Circuit board, manufacturing method therefor, circuit board assembly and electronic device

Abstract

The embodiments of the present application relate to the technical field of electronics. Provided are a circuit board, a manufacturing method therefor, a circuit board assembly and an electronic device, which are used for measuring in real time the temperature of a position required to be measured. A thermistor is integrated into the circuit board. By means of the situation in which the resistance value of the thermistor varies with the temperature, the temperature change at the position of the thermistor is measured without any additional processing unit member. The thermistor can be flexibly arranged so as to measure in real time the temperatures of various positions to be measured. For example, if the temperature of a solder joint of a semiconductor device connected to the circuit board needs to be measured, a first conductive part coupled to the thermistor is used as a bonding pad connected to the semiconductor device, so that the temperature of the solder joint of the semiconductor device can be directly measured. For example, if the temperature at a certain position of the circuit board needs to be measured, the first conductive part coupled to the thermistor is coupled to a power supply on the circuit board, and the thermistor is arranged at the position to be measured, so that the temperature at the target position can be directly measured.

Description

Circuit boards and their manufacturing methods, circuit board assemblies, electronic devices

[0001] This application claims priority to Chinese Patent Application No. 202410504788.3, ​​filed on April 24, 2024, entitled "Circuit Board and Method for Manufacturing the Same Thereof, Circuit Board Assembly, Electronic Device", and Chinese Patent Application No. 202410983694.9, filed on July 19, 2024, entitled "Circuit Board and Method for Manufacturing the Same Thereof, Circuit Board Assembly, Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electronic technology, and in particular to a circuit board and its manufacturing method, a circuit board assembly, and an electronic device. Background Technology

[0003] With the development of electronic technology, the functions of electronic devices are becoming increasingly rich and comprehensive, and the processing power of semiconductor devices such as chips and power devices in electronic devices is constantly improving.

[0004] The generation of heat during semiconductor device operation is currently unavoidable, leading to an overall increase in the temperature around the semiconductor device. However, on the one hand, the materials of the semiconductor device, the circuit board supporting the semiconductor device, and the solder joints connecting the semiconductor device and the PCB are different, and the coefficients of thermal expansion (CTE) between these materials are often mismatched, which exacerbates solder joint fatigue creep (crack formation). Prolonged use will cause these cracks to propagate and eventually lead to failure. On the other hand, for temperature-sensitive devices, excessively high temperatures at their location will directly affect their performance.

[0005] Therefore, if the temperature at the required detection location can be detected accurately in real time, reasonable thermal management and prediction of the thermal fatigue life of the solder joint can be effectively carried out. Summary of the Invention

[0006] This application provides a circuit board and its manufacturing method, a circuit board assembly, and an electronic device for real-time and accurate detection of the temperature at the desired detection location.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] A first aspect of this application provides a circuit board including: a first conductor layer, a first dielectric layer, at least one second conductor layer, at least one second dielectric layer, and a Wheatstone bridge integrated in the first and second conductor layers. The first conductor layer includes a first conductive portion, a second conductive portion, and a third conductive portion. The first dielectric layer covers the first conductor layer, exposing the second and third conductive portions. At least one second conductor layer and at least one second dielectric layer are alternately disposed on the side of the first conductor layer away from the first dielectric layer. The Wheatstone bridge includes a first input terminal, a second input terminal, a first output terminal, a second output terminal, and a plurality of resistors; the resistors are located in the first conductor layer or the second conductor layer, and the plurality of resistors include one or more thermistors. The first and second input terminals are coupled to the first conductive portion, the first output terminal is coupled to the second conductive portion, and the second output terminal is coupled to the third conductive portion.

