JPH11304740A - Inspection method for filling state of conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method, for the filling state of a conductive paste, in which the continuity defect of a via hole part in a board is prevented, in which a product yield is enhanced and in which loss costs can be reduced. SOLUTION: A conductive paste 13 which is filled into a via hole 12a in a board 11 is heated. Infrared light which is radiated from the conductive paste 13 is detected. Its quantity or its time change amount is measured. Thereby, the filling state of the conductive paste 13 is detected. With reference to the conductive paste 13 which is hard to detect in conventional detecting methods and whose filling state is insufficient, whether it is good or not is detected before it is hardened, the continuity defect of the via hole 12a is prevented, a product yield can be enhanced, and loss costs can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste filling state inspection method for detecting a filling state of a conductive paste filled in a via hole in a process of manufacturing a substrate having a via hole.

[0002]

2. Description of the Related Art When a conductive paste is insufficiently filled in a via hole, conduction failure is likely to occur in a via hole portion of a substrate after the conductive paste is cured. Therefore, it is desired to prevent the conduction failure from occurring. However, since the inside of the via hole is invisible in appearance, visual inspection from the outside is difficult.

In order to detect a conductive paste in an insufficiently filled state, a method of electrically measuring the conductive paste filled in a via hole has been considered.

[0004]

However, since the conductive paste immediately after filling the via holes in the substrate is not solidified, it is difficult to apply a probe for measuring the conductivity. Also, the conductive paste does not always show a resistance value equivalent or correlated with that after curing, and furthermore, the conductive resistance of the conductive paste itself is large, so it is difficult to electrically detect the filled state of the conductive paste.

Therefore, at present, it is difficult to detect the filling state of the conductive paste to prevent the conduction failure of the via hole portion beforehand, and there is no appropriate inspection method.

Therefore, the present invention solves the above-mentioned problems, and detects the quality of the conductive paste before it is cured, thereby preventing conduction failure beforehand, thereby improving the product yield and reducing the loss cost. It is an object of the present invention to provide a conductive paste filling state inspection method capable of reducing the amount.

[0007]

Means for Solving the Problems To achieve the above object, the first invention of the present application heats a conductive paste filled in a via hole of a substrate, detects infrared light radiated from the conductive paste, and detects the infrared light. It is characterized in that the filling state of the conductive paste is detected by measuring the amount or the time change amount thereof.

According to the first aspect of the present invention, the conductive paste filled in the via hole of the substrate emits infrared light by being heated, and the amount of detected infrared light and its time change are measured. By doing so, it is possible to detect whether the conductive paste in the via hole portion is good or defective, and to prevent conduction failure in the via hole portion beforehand.

In order to achieve the above object, a second invention of the present application is to heat a conductive paste filled in a via hole of a substrate, to detect infrared light emitted from the conductive paste,
After the detected infrared light is converted into visible light, the amount of the infrared light or its time change is measured to detect the filling state of the conductive paste.

According to the second aspect of the present invention, the conductive paste filled in the via hole of the substrate is heated to convert the radiated infrared light into visible light, so that the visible light image pickup device such as a CCD camera can be used. Imaging can be performed, and the resolution of the image obtained thereby is very good, and the cost can be reduced as compared with the case where infrared light is directly imaged.

It is preferable to detect each of the infrared light emitted from the front and back surfaces of the conductive paste, and it is possible to judge good / bad by combining the detection results of the front and back surfaces. Detection can be performed accurately.

[0012] The infrared light referred to in the present specification includes far-infrared light.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for inspecting the filling state of a conductive paste according to the present invention will be described below with reference to FIGS.

In FIG. 1, which shows a schematic configuration of an inspection apparatus used in the first embodiment, reference numeral 11 denotes a substrate, 12a denotes a via hole provided in the substrate 11, and 13 denotes a conductive paste filled in the via hole 12a. The via hole 1
The portion consisting of 2a and the conductive paste 13 and the vicinity thereof is referred to as a via hole portion 12.

Numeral 14 denotes an infrared light image pickup device, which picks up an image of infrared light 18 from the via hole portion 12 in order to prevent a conduction failure of the conductive paste 13 beforehand. In the first embodiment, the infrared light imaging device 14 images each of the infrared light 18 radiated from both the front surface and the back surface of the conductive paste 13. Reference numeral 15 denotes a light source device that heats the via hole portion 12, and reference numeral 16 denotes a lens that collects emitted light such as laser light from the light source device 15. Reference numeral 17 denotes an information processing device, which inputs information such as the amount of infrared light 18 detected by the infrared light imaging device 14 and the amount of change over time, and analyzes the filling state of the conductive paste 13.

