JP2001228099A - Plating inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate with high accuracy as to whether plating is applied from a monochromatic image. SOLUTION: A substrate and a plated metal are irradiated with a light of a specific wavelength which is different by a large amount in reflectivity from other wavelength region to obtain a monochromatic image, based on the light having a specific wavelength, and the monochromatic image is converted into a binary image to discriminate between the plated metal and the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting whether or not a base is plated with metal, and more particularly to a plating method suitable for detecting whether or not gold is plated on a copper base. Related to inspection method.

[0002]

2. Description of the Related Art A semiconductor device, a CSP (Chip S)
In size packages, external terminals made of solder balls are arranged in a matrix on the back surface of the package in order to cope with miniaturization of the device (package) and increase in the number of terminals. A package substrate on which a semiconductor chip of such a semiconductor device is mounted is generally formed of a polyimide resin or the like, and a wiring pattern connected to a terminal portion of the semiconductor chip is formed on one side surface (surface).
Circular gold-plated external terminals for mounting solder balls on the back side are formed in a matrix. The external terminals are gold-plated on a copper base formed by plating or the like. Conventionally, when inspecting whether or not gold plating is performed on a copper base, a white light is irradiated on the back surface of the package substrate and photographed by a monochrome CCD, and a binary image is formed from monochrome image data. Then, it was determined whether or not gold plating had been performed.

[0003]

Since gold and copper have different colors, they can be easily distinguished when viewed with the naked eye or a color image. However, there is not much difference between the reflectances of gold and copper for white light, and the brightness of a monochrome image by white light is almost the same. For this reason, when obtaining a binary image from a monochrome image by white light, and inspecting whether or not the copper base is gold-plated based on the binary image,
It becomes difficult to distinguish between the gold part and the copper part depending on the light irradiation angle or the like, and an inspection error often occurs. In order to avoid such inconvenience, it is conceivable to obtain and inspect a color image, but discrimination based on a color image requires more time than that based on a monochrome image, and the inspection speed is reduced. Not only that, the equipment is expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object to make it possible to determine from a monochrome image whether plating has been performed with high accuracy.

[0005]

SUMMARY OF THE INVENTION The inventors of the present invention have studied a method of reliably determining whether or not gold plating has been performed on the basis of a binary image obtained from a monochrome image. When the reflectance of gold and copper with respect to was measured, it was found that there was a greater difference between the reflectances of the two in the specific wavelength region. The present invention has been made based on this finding, and the gold plating inspection method according to the present invention obtains a monochrome image to be inspected and determines whether or not gold plating has been performed based on the monochrome image. In the inspection method, with the base and the plated metal, the inspection object is irradiated with light having a specific wavelength that is significantly different in reflectance from other wavelength regions, and a monochrome image based on the light having the specific wavelength is obtained. I have.

[0006]

According to the present invention constructed as described above, since the base and the plating metal irradiate light of a specific wavelength whose reflectance is much different from that of other wavelength regions, the brightness of the obtained monochrome image (level Tone) differs greatly between the underlayer and the plated metal. For this reason, for example, when a binary image is created from a monochrome image, it is possible to increase the difference between the gradation indicating the base and the gradation indicating the plated metal and the threshold value, and the accuracy of the binary image for discriminating between the two. And it is possible to easily and reliably determine whether or not plating has been performed, and it is possible to perform plating inspection with high accuracy. For this reason, for example, it is possible to easily distinguish between copper and gold, which have little difference in reflectance for white light, and easily determine whether or not gold is plated on a copper base, It is possible to reliably determine.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a plating inspection method according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows the reflectance of pure copper and pure gold with respect to the wavelength of light. In the figure, the curve connecting the black circles indicates the reflectance of gold, and the curve connecting the squares indicates the reflectance of copper. As is clear from FIG. 1, light having a wavelength of 0.4 μm or less and wavelength of 0.5 μm are used.
There is no significant difference in the reflectance between gold and copper for light of 9 μm or more. And the wavelength is about 0.33 μm to about 0.52 μm
For light between the two, copper has a higher reflectance than gold. In particular, for light having a wavelength of about 0.45 μm, the reflectance of copper is about 17 to 18% higher than the reflectance of gold.