[0009] The circuit board provided in this application integrates a Wheatstone bridge containing a thermistor. Temperature changes at the thermistor's location are detected by observing the resistance change of the thermistor with temperature, eliminating the need for additional processing units. The Wheatstone bridge can be flexibly arranged to detect the temperature of various test locations in real time. Furthermore, the first conductive part can be used directly as a heat source to be measured or connected to a heat source to be measured, while the Wheatstone bridge is directly coupled to the first conductive part. Therefore, temperature changes on the first conductive part can be directly transmitted to the thermistor of the Wheatstone bridge, meaning the thermistor can directly sense the temperature change of the heat source to be measured, thus achieving close-range, rapid, and direct temperature detection of the heat source. For example, if it is necessary to detect the temperature of a semiconductor device solder joint connected to the circuit board, the first conductive part coupled to the Wheatstone bridge can be used as a solder pad connected to the semiconductor device solder joint. The temperature of the solder joint is directly transmitted to the thermistor, allowing direct testing of the semiconductor device solder joint temperature with a detection accuracy within ±0.5℃. Alternatively, for example, if it is necessary to detect the temperature at a certain location on a circuit board, the first conductive part is placed at the location to be measured as a heat source to be measured. The temperature of the first conductive part is directly transferred to the thermistor, and the temperature at the target location can be directly measured.

[0010] In one possible implementation, the thermistor is located in the first conductor layer. Since both the thermistor and the first conductive part are located in the first conductor layer, the distance between them can be reduced, allowing the thermistor to accurately reflect the temperature of the first conductive part, thereby improving detection accuracy.

[0011] In one possible implementation, the multiple resistors also include multiple non-thermostats located in at least one second conductor layer. By layering the thermistors and non-thermostats, the fabrication process of the Wheatstone bridge can be simplified.

[0012] In one possible implementation, at least one of the resistors included in the Wheatstone bridge is a thin-film resistor. Compared to constructing a Wheatstone bridge by welding resistor devices, constructing a Wheatstone bridge using thin-film resistors can reduce the area occupied by the Wheatstone bridge.

[0013] In one possible implementation, the first conductor layer includes a first conductive layer and a first resistive layer, the first resistive layer including a thermistor; the resistivity of the material of the first conductive layer is less than the resistivity of the material of the first resistive layer. This is a structurally simple implementation.

[0014] In one possible implementation, a first conductive layer is disposed on the surface of the first resistive layer opposite to the second dielectric layer. The first conductive layer has a first opening, and the portion of the first resistive layer corresponding to the first opening serves as a thermistor. This allows the first conductive layer and the first resistive layer to be processed simultaneously in some processes during the fabrication of the first conductive layer, simplifying the fabrication process. Furthermore, since the first resistive layer is located below the first conductive layer, it does not affect signal transmission within the first conductive layer.

[0015] In one possible implementation, the thickness of the first resistive layer is 10nm to 1000nm. Due to the limited space on the circuit board, if the first resistive layer is too thin, the resistor produced within that limited space cannot meet the detection requirements. Conversely, if the first resistive layer is too thick, it will affect the drilling quality and the thickness of the circuit board.

[0016] In one possible implementation, at least one second conductor layer includes a second conductive layer and a second resistive layer, the second resistive layer including a non-thermostat; the resistivity of the material of the second conductive layer is less than the resistivity of the material of the second resistive layer. This is a structurally simple implementation.

[0017] In one possible implementation, the second conductive layer is disposed on the surface of the second resistive layer facing the first conductive layer, and the second conductive layer has a second opening. The portion of the second resistive layer corresponding to the second opening serves as a non-thermostat. This allows the second conductive layer and the second resistive layer to be processed simultaneously in some processes during the fabrication of the second conductive layer, simplifying the fabrication process. Furthermore, since the second resistive layer is located below the second conductive layer, it will not affect signal transmission within the second conductive layer.

[0018] In one possible implementation, the thickness of the second resistive layer is 10nm to 1000nm. Due to the limited space on the circuit board, if the second resistive layer is too thin, the resistance produced within that limited space cannot meet the detection requirements. Conversely, if the second resistive layer is too thick, it will affect the drilling quality and the thickness of the circuit board.