The conductive paste 13 in the above inspection apparatus
The method of inspecting the state of filling will be described. First, the laser light from the light source device 15 is applied to the vicinity of the via hole 12 of the substrate 11 by the lens 16. Then, the conductive paste 13 in the via hole portion 12 is heated to generate a thermal effect.
Is emitted. Then, the amount of radiation of the infrared light 18 after light irradiation from the light source device 15 is imaged by the infrared light imaging device 14. Further, since the thermal effect of the via hole portion 12 is also transmitted and radiated to the back surface, the amount of the infrared light 18 is similarly captured by the infrared light imaging device 14 provided on the back surface side.

FIG. 2 is a cross-sectional view schematically showing good or bad filling state of the conductive paste 13 in the via hole portion 12 (FIG. 1). 21 is a substrate, 22 is a good via-hole portion in a normal filling state, 23 is a defective via-hole portion into which foreign matter 23a such as debris of the substrate has entered, and 24 is a conductive vial of conductive paste 13 because the processing hole diameter 24a of the via hole is small. Defective via hole portion with small filling amount, 25 is conductive paste 13
A defective via hole portion 26 having a small filling amount of the conductive paste 13 due to the recess 25a on the front surface (or the back surface) of the
Is a defective via hole portion in which the conductive paste 13 has come off and the through hole 26a has been opened.

FIG. 3 shows the above-described good / bad via hole portions 2.
It is the graph which showed typically the amount of infrared light radiation radiated | emitted from the surface of No. 2-26. That is, for each of the good and bad via hole portions 22 to 26, a light beam from a heating light source such as a laser beam is applied to each of the via hole portions 22 to 26 using the inspection apparatus shown in FIG. Beer hole 2
It is a graph of numerical values obtained by measuring the amount of infrared light radiation detected on the surface side of Nos. 2 to 26. In this graph, reference numeral 31 denotes the amount of infrared light emitted from the good via hole portion 22 in the normally filled state shown in FIG. The amount of infrared light radiated in the via hole 24, the amount of infrared light radiated in the defective via hole 25 due to the depression, and the amount of the defective via hole 26 caused by the through hole
Is the amount of emitted infrared light. 36, 37, 38, and 39 indicated by hatching indicate defective via hole portions 2 respectively.
The difference between the amount of infrared light radiation of 3 to 26 and the amount of infrared light radiation of the good via hole portion 22 is shown.

FIG. 4 shows the above-described good / defective via hole portions 2.
It is the graph which showed typically the amount of infrared light radiated | emitted from the back surface of No. 2-26. That is, similarly to FIG. 3, the graph is obtained by measuring the numerical values obtained by measuring the amount of infrared light radiation detected on the back surface side of the good and bad via hole portions 22 to 26.
In this graph, reference numeral 41 denotes the amount of infrared light emitted from the good via hole portion 22, and reference numeral 42 denotes the defective via hole portion 2 due to foreign matter.
3, reference numeral 43 denotes the amount of infrared light emitted from the defective via hole portion 24 having a small processing hole diameter, reference numeral 44 denotes the amount of infrared light emitted from the defective via hole portion 25 due to the depression, and reference numeral 45 denotes
Is the amount of infrared light radiated from the defective via hole 26 due to the through hole. Also, 46, 47, and 4 indicated by hatching
Numerals 8 and 49 indicate the difference between the amount of infrared light emitted from the defective via hole portions 23 to 26 and the amount of infrared light emitted from the good via hole portion 22, respectively.

FIG. 5 shows FIGS. 3 (front side) and FIG. 4 (back side)
Is a graph schematically showing the infrared light radiation amount obtained by adding the absolute value of the difference from 31 to 41 of the good via hole portion for each defective via hole portion among the measurement results of the infrared light radiation amount indicated by. is there. In this graph, 51 is the sum of the absolute values (= 0) of the infrared light radiation amounts 31 and 41, 52 is the sum of the absolute values of the infrared light radiation amounts 32 and 42, and 53 is the infrared light radiation amounts 33 and 4.
2 is the sum of absolute values, 54 is the sum of the absolute values of the infrared radiation amounts 34 and 44, and 55 is the sum of the absolute values of the infrared radiation amounts 35 and 45.
When the sum of the absolute values of the respective radiation amounts exceeds the threshold value, the filling state of the conductive paste in the via holes is regarded as defective. Thus, by combining the measurement results of the amount of infrared light radiation from the front and back surfaces of each via hole,
For example, the defect detection ability can be improved as compared with the inspection on the front side only.

