Inspection system

Abstract

The present invention proposes an inspection system that is capable of highly accurately inspecting device characteristics of an optical module, particularly a CPO module in a set temperature range. An inspection system according to the present disclosure comprises: an evaluation board having a subject provided thereon; and a temperature control device provided at a position that is perpendicular to the surface of a substrate of the evaluation board which has the subject provided thereon and that is on the side of the surface on which the subject is provided and / or the side opposite from the surface. The evaluation board further includes a first chip in which a variation in characteristic due to a change in temperature during inspection is less than a first threshold value and a second chip in which a variation in characteristic due to a change in temperature during inspection is equal to or greater than a second threshold value. The subject, the temperature control device, and the first chip are provided inside a prohibition region that is set in the evaluation board, and the second chip is provided outside the prohibition region.

Description

Inspection System

[0001] The present disclosure relates to inspection systems, and more particularly to inspection systems for integrated devices such as optical modules.

[0002] In the field of optical communications, in order to increase communication capacity and reduce power consumption, CPO (Co-Packaged Optics) modules are attracting attention. CPO modules integrate multiple devices, such as optical chips, analog ICs, and signal processing LSIs, which were previously packaged individually, into a single package.

[0003] The optical chips, analog ICs, and signal processing LSIs integrated into such CPO modules have characteristics (the performance of each element) that change with temperature. Therefore, in pre-shipment inspections, it is necessary to confirm that the device meets shipping standards at all temperatures within the operating temperature range supported by the product specifications (for example, a range of -5°C to 90°C).

[0004] In conventional pre-shipment inspections of optical devices, the optical device is placed in a thermostatic chamber or brought into contact with a temperature control device such as a Peltier element, and the characteristics of the optical device are evaluated while controlling the temperature.On the other hand, in conventional pre-shipment inspections of analog ICs and signal processing LSIs, the characteristics of the analog ICs and signal processing LSIs are evaluated while controlling the temperature by blowing temperature-controlled air onto the device using a thermostreamer.

[0005] However, when such a technique is applied to a CPO module, the following problems arise.

[0006] For example, if an attempt is made to control the temperature of a CPO module using a temperature control device such as a thermostatic bath or Peltier element, in a device in which a CPO module is mounted (hereinafter referred to as a CPO device), the voltage supply IC and chip components for stabilizing the supply voltage located near the CPO module will also be affected by the temperature control device and change in temperature, making it impossible to accurately evaluate the characteristics of the CPO module. This is because a CPO device requires that the voltage supply IC and chip components for stabilizing the supply voltage be located near the CPO module.

[0007] On the other hand, if an attempt is made to control the temperature of a CPO module using a thermostreamer, the temperature-control wind will hit the optical fiber used for the optical signal input and output of the CPO device, causing the optical fiber to vibrate and resulting in fluctuations in the optical signal, which similarly makes it impossible to accurately evaluate the characteristics of the CPO module.

[0008] As another example, a method is known in which an IC socket for an optical module is brought into contact with a temperature adjustment element, and the temperature of the optical module is controlled to evaluate the characteristics of the optical module (see, for example, Patent Document 1). However, while this method is effective for configurations such as conventional optical modules that do not require a voltage supply IC or a chip component for stabilizing the supply voltage, it is not suitable for CPO modules that require a voltage supply IC or a chip component for stabilizing the supply voltage to be installed nearby.

[0009] Japanese Patent Application Laid-Open No. 2022-189071

[0010] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to propose an inspection system that can inspect the characteristics of optical modules, particularly CPO modules, with high accuracy within a set temperature range.

[0011] In response to the above-described problems, the present disclosure provides an inspection system including an evaluation board on which a test object is placed, and a temperature control device placed on a substrate of the evaluation board in a position perpendicular to a surface on which the test object is placed and on at least one of the side of the surface on which the test object is placed and the back side of the surface, wherein the evaluation board further includes a first chip whose characteristic variation due to temperature changes during inspection is less than a first threshold, and a second chip whose characteristic variation due to temperature changes during inspection is equal to or greater than a second threshold, and wherein the test object, the temperature control device, and the first chip are placed inside a prohibited area provided on the evaluation board, and the second chip is placed outside the prohibited area.