[0019] In one possible implementation, the multiple resistors include a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor, where the fourth and sixth resistors are thermistors. One end of the first resistor is coupled to the first input terminal, and the other end is coupled to the first output terminal. One end of the second resistor is coupled to the first input terminal, and the other end is coupled to the second output terminal. One end of the third resistor is coupled to the first output terminal, and the other end is coupled to the second output terminal. One end of the fourth resistor is coupled to the first output terminal, and the other end is coupled to one end of the fifth resistor. The other end of the fifth resistor is coupled to one end of the sixth resistor, and the other end of the sixth resistor is coupled to the second output terminal. Due to low power consumption requirements, the center value of the thermistors in the Wheatstone bridge needs to be relatively large. However, due to various limitations, the center value of a single thermistor cannot be very large. But by changing the topology design of the Wheatstone bridge and setting two thermistors in series in the Wheatstone bridge, it is equivalent to including a thermistor with a relatively large center value in the Wheatstone bridge. Furthermore, since the two thermistors detect the temperature at two different locations, the Wheatstone bridge with two thermistors has fewer total resistors and occupies less space compared to a Wheatstone bridge with two single thermistors.

[0020] In one possible implementation, multiple resistors include a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor, one of which is a thermistor; one end of the seventh resistor is coupled to the first input terminal, and the other end of the seventh resistor is coupled to the first output terminal; one end of the eighth resistor is coupled to the first input terminal, and the other end of the eighth resistor is coupled to the second output terminal; one end of the ninth resistor is coupled to the first output terminal, and the other end of the ninth resistor is coupled to the second input terminal; one end of the tenth resistor is coupled to the second output terminal, and the other end of the tenth resistor is coupled to the second input terminal. This is a structurally simple implementation.

[0021] In one possible implementation, the temperature change rate of the thermistor is greater than or equal to 2Ω / ℃. Limiting the temperature change rate of the thermistor to greater than or equal to 2Ω / ℃ makes the feedback voltage output of the Wheatstone bridge easier to acquire, reducing the accuracy requirements of the acquisition equipment and lowering costs.

[0022] In one possible implementation, the sheet resistance of the thermistor is between 200Ω and 3000Ω. If the sheet resistance is too small, more wiring resources are needed to obtain the target thin-film resistance center value. If the center value of the thermistor is too small, the resistance change due to temperature variations will be relatively small, resulting in insignificant current changes that are difficult to detect and affecting the accuracy of temperature detection. If the sheet resistance is too large, it is difficult to achieve a high resistance temperature coefficient. The ratio of the resistance change due to temperature variations to the total resistance decreases, resulting in a smaller detectable voltage change and hindering the acquisition of accurate temperature change values.

[0023] In one possible implementation, the center resistance of the thermistor is between 200Ω and 3000Ω. The voltage output from the first and second output terminals of the Wheatstone bridge can reflect the resistance change of the thermistor, and the output voltage is positively correlated with the center resistance. Therefore, if the center resistance is too small, the thermistor's temperature change will be small, the current change across the thermistor will be insignificant, and the output voltage will be too small to be easily detected, affecting the accuracy of temperature detection. Conversely, if the center resistance is too large, the resistor area needs to be increased, resulting in excessive trace resources and hindering the integration of the Wheatstone bridge on the circuit board.

[0024] In one possible implementation, the distance from the thermistor to the first conductive part is 5μm-1mm. In some technologies, a thermistor is surface-mounted next to the device under test (DUT) on a circuit board to detect the temperature of the DUT. Due to the inherent characteristics of the thermistor, it needs to be at least 3mm-5mm away from the DUT to obtain accurate temperature readings. However, the thin-film resistor used in this application can read instantaneous temperature changes without being affected by drastic temperature fluctuations. Therefore, the distance from the thermistor to the first conductive part can be as small as 5μm-1mm. Thus, the solution in this application can improve detection accuracy and also achieve product miniaturization.

[0025] In one possible implementation, the circuit board also includes an eleventh resistor, which is coupled to the first input terminal. By setting an eleventh resistor in series with the Wheatstone bridge, it is equivalent to setting a pull-up resistor, which increases the series resistance of the eleventh resistor and the Wheatstone bridge, thereby reducing the power consumption of the detection circuit.

