measurement points (coordinates of measurement points) of the substrate 1 from the control unit 12. Image data representing the area (for example, the area on which the solder cream is printed) and the volume (for example, the amount of solder) in the printed cream solder 1b surface) is generated. The comparison unit 9 receives a design value or the like in the area from the control unit 12 as a reference (area or volume), and calculates and outputs a difference between the image data and the reference. The difference between the displacement (height: for example, the height of the solder 1b) measured at the measurement point and the reference (in this case, for example, the design height at the measurement point) without conversion into image data. May be output. In the above description, the example of the solder area and volume has been described. However, it is also possible to determine misalignment of the solder.

  The determination unit 10 receives the allowable value corresponding to the reference from the control unit 12 and compares it with the output from the comparison unit 9. If the output of the comparison unit 9 is within the allowable value, the determination unit 10 passes, and if the output is outside the allowable value. If it is defective, it is determined as bad.

  The display unit 11 displays the determination result of the determination unit 10. In addition, layout information (for example, a layout diagram of solder locations on a printed circuit board) is received from the control unit 12 and displayed so that it is possible to identify at which position in the layout the solder 1b is defective (or not) and passed. May be. Further, separately or in combination, an image based on the image data generated by the image processing unit 8 can be displayed so that it is possible to identify which part is in a defective soldering state and is acceptable.

  When the surface shape of the object to be measured is inspected using the displacement sensor 2 described above, it is possible to inspect whether or not it is acceptable, including not only the apex and the flat portion but also the shape of the inclined portion.

[Other Embodiments of Displacement Sensor]
Next, another embodiment of the displacement sensor will be described.

  In FIG. 3, the first light source OS <b> 1 is, for example, a laser and irradiates light in a direction perpendicular to the surface of the substrate 1. That is, the first optical axis is perpendicular to the surface of the DUT 1. The second light source OS2 is, for example, a laser and emits light so as to cross the first optical axis at an angle θ3 from the right direction in FIG. 1 (or from the left). This crossing position is a measurement point of the substrate 1 to be measured. Although not shown, the light from each light source is condensed on each of the first irradiation light path from the first light source OS1 to the measurement point and the second irradiation light path from the second light source OS2 to the measurement point. A collimator lens that converts the light into parallel light, and a condensing lens that condenses the parallel light on the measurement point (that is, in this case, the measurement point is the first light source OS1 and the second light source described later). It is also the position where the light from each of OS2 is collected.) Further, when the first light source OS1 and the second light source OS2 have the same wavelength, they may be light extracted from the same light source.

  In FIG. 3, the displacement measurement system by irregular reflection using the first light source OS1, the first light receiving means D1, and the second light receiving means D2 is effective when the surface of the substrate 1 has an inclination. The displacement measurement system by regular reflection using the light source OS2 and the third light receiving means D3 is effective when the surface of the substrate 1 is flat. In FIG. 3, the angle θ3 is smaller than the angle θ1 or the angle θ2, but may be larger than the angle θ1 or the angle θ2.

  In order to avoid mutual interference between specularly reflected light and scattered reflected light, the displacement measurement operation of the irregular reflection displacement measurement system using the first light source OS1, the first light receiving means D1, and the second light receiving means D2, and the second light source The displacement measurement operation by the regular reflection displacement measurement system using the OS2 and the third light receiving means D3 is performed simultaneously at different wavelengths or alternately by time sharing at the same wavelength. In the case of using different wavelengths, an optical filter that inserts wavelengths received by each of the first light receiving means D1, the second light receiving means D2, and the third light receiving means D3 and blocks other wavelengths is inserted. There is a need.

  In FIG. 3, the first irregular reflection optical path between the first light receiving means D1 and the measurement point, the second irregular reflection optical path between the second light reception means D2 and the measurement point, and the third light reception means. In each of the regular reflection optical paths between D3 and the measurement point, a collimator lens that collects each reflected light from the measurement point and converts it into parallel light, and further collects the parallel light on the measurement point to form an image. Condensing functional elements K1, K2, and K3 including a condensing lens to be provided. Here, the expression “condensing functional element” is used, but it is basically a function that condenses each reflected light (beam) and forms an image on each light receiving means. This is an expression for representing all of them because it can be achieved with a lens or a plurality of lenses. As shown in FIG. 3, the distances to the positions where the reflected light is converted into parallel light around the optical axis where each of the condensing functional elements K1, K2, and K3 is arranged are L1n, L2n, and L3n. L1m, L2m, and L3m are distances until the light receiving means collects light. The distance (the length of the condensing functional element) maintained by the condensing functional elements K1, K2, and K3 as parallel light is used to determine the position of each light receiving element with respect to the measurement point.