[0012] 1A and 1B are diagrams conceptually showing the configuration of an inspection system 100 according to a first embodiment of the present disclosure, where (a) is a top view and (b) is a cross-sectional view taken along the line Ib-Ib. 1B are diagrams conceptually showing the configuration of an inspection system 200 according to a second embodiment of the present disclosure, where (a) is a top view and (b) is a cross-sectional view taken along the line IIb-IIb. 1C are diagrams conceptually showing the configuration of an inspection system 300 according to a third embodiment of the present disclosure, where (a) is a top view and (b) is a cross-sectional view taken along the line IIIb-IIIb. 1D are diagrams conceptually showing the configuration of an inspection system 400 according to a fourth embodiment of the present disclosure, where (a) is a top view and (b) is a cross-sectional view taken along the line IVb-IVb. 1E are diagrams conceptually showing the configuration of an inspection system 500 according to a fourth embodiment of the present disclosure, where (a) is a top view and (b) is a cross-sectional view taken along the line Vb-Vb. 6A and 6B are diagrams conceptually showing the configuration of an inspection system 600 according to a fourth embodiment of the present disclosure, in which FIG. 6A is a top view and FIG. 6B is a cross-sectional view taken along the line VIb-VIb.

[0013] Various embodiments of the present disclosure will be described in detail below with reference to the drawings. The same or similar reference numerals indicate the same or similar elements, and redundant description may be omitted. Numerical values ​​are for illustrative purposes and are not intended to limit the technical scope of the present disclosure. Furthermore, the following description is an example, and some configurations may be omitted or modified, or additional configurations may be added, as long as they do not deviate from the gist of one embodiment of the present disclosure.

[0014] The inspection system according to the present disclosure includes an evaluation board on which a CPO module (a test object) is mounted, and a temperature control device installed perpendicular to the surface (hereinafter referred to as the main surface) of the evaluation board substrate on which the CPO module is mounted, and which controls the temperature of the CPO module. The evaluation board further includes a first chip having a small temperature characteristic (characteristic fluctuation due to temperature changes during inspection is less than a first threshold) and a second chip having a large temperature characteristic (characteristic fluctuation due to temperature changes during inspection is equal to or greater than a second threshold). Additionally, the evaluation board has a prohibited area, and the CPO module, temperature control device, and first chip are installed inside the prohibited area. Meanwhile, the second chip is installed outside the prohibited area.

[0015] The first chip is a chip component that simulates a voltage supply IC and a supply voltage stabilization chip that are installed near the CPO module in a CPO device, while the second chip is a chip component that simulates an element (e.g., a DC / AC converter) that does not necessarily need to be installed near the CPO module in a CPO device.

[0016] The inspection system according to the present disclosure is configured such that, in evaluating the characteristics of the CPO module, only the temperature of the CPO module under test is controlled. Furthermore, because the first and second chips are respectively installed inside and outside the prohibited area, it is possible to perform a temperature characteristic evaluation that simulates the actual implementation of a CPO device. Therefore, the inspection system according to the present disclosure is capable of performing more accurate inspections than the conventional techniques described above.

[0017] 1A and 1B are diagrams conceptually illustrating the configuration of an inspection system 100 according to a first embodiment of the present disclosure, with (a) illustrating a top view and (b) illustrating a cross-sectional view taken along the line Ib-Ib. As shown in Fig. 1, inspection system 100 includes an evaluation board 110 on which a CPO module under test is installed, and a temperature control device 120 that controls the temperature of the CPO module under test. Evaluation board 110 also includes a substrate 111, and, within the surface of substrate 111 on which the CPO module under test is installed (hereinafter referred to as the main surface), a prohibited area 112 in which the CPO module under test and temperature control device 120 are installed, a first chip 113 installed within prohibited area 112 on the main surface, and a second chip 114 installed outside prohibited area 112 on the main surface.

[0018] The prohibited area 112 corresponds to an area on the main surface where the CPO module, the temperature control device 120, and the first chip 113 are installed. The range of the prohibited area 112 is determined based on the ambient temperature of the testing environment, the controlled temperature of the temperature control device 120 during testing, and the thermal properties (thermal conductivity, thermal resistance, etc.) of the substrate 111. For example, if the ambient temperature of the testing environment (room temperature) is 20°C and the controlled temperature during testing is −5°C to 90°C, the controlled temperature at which the temperature difference between room temperature and the controlled temperature is greatest is 90°C, resulting in a temperature difference of 70°C. Therefore, the range of the prohibited area 112 is determined so that the temperature outside the prohibited area 112 on the substrate 111 (the range where the second chip is installed) is 70°C or less.