However, the wavelength is about 0.52 μm to about 0.1 μm.
For light of 59 μm, the reflectivity of gold is higher than that of copper. In particular, for light having a wavelength of about 0.55 μm, the reflectance of gold is about 16% higher than that of copper. For this reason, when irradiating white light to gold and copper, there is no large difference in the reflectance between the two with respect to white light.

Therefore, the wavelength having a large difference between the two reflectances is about 0.45 μm or 0.55 μm.
By irradiating the front and rear lights to the inspection object having a gold plating on the copper base and obtaining a monochrome image based on the light, the brightness (gradation) of the copper portion and the brightness of the gold portion are different from each other. A large gradation difference that cannot be obtained with a wavelength can be obtained.
Therefore, when a threshold value for discriminating between the two is set, the difference between the gradation indicating copper and the gradation indicating gold and the threshold is large, so that copper and gold can be easily distinguished. it can. Therefore, when gold plating is applied to the copper base,
By irradiating light having a wavelength of about 0.45 μm or about 0.55 μm to obtain a monochrome image, it is possible to easily and reliably determine whether or not gold plating is performed.

FIG. 2 shows an example of an inspection apparatus to which the plating inspection method of the present invention is applied. In FIG.
The package substrate 10 to be inspected is placed on the transport device 12 with the front surface on which a semiconductor chip (not shown) is mounted on the lower side and the back surface on which the solder balls are mounted on the upper side.
As shown in FIG. 4, the sheet is conveyed rightward in FIG. Then, on the back surface of the package substrate 10, gold plating (both not shown) is applied on a copper base plating at positions where solder balls are to be mounted. The inspection apparatus is provided with a base detection unit 20 a and a gold plating detection unit 20 b along the transport device 12.

The underlayer detection section 20a and the gold plating detection section 20b
Are configured in substantially the same manner. Then, each detection unit 20
a and 20b are provided with light sources 22a and 22b for irradiating the package substrate 10 transported by the transport device 12 with light. The light source 22a emits monochromatic light having a wavelength of, for example, 0.45 μm, and the light source 22b emits monochromatic light having a wavelength of, for example, 0.56 μm.
m monochromatic light is emitted. Each of the detection units 20a and 20b has a monochrome CCD 24 (24a, 24b) disposed above the transport device 12,
Package substrate 1 through which monochrome CCD 24 passes below
2 and outputs an analog monochrome image signal to the A / D converter 26 (26a, 26b). A / D converter 2
Reference numeral 4 converts the analog image signal output from the monochrome CCD 24 into a digital signal of, for example, 256 gradations according to the brightness of the image and outputs the digital signal.

A memory 28 (28a, 28b) connected to the output side of the A / D converter 26 temporarily stores one frame of digital image signal. And memory 2
8, the binarization circuit 30 (30a, 30b)
The image signal stored in the memory 28 is read out, a binary image is created based on a threshold value given in advance, and sent to the comparison / determination unit 32 (32a, 32b).

The comparing and judging section 32 outputs signals from the binarizing circuits 30 to 2
When the value image data is input, the reference pattern output unit 3
4 (34a, 34b), a reference pattern is inputted, and the copper portion of the package substrate 10 photographed by comparing the two matches the reference pattern, or the portion to be gold-plated is gold-plated. Is determined. Then, the comparison determination unit 32 outputs the determination result to the corresponding display device 36 (36a, 36b) or a printer (not shown).

In the inspection apparatus configured as described above, the underlayer detecting section 20a detects the copper underlayer and other copper patterns as follows, and the gold plating detecting section 20b detects the gold-plated section. I do.

The light source 22a of the base detection unit 20a irradiates the package substrate 10 with monochromatic light having a wavelength of 0.45 μm. The monochrome CCD 24a photographs the package substrate 10 and outputs a monochrome analog image signal (analog image data) based on light having a wavelength of 0.45 μm. A
The / D converter 26a converts the analog image data into, for example, 25
The data is converted into digital image data of 6 gradations and stored in the memory 28a.
Output to Then, the binarization circuit reads the image data stored in the memory 28a, compares this data with a predetermined threshold value, for example, a gradation value corresponding to a reflectance of 46%, and determines the copper portion. A binary image having a bright part and other parts as dark parts is created and output to the comparison and determination unit 32a. The comparison determination unit 32a compares the binary image created by the binarization circuit 30a with the reference pattern stored in the reference pattern output unit 34a, and determines whether the binary image matches the reference pattern, The determination result is displayed on the display device 36a or output to a printer or the like.