  Each of the first light receiving means D1, the second light receiving means D2, and the third light receiving means D3 has a light receiving surface having a predetermined length as described above, and corresponds to the light receiving position in the predetermined length direction. A position detector (PSD) that detects optical displacement information is used. Therefore, an angle α1 formed by the first light receiving unit D1 with the first scattered light path, an angle α2 formed by the second light receiving unit with the second scattered light path, and an angle α3 formed by the third light receiving unit with the specularly reflected light path, Set to These angles are set for sensitivity adjustment.

In the present embodiment, the angle α1 formed by the first light receiving unit D1 with the first scattered light path is tan ⁻¹ (L1n / L1m × tan θ1), and the angle α2 formed by the second light receiving unit D2 with the second scattered light path. Tan ⁻¹ (L2n / L2m × tan θ2) and the angle α3 formed by the third light receiving means D3 with the regular reflection optical path is tan ⁻¹ (L3n / L3m × tan2θ3). Can be measured while reducing the difference in sensitivity in the length direction of the light receiving means (direction in which the sensing elements are arranged).

  These underlying principles are called Scheimpflug Principles, and when an image is projected onto a subject surface with a lens, each of the three surfaces of the image surface, the lens surface and the subject surface is extended. If the lines meet at the same point, the entire surface of the image is said to be in focus. In the present embodiment, as shown in FIG. 2, the sensitivity of the three light receiving means is appropriately adjusted using this condition. In FIG. 4, a range R indicates a displacement range in which the DUT 1 can be measured, and indicates a surface in the length direction of the light receiving means D (representing each of the light receiving means D1, D2, and D3). An extension line of the range R (in this case, the same as the optical axis from the light source), an extension line of the surface of the condensing function element K (representing each condensing function element K1, K2, K3), and light receiving means Displacement can be measured with appropriate sensitivity in the length direction of the light receiving means (in other words, in the entire range R) by arranging and arranging so that the extended line of the surface of D intersects at one point. .

  In the above formula, the distance ratios L1n / L1m, L2n / L2m, and L3n / L3m have the same value, and the first angle θ1, the second angle θ2, and the third angle 2θ3 have the same value (θ). Therefore, the angle α1, the angle α2, and the angle α3 with respect to the range R also have the same value (α), and the difference in sensitivity between the light receiving means can be reduced for measurement.

  In the above formula, the first angle θ1, the second angle θ2, and the third angle 2θ3 are the same regardless of whether the distance ratios L1n / L1m, L2n / L2m, and L3n / L3m have the same value. If the angle α1, the angle α2, and the angle α3 are also set to the same value (α) by setting the value (θ), the in-focus portion and the out-of-focus portion are generated inside the light-receiving device, but the sensitivity variation between the light-receiving devices is suppressed. be able to. In addition, the distance and angle in the present invention are described by the value of the approximate center in the measurement range.

  As described above, the displacement sensor 2 uses the irregular reflection displacement measurement system that uses two symmetrical symmetrical reflections, and is divided into the irregular reflection displacement measurement system and the regular reflection displacement measurement system. In addition, since the first angle θ1, the second angle θ2, and the third angle 2θ3 have the same value (θ), each displacement measurement can have the same sensitivity. Regardless of the reflectance of the measurement object 1, it is possible to measure the shaded part of specular reflection without sensitivity correction, reducing the difference in displacement measurement between the diffuse reflection displacement measurement system and the regular reflection displacement measurement system, and measuring with high accuracy. Can do.

[Second Embodiment]
A displacement sensor 2a in the second embodiment is shown in FIG. FIG. 5A is a view of the displacement sensor 2a viewed from the top, and FIG. 5B is a view of the displacement sensor 2a viewed from the side, both of which show the optical paths between the elements. FIG.5 (c) is a figure which shows the optical path seen from the arrow A and arrow B of FIG.5 (b).

  In the second embodiment, the main difference in configuration from the first embodiment in FIG. 1 is that in the first embodiment, the entire displacement sensor 2 is mechanically moved to perform main scanning. However, in the displacement sensor 2a in the second embodiment, the main scanning is performed using the rotation of the polygon mirror PM. Similar to the first embodiment, the sub-scan is performed by mechanically moving either the displacement sensor 2a or the substrate 1 or both. The scanning directions of main scanning and sub-scanning are the same as in the first embodiment (may be different). Therefore, the scanning mechanism 4 in FIG. 1 is in charge of only the sub-scanning in the second embodiment. Similarly, for the main scanning, the control unit 12 in FIG. 1 directly controls the polygon mirror PM of the displacement sensor 2a to perform the main scanning. Other configurations are the same as those in FIG. 1 except as described below.