[0019] As described above, the first chip 113 is a chip component that simulates a voltage supply IC and a supply voltage stabilizer chip that are installed near the CPO module, and has temperature characteristics whose characteristic fluctuations during testing are less than a first threshold (e.g., 10%). Similarly, the second chip 114 is a chip component that simulates an element in a CPO device that does not necessarily need to be installed near the CPO module, and has temperature characteristics whose characteristic fluctuations during testing are equal to or greater than a second threshold (e.g., 10%). Note that while FIG. 1 depicts four first chips 113 (first chips 113a-d) and seven second chips 114 (second chips 114a-g), this is for illustrative purposes only, and any number of chips may be installed depending on the design.

[0020] The temperature control device 120 has a function of controlling the temperature of the CPO module, which is the test object, and may be, for example, a Peltier element. As described above, the temperature control device 120 is installed in a position perpendicular to the main surface of the evaluation board. In FIG. 1 , the temperature control devices 120 are depicted as being installed one on the main surface side of the substrate 111 and one on the surface opposite the main surface (hereinafter referred to as the back surface) so as to sandwich the CPO module and evaluation board 110. However, it is sufficient that the temperature control devices 120 are installed on at least one of the main surface side and the back surface side of the substrate 111.

[0021] During testing, the CPO module under test is connected within the prohibited area 112 of the evaluation board 110. At this time, it is desirable to connect the CPO module so as to simulate the form in which it is actually mounted on the CPO device. For example, if it is assumed that the CPO module will be mounted on the CPO device in the form of a ball grid array (BGA) module, the CPO module may be installed on the substrate 111 of the evaluation board 110 via a ball grid 115, as shown in FIG. 1 .

[0022] Using the inspection system 100 having such a configuration, an operational test can be performed while controlling the temperature of the CPO module under test within a predetermined range, thereby obtaining the operational performance of the CPO module within the predetermined temperature range. Since the inspection system 100 can perform an operational test simulating an actual CPO device while controlling the temperature of only the CPO module, it is possible to perform an inspection with higher accuracy than the conventional technology described above.

[0023] 2A and 2B are diagrams conceptually illustrating the configuration of an inspection system 200 according to a second embodiment of the present disclosure, with (a) illustrating a top view and (b) illustrating a cross-sectional view taken along the line IIb-IIb. In addition to the configuration of the inspection system 100 described above, the inspection system 200 according to this embodiment further includes a spacer 210 that is installed between the back surface of the substrate 111 of the evaluation board 110 and the temperature control device 120b. Additionally, the spacer 210 includes a groove 211 having an opening on the surface on the back side of the substrate 111, and the first chip 113 is configured to be installed inside the groove 211 and on the back surface of the substrate 111.

[0024] The inspection system 200 is intended to be configured to shorten the distance between the first chip 113 and the CPO module being inspected. To achieve this configuration, a spacer 210 is installed to ensure a space for the first chip 113 to be installed directly below the CPO module. This space where the first chip 113 is installed corresponds to the groove 211.

[0025] The groove 211 is preferably non-through (having a bottom surface) so as not to be directly affected by the temperature of the temperature control device 120b.

[0026] 2 shows two grooves 211 (grooves 211a and 211b) with three first chips 113 (first chips 113a-c) arranged in groove 211a and one first chip 113 (first chip 113d) arranged in groove 211b. However, groove 211 may have any shape depending on the design, and the number of first chips 113 arranged may also be any number depending on the design. However, if groove 211 has a shape that penetrates in the thickness direction (direction perpendicular to the main surface), first chip 113 will be directly affected by temperature changes caused by temperature control device 120b, which may cause a decrease in inspection accuracy. Therefore, it is desirable that groove 211 have a shape that does not penetrate in the thickness direction (has a bottom surface).

[0027] The inspection system 200 having such a configuration is configured to further shorten the distance between the first chip 113 and the CPO module under test, which not only realizes high-precision inspection but also provides the effect of stabilizing the voltage supply from the first chip 113 during the performance test.