The monochrome CCD 24a of the background detector 20a
Is transported below the monochrome CCD 24b of the gold plating detection unit 20b, the light source 22b emits light having a wavelength of, for example, 0.56 μm. Then, in the gold plating detecting unit 20b, the monochrome CCD 24b outputs monochrome analog image data based on light having a wavelength of 0.56 μm. This analog data is converted into a digital signal in the same manner as described above, and is temporarily stored in the memory 28b. Further, the binarization circuit 30b of the gold plating detection unit 20b includes a base detection unit 20a.
As in the case of the above, the data stored in the memory 28b is compared with a predetermined threshold value (for example, a gradation corresponding to a reflectance of 76%), and the gold-plated portion is defined as a bright portion, and the other portions are defined as A binary image as a dark portion is created and sent to the comparison / determination unit 32b. The comparison / determination unit 32b includes a binarization circuit 3
By comparing the binary image created by Ob with the reference pattern stored in the reference pattern output unit 34b, it is determined whether or not a predetermined position is plated with gold, and the result is output to the display device 36 or the like.

As described above, in the inspection apparatus according to the embodiment, the package substrate 10 is irradiated with light of a wavelength having a reflectivity much different from that of the other wavelength region using copper and gold, and a monochrome image is formed based on the light. Because of this, it is possible to easily distinguish between gold and copper, whose reflectances are not so different in white light, and whether gold is applied to a predetermined position or not, and unnecessary portions are gold-plated. It is possible to easily determine whether or not there is. In addition, copper is detected using light that has a higher reflectance than gold, and copper is detected, and gold is detected using gold that has a higher reflectance than copper. Therefore, not only can a gold-plated portion be detected more reliably, but also it is possible to easily and reliably know whether or not a copper base portion that does not need to be gold-plated is gold-plated.

In the above-described embodiment, the case where the light having the wavelength of 0.45 μm is used to detect the copper portion has been described.
Light of about 5 μm to about 0.5 μm can be used. Further, in the above-described embodiment, the case where the light having the wavelength of 0.56 μm is used to detect the gold-plated portion has been described. However, when the gold-plated portion is detected, about 0.53 μm to about 0.57 μm is used. Light can be used. And in the said embodiment,
Although the case where the detection of the base is different from the detection of the gold plating has been described, the base metal and the gold plating may be detected by switching the light source or the like at the same place. Further, in the above embodiment,
Although the case where gold plating is applied to the copper base has been described, by determining the reflectance for the wavelength of various metals and various substances, it is possible to irradiate light with greatly different reflectance between the arbitrary base and the plating metal. By obtaining a monochrome image, the base and the plated metal can be easily distinguished,
Whether or not plating has been performed can be easily and reliably determined.

[0019]

As described above, according to the present invention, since the base and the plating metal irradiate light of a specific wavelength whose reflectance is much different from that of the other wavelength regions, the obtained monochrome is obtained. The brightness (gradation) of the image greatly differs between the base and the plated metal, and when a binary image is created from a monochrome image, for example, the difference between the gradation indicating the base and the gradation indicating the plated metal increases. In addition, the accuracy of the binary image that distinguishes the two is improved, and whether or not plating is performed can be easily and reliably determined, and the plating inspection can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the wavelength of light and the reflectance for pure copper and pure gold.

FIG. 2 is a diagram showing an example of an inspection apparatus to which the plating inspection method of the present invention is applied.

[Explanation of symbols]

10 ... inspection object (package substrate), 20a ...
Underlayer detecting section, 20b ... Gold plating detecting section, 22a, 2
2b: Light source, 24a, 24b: Monochrome CC
D, 30a, 30b ... binarization circuit, 32a, 32b
............ Comparative judgment unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // H01L 23/12 H01L 23/12 L

Claims (1)

[Claims] 1. A plating inspection method for obtaining a monochrome image to be inspected and determining whether or not plating has been performed based on the monochrome image, wherein the base and the plated metal have a higher reflectance than other wavelength regions. A plating inspection method comprising: irradiating the inspection target with light having a specific wavelength that is significantly different from the inspection target; and obtaining a monochrome image based on the light having the specific wavelength.