  The optical configuration of the displacement sensor 2a will be described with reference to FIG. The first light receiving means D1, the second light receiving means D2, and the third light receiving means D3 have the same configuration and the same functions and operations as those described in the first embodiment, but with respect to the main scanning direction. Thus, the sensor can be sensed with a width corresponding to the distance of the main scanning (the vertical direction in FIG. 5A and the depth direction in FIG. 5B). The combination of the light receiving lens K1a and the imaging lens K1b, the combination of the light receiving lens K2a and the imaging lens K2b, and the combination of the light receiving lens K3a and the imaging lens K3b are each a condensing functional element K1 in the first embodiment. , K2, and K3, and the functional operations are also the same. That is, the light (reflected light) collected by the light receiving lenses K1a, K2a, and K3a is converted into parallel light, and the imaging lenses K1b, K2b, and K3b that receive the parallel light form images on the light receiving means D1, D2, and D3. Similarly to each of the light receiving means D1, D2, and D3, the width is the main scanning distance with respect to the main scanning direction (the vertical direction in FIG. 5A and the depth direction in FIG. 5B). It is configured to receive light and form an image.

  5A and 5B, the laser OSC1a, the half mirror OSC1b, the mirror OSC1c, the mirror OSC1d, the polygon mirror PM, the mirror OSC1e, the fθ lens OSC1f, and the mirror OSC1g as a whole are the first light source of the first embodiment. Corresponds to OSC1. However, it differs in that the main scanning is performed by the polygon mirror PM. The entire laser OSC1a, half mirror OSC1b, mirror OSC2a, mirror OSC1c, PM, mirror OSC2b, and fθ lens OSC2c correspond to the second light source OSC2 of the first embodiment. FIG.5 (c) is a figure seen from the arrow A and B of FIG.5 (b), and is a figure which shows a mode that an optical path direction is converted.

  Next, the optical path and main scanning will be mainly described. The light output from the laser OSC1a is partially branched by the half mirror OSC1b, reflected by the mirror OSC1c and the mirror OSC1d, and input to the polygon mirror PM. The light input to the polygon mirror PM is emitted to the mirror OSC1e at an angle corresponding to the rotation by the rotation of the polygon mirror PM (right rotation in FIG. 5). The mirror OSC1e turns back along the optical path specularly reflected with respect to the angle when the received light is received, and sends it to the fθ lens OSC1f. As shown in FIG. 5 (c), the fθ lens OSC1f is an optical path in which light incident at an angle according to the rotation of the polygon mirror PM is arranged in parallel in the scanning direction at a certain interval with an optical path having an angle that expands according to the rotation. And sent to the mirror OSC1g through the optical path. The mirror OSC1g irradiates the measurement point with the received light from the vertical direction. At this time, in FIG. 5B, the measurement point is main-scanned in the depth direction from the front of the paper according to the rotation of the polygon mirror PM. The first light receiving means D1 and the second light receiving means D2 receive the scattered light from the measurement point for the irradiation from the mirror OSC1g and measure the displacement.

  On the other hand, of the light output from the laser OSC1a, the remaining light branched by the half mirror OSC1b is reflected by the mirror OSC2a and input to the polygon mirror PM. The light input to the polygon mirror PM is emitted to the fθ lens OSC2c at an angle corresponding to the rotation by the rotation of the polygon mirror PM. Like the fθ lens OSC1f, the fθ lens OSC2c passes light incident at an angle corresponding to the rotation of the polygon mirror PM through an optical path arranged in parallel in the scanning direction at a constant interval, as shown in FIG. Further, the measurement point is irradiated from obliquely above at a certain angle θ3 with respect to the vertical. At this time, in FIG. 5B, according to the rotation of the polygon mirror PM, the measurement point is main-scanned from the depth of the paper to the front (opposite to the scanning by the vertical light from the mirror OSC1g). ). The third light receiving means D3 receives the specularly reflected light from the measurement point for the irradiation from the fθ lens OSC2c and measures the displacement.