FIG. 6 shows a schematic configuration of an inspection apparatus used in the second embodiment. In this embodiment, the infrared light 18 radiated from the conductive paste 13 of the via hole 12
Is converted into visible light, and the amount of the conductive paste 13 is detected by measuring the amount or the amount of change with time.
In the first embodiment, the infrared light imaging device 14 is used to detect the infrared light 18, whereas in the second embodiment, the infrared light 18 radiated from the front and back surfaces of the conductive paste 13 is used. Is temporarily received by a visible light conversion element 63 that converts the light into visible light, and the visible light conversion element 63 is imaged by a visible light image pickup device 64 such as a CCD camera to detect the infrared light 18. It is preferable that the visible light conversion element 63 employs a so-called stimulable luminous body.

As in the first embodiment, 11 is a substrate, 12
a is a via hole provided in the substrate 11, 13 is a conductive paste filling the via hole 12a, and 12 is a via hole portion 12. Reference numeral 15 denotes a light source device that heats the via hole portion 12, and reference numeral 16 denotes a lens that collects light emitted from the light source device 15. Reference numeral 17 denotes an information processing device, which inputs information such as the amount of infrared light 18 detected from the front and back surfaces of the via hole portion 12 and the amount of change with time by the visible light imaging device 64 and analyzes the filling state of the conductive paste 13. . The principle of detecting a defect based on image information after imaging is the same as that of the first embodiment, but by converting the infrared light 18 into visible light, the resolution of the image is improved, CCD instead of imaging device
Since a visible light imaging device such as a camera can be used, the cost can be reduced.

FIG. 7 is a schematic diagram showing a third embodiment. In the present embodiment, except that IH (electromagnetic induction heating) is used as the heating means, it is the same as the above-described basic configuration of the detection device and the means for detecting a defective filling state of the conductive paste 13.

In the third embodiment, as a means for heating the conductive paste 13 in the via hole portion 12, the light from the light source device is not condensed and used.
A high-frequency current is applied to the coil 72 arranged in the vicinity, and this high-frequency current causes an electromagnetic induction effect on the conductive paste 13,
Heated. By reducing the size of the coil 72 and arranging the plurality of coils 72, the via hole portion 12 of the substrate 11 can be selectively heated.

[0025]

As described above, according to the present invention, a conductive paste having an insufficient filling state, which has been difficult to detect by the conventional inspection method, can be used before it is cured.
Prevent continuity failure by detecting failure,
Provided is a conductive paste filling state inspection method capable of improving the product yield and reducing the loss cost and converting the radiated infrared light into visible light so that the detection can be performed accurately at a low cost. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire configuration of an inspection apparatus used in a first embodiment of the present invention.

FIG. 2 is a sectional view schematically showing an example of a defective filling state of a conductive paste in the embodiment.

FIG. 3 is a graph schematically showing the amount of infrared light emitted from the surface of a via hole in the embodiment.

FIG. 4 is a graph schematically showing the amount of infrared light emitted from the back surface of the via hole in the embodiment.

FIG. 5 is a graph schematically showing a composite of the detection results of the amount of infrared light radiation shown in FIGS. 3 and 4;

FIG. 6 is a schematic diagram showing an entire configuration of an inspection device used in a second embodiment of the present invention.

FIG. 7 is a schematic diagram showing a configuration of a main part of an inspection device used in a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Via hole part 12a Via hole 13 Conductive paste 14 Infrared light imaging device 15 Light source device 16 Lens 17 Information processing device 18 Infrared light 22 Good via hole part 23-26 Bad via hole part 63 Visible light conversion element 64 Visible light imaging device 72 Coil for passing high-frequency current

Claims (5)

[Claims] 1. A method of filling a conductive paste by heating a conductive paste filled in a via hole of a substrate, detecting infrared light emitted from the conductive paste, and measuring an amount of the infrared light or a time change thereof. A conductive paste filling state inspection method, characterized by detecting a state. 2. A method of heating a conductive paste filled in a via hole of a substrate, detecting infrared light radiated from the conductive paste, converting the detected infrared light into visible light, and then converting the amount or the time. A conductive paste filling state inspection method, comprising detecting a filling state of a conductive paste by measuring a change amount. 3. As means for heating the conductive paste,
3. The method according to claim 1, wherein a laser beam is used. 4. As means for heating the conductive paste,
3. The method according to claim 1, wherein electromagnetic induction heating is used. 5. The conductive paste filling state inspection method according to claim 1, wherein infrared light emitted from the front surface and the back surface of the conductive paste is detected.