[0028] 3A and 3B are diagrams conceptually illustrating the configuration of an inspection system 300 according to a third embodiment of the present disclosure, in which (a) is a top view and (b) is a cross-sectional view taken along the line IIIb-IIIb. In addition to the configuration of the inspection system 100 described above, the inspection system 300 according to this embodiment further includes a sealed box 310 for enclosing the evaluation board 110.

[0029] Depending on the environment during the operational test, environmental factors may cause a decrease in test accuracy. For example, if the controlled temperature during the operational test is lower than the ambient temperature, particularly if it is below 0°C, moisture in the environment may condense and adhere to the evaluation board 110. This may result in short circuits between the first chips 113, leading to failure and a decrease in test accuracy. The sealed box 310 is an additional component intended to prevent a decrease in test accuracy due to such an environment.

[0030] In addition, in Figure 3, a part of the temperature control device 120 is depicted as protruding outside the sealed box 310, but as long as the entire evaluation board 110 is configured to be enclosed, it may have any shape, and the entire temperature control device 120 may also be configured to be enclosed.

[0031] The inspection system 300 having such a configuration can suppress the occurrence of malfunctions and deterioration of inspection accuracy caused by the above-mentioned environment, thereby enabling even more accurate inspections. For example, if dry air is filled inside the sealed box 310 during an operation test, condensation can be suppressed even if the controlled temperature is 0°C or below.

[0032] 4A and 4B are diagrams conceptually illustrating the configuration of an inspection system 400 according to a fourth embodiment of the present disclosure, with (a) illustrating a top view and (b) illustrating a cross-sectional view taken along the line IVb-IVb. In addition to the configuration of the inspection system 100 described above, the inspection system 400 according to this embodiment further includes a socket jig 410 that is electrically connected to the substrate 111 and in which a CPO module to be inspected is installed.

[0033] The socket jig 410 is a component, such as an IC socket, that electrically connects the CPO module and the board 111. In the inspection system 400, the socket jig 410 is electrically connected to the board 111 in advance, so that an operational test can be performed simply by placing the CPO module under test inside the socket jig 410. This eliminates the need for mounting by soldering or the like each time an operational test is performed, which has the advantage of shortening the time required for the inspection.

[0034] The socket jig 410 may be included in the above-described inspection systems 200 and 300, as in the inspection systems 500 and 600 shown in FIGS.

[0035] In the explanation so far, the configuration of the inspection system according to the present disclosure has been described using the example of the test object being a CPO module, but the test object is not limited to a CPO module and may be an optical module or an integrated device having another configuration.

[0036] As described above, the inspection system according to the present disclosure is configured to be able to control the temperature of only the optical module under test. Additionally, by providing a prohibited area on the evaluation board, the placement of chips that must be installed near the optical module under test (those with a temperature change of less than 10%) and those that do not (those with a temperature change of 10% or more) can be clearly distinguished in the device on which the optical module under test is mounted, enabling highly accurate inspection. Such an inspection system is expected to be used as an inspection technique for quality assurance and quality control of CPO modules.

Claims

1. An inspection system comprising: an evaluation board on which a test object is placed; and a temperature control device installed in a position perpendicular to a surface of a substrate of the evaluation board on which the test object is placed, and in at least one of the positions on the side of the surface on which the test object is placed and the back side of the surface; wherein the evaluation board further comprises: a first chip whose characteristic variation due to temperature change during inspection is less than a first threshold value; and a second chip whose characteristic variation due to temperature change during inspection is equal to or greater than a second threshold value; wherein the test object, the temperature control device, and the first chip are placed inside a prohibited area provided on the evaluation board, and the second chip is placed outside the prohibited area.

2. The inspection system according to claim 1, further comprising: a temperature control device disposed at a position on the back surface side; and a spacer disposed between the substrate and the temperature control device disposed at the position on the back surface side; and the first chip is disposed on the back surface of the substrate and within a groove formed in the spacer.

3. The inspection system according to claim 1, further comprising a sealed box arranged to enclose the entire evaluation board.

4. The inspection system according to any one of claims 1 to 3, further comprising a socket jig electrically connected to the substrate and configured to have the test object placed therein.

5. The inspection system of claim 1, wherein the specimen is a CPO module.

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