  As described above, the output light from the mirror OSC1g plays the role of the light source of the scattering reflection measurement system (first sensing means), and the output light from the fθ lens OSC2c is the regular reflection measurement system (second It plays the role of the light source of the sensing means. However, although both light beams are irradiated at the same measurement point, the scanning directions are reversed because the same polygon mirror PM is used. In other words, the scattering reflection measurement system and the regular reflection measurement system have different scanning times and directions at the same measurement point in the same main scanning. However, this differs only in the order of measurement, and there is no change in that the same measurement point is measured by both. Also, the time difference when scanning is short and has little effect. Further, the irradiation position error due to the different scanning directions can be suppressed within an allowable range.

  In the second embodiment, when the scattering reflection measurement system and the specular reflection measurement system are performed simultaneously, the laser OSC1a having the same wavelength is used, so that crosstalk occurs and an error may occur. In this case, for example, in FIG. 5A, if the angle at which one side of the octagon of the polygon mirror PM faces the axis center is γ, the regular reflection measurement system during the rotation of the polygon mirror PM from 0 to γ / 2. , And by measuring with a positive scattering reflection system with the remaining rotation of the polygon mirror PM by the remaining γ / 2 to γ, alternating measurement can be performed for each side, and crosstalk can be prevented. . For this purpose, adjustment can be performed by taking into consideration the incident angle and position on the polygon mirror PM (not shown).

  The printed solder inspection method using the displacement sensor 2a of the second embodiment can be performed in the same manner as in the first embodiment. Moreover, the form in the above [other embodiments of the displacement sensor] is also applicable to the second embodiment.

  As described above, in the present invention, since the thickness of the resist film can be estimated by including the optical system of the scattering reflection displacement measurement system and the optical system of the specular reflection displacement measurement system, the solder height from the pad surface under the resist can be estimated. You can ask for it.

It is a figure which shows the function structure of a displacement sensor and a measurement part among embodiment, Comprising: It is a figure of the form which scans and inspects between a displacement sensor and a to-be-measured object relatively. It is a figure which shows the function structure of a test | inspection part among embodiment. It is a figure which shows arrangement | positioning of the functional element which comprises the displacement sensor of FIG. It is a figure which shows the positional relationship of each light-receiving means, and demonstrates the sensitivity of each light-receiving means. It is a figure which is 2nd Embodiment, Comprising: The type of embodiment which performs an optical scan with a light source within a displacement sensor. FIG. 8 is a view for explaining and explaining a technique for estimating a resist thickness together with FIG. 7. FIG. 7 is a view for explaining and explaining a technique for estimating the resist thickness together with FIG. 6. It is a figure for demonstrating the variation in resist thickness, and its influence. It is a figure for demonstrating an ideal resist surface.

Explanation of symbols

1 substrate (printed board), 2, 2a displacement sensor, 3 data processing unit,
3a, 3b adder, 3c calculation unit, 4 scanning mechanism, 5 correction memory,
6 basic measurement unit, 7 measurement unit, 8 image processing unit, 9 comparison unit, 10 determination unit,
DESCRIPTION OF SYMBOLS 11 Display part, 12 Control part, 100 Displacement measuring part, 200 Inspection part D1 1st light-receiving means, D2 2nd light-receiving means, D3 3rd light-receiving means,
K1, K2, K3 Condensing functional element,
K1a, K2a, K3a Light-receiving lens K1b, K2b, K3b Imaging lens L1 Output of calculation unit (displacement information due to scattered reflection)
Output of L2 calculation unit (displacement information by regular reflection)
OSC1 first light source, OSC2 second light source,
OS1a laser, OSC1b half mirror,
OSC1c, OSC1d, OSC1e, OSC1g Mirror OSC2a, OSC2b Mirror OSC1f, OSC2c fθ Lens PM Polygon Mirror R Range

Claims (5)

Same as the first sensing means (OS1, D1, D2) for irradiating light perpendicularly to the measurement point on the surface of the printed board and measuring the first displacement by receiving the scattered light from the measurement point A second sensing means (OS2, D3) for measuring a second displacement by irradiating the measurement point at a predetermined angle with respect to the vertical and measuring the reflected light regularly reflected at the measurement point; Preparing a displacement sensor (2);
The displacement sensor measures the second displacement and the first displacement using the measurement point as a resist surface of the printed board, and stores a function value representing the relationship between the difference and the resist thickness in a memory. And the initial stage
A printed circuit board with solder printed on the surface pad surface is received, and the first displacement and the above-mentioned displacement are detected by the displacement sensor using the resist surface of the printed circuit board to be measured and the solder surface on the pad surface as the measurement points. A measurement stage for determining a second displacement;
Based on the difference between the first displacement and the second displacement obtained on the resist surface in the measurement step, a corresponding function value is obtained by referring to the memory, and the function value is obtained from the second displacement. Subtracting the reference position calculating step for obtaining the position of the pad surface;
A displacement calculating step of obtaining a displacement of the solder surface as a displacement from the position of the pad surface by the first displacement or the second displacement in the solder surface measured in the measuring step. Solder inspection method. First sensing means (OS1, D1) that irradiates light perpendicularly to a measurement point on the surface of the measurement printed board having a pad surface on which solder is printed and a resist surface, and receives scattered light from the measurement point. , D2) and second sensing means (OS2, D3) that illuminate the same measurement point at an angle oblique to the vertical by a predetermined angle and receive reflected light regularly reflected at the measurement point (2). And a data processing unit (3) for calculating a first displacement based on scattered light from the output of the first sensing means and a second displacement based on specular reflection light from the output of the second sensing means; A printed solder inspection apparatus comprising a measuring unit (7) for obtaining a displacement of the solder surface by the first displacement or the second displacement,
A memory (5) for storing in advance a function value representing the relationship between the difference between the second displacement and the first displacement on the resist surface and the thickness of the resist;
A basic measurement unit (6) for obtaining the first displacement and the second displacement by the displacement sensor using the resist surface of the printed board to be measured as the measurement point at the time of inspection;
Based on the difference between the first displacement and the second displacement obtained on the resist surface, a corresponding function value is obtained by referring to the memory, and the function value is subtracted from the second displacement. A reference position calculation unit (6a) for determining the position of the pad surface, and the measurement unit corrects the displacement of the solder surface from the position of the resist surface with the function value to thereby displace the solder surface. Is obtained as a displacement from the position of the pad surface. First sensing means (OS1, D1, D2) that irradiates light perpendicularly to a measurement point on the surface of the printed board and receives scattered light from the measurement point, and the same measurement point is inclined at a predetermined angle with respect to the vertical. A displacement sensor (2) including second sensing means (OS2, D3) that receives the reflected light that is irradiated at an angle of
A data processing unit (3) for calculating a first displacement based on scattered light from the output of the first sensing means and a second displacement based on specularly reflected light from the output of the second sensing means;
A memory (5) for storing in advance a function value representing the relationship between the difference between the second displacement and the first displacement and the thickness of the resist;
A basic measurement is performed in which a measurement printed board having solder printed on the surface pad surface is received, and the first displacement and the second displacement are obtained by the displacement sensor using the resist surface of the measurement printed board as the measurement point. Part (6),
Based on the difference between the first displacement and the second displacement obtained on the resist surface, a corresponding function value is obtained by referring to the memory, and the function value is subtracted from the second displacement. A reference position calculation unit (6a) for determining the position of the pad surface;
A measurement unit that obtains the first displacement or the second displacement by the displacement sensor using the solder surface of the measurement printed board as the measurement point, and obtains the displacement of the solder surface as a displacement from the position of the pad surface. (7) and a printed solder inspection apparatus. The first sensing means is formed at a first angle θ1 with respect to a first light source (OS1) that irradiates a measurement point of the printed board from a vertical direction and a first optical axis of the first light source. The first light receiving means (D1) disposed on the first scattered light path, and the second light beam is formed at a second angle θ2 on the opposite side of the first scattered light path with respect to the first optical axis. Second light receiving means (D2) disposed on the second scattered light path, and the first displacement is the sum of the output of the first light receiving means and the output of the second light receiving means. Sought after, and
The second sensing means includes a second light source (OS2) that irradiates the measurement point at an oblique angle θ3 with respect to the first optical axis, and a second light source of the second light source at the measurement point. And a third light receiving means (D3) disposed on a regular reflection optical path formed at a third angle 2θ3 with respect to the optical axis, and the second displacement is an output of the third light receiving means. The printed solder inspection apparatus according to claim 2, wherein the printed solder inspection apparatus is obtained from the following. In the displacement sensor, each of the first light receiving means, the second light receiving means, and the third light receiving means has a light receiving surface having a predetermined length, and is in accordance with a light receiving position in the predetermined length direction. A position detector for detecting optical displacement information, wherein the first optical axis, the optical axis of the second light source, the first scattered light path, the second scattered light path, and the regular reflection optical path are included in a plane. And the predetermined length direction is arranged along the plane,
Further, the first angle θ1, the second angle θ2, and the third angle 2θ3 are configured to be the same, and the angle (α1) that the first light receiving unit forms with the first scattered light path, The angle (α2) formed by the second light receiving unit with the second scattered light path and the angle (α3) formed by the third light receiving unit with the regular reflection light path are configured to be the same. Item 5. A printed solder inspection apparatus according to item 4.

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