[0026] A second aspect of this application provides a circuit board assembly, including a processing unit, a circuit board, and a heat source to be tested; the circuit board includes any of the circuit boards in the first aspect; the processing unit is coupled to a second conductive part and a third conductive part respectively; the heat source to be tested is connected to a first conductive part, or the first conductive part serves as the heat source to be tested.

[0027] In one possible implementation, the circuit board assembly further includes back-end circuitry coupled to the first conductive portion. This is equivalent to the back-end circuitry being coupled in parallel with the Wheatstone bridge, which can reduce the impact of the Wheatstone bridge on the power consumption of the back-end circuitry.

[0028] In one possible implementation, the circuit board assembly also includes back-end circuitry coupled to the Wheatstone bridge on the circuit board. This is equivalent to the back-end circuitry being connected in series with the Wheatstone bridge, still allowing the temperature at the location to be measured to be obtained.

[0029] In one possible implementation, the circuit board assembly also includes an excitation source coupled to the first conductive part. This is equivalent to the back-end circuit being uncoupled from the Wheatstone bridge, while the first conductive part is coupled to the excitation source. The Wheatstone bridge can be placed at any location where temperature needs to be detected, allowing for direct and accurate measurement of the temperature at the set location.

[0030] A third aspect of this application provides a circuit board assembly, including a processing unit, a circuit board, and a heat source to be measured; the circuit board includes a first conductive portion and a second conductive portion, and a first dielectric layer, a first conductor layer, and a second dielectric layer stacked sequentially; the first conductor layer includes a thermistor coupled between the first conductive portion and the second conductive portion, and the thermistor is a thin-film resistor; the processing unit is coupled to the first conductive portion or the second conductive portion; the first conductive portion is connected to the heat source to be measured; or, the first conductive portion serves as the heat source to be measured.

[0031] The circuit board assembly provided in this application integrates a thermistor inside the circuit board. Temperature changes at the thermistor's location are detected by observing the change in its resistance with temperature, eliminating the need for additional processing units. The thermistors can be flexibly arranged to detect the temperature of various locations in real time. Furthermore, the first conductive part can be used directly as a heat source to be measured, or it can be connected to a heat source to be measured, while the thermistor is directly coupled to the first conductive part. Therefore, temperature changes on the first conductive part can be directly transmitted to the thermistor, meaning the thermistor can directly sense the temperature changes of the heat source to be measured, thereby achieving close-range, rapid, and direct temperature detection of the heat source.

[0032] In one possible implementation, the circuit board further includes a first resistor and a second conductor layer. The second conductor layer is disposed on the side of the second dielectric layer away from the first conductor layer. The first resistor is located on the second conductor layer. The first resistor and the processing unit are coupled to the same conductive portion in the first conductive portion and the second conductive portion. By setting the first resistor in series with the thermistor, it is equivalent to setting a pull-up resistor, which can increase the series resistance value of the first resistor and the thermistor, thereby reducing the power consumption of the detection circuit.

[0033] In one possible implementation, the circuit board assembly also includes a capacitor coupled in parallel with the thermistor. By incorporating the capacitor in parallel with the thermistor, a filter can be formed to improve the accuracy of temperature detection.

[0034] A fourth aspect of the present application provides an electronic device, including a circuit board assembly and a mid-frame, wherein the circuit board assembly is disposed on the mid-frame; the circuit board assembly includes the circuit board assembly of the second aspect.

[0035] A fifth aspect of this application provides a method for fabricating a circuit board, the circuit board including a Wheatstone bridge; the method for fabricating the circuit board includes: forming at least one second conductor layer and at least one second dielectric layer; the at least one second conductor layer and at least one second dielectric layer are alternately disposed; forming a first conductor layer, the first conductor layer being located on the side of the second dielectric layer away from the second conductor layer; the first conductor layer including a first conductive portion, a second conductive portion and a third conductive portion; forming a first dielectric layer, the first dielectric layer covering the first conductor layer, exposing the second conductive portion and the third conductive portion; wherein, the Wheatstone bridge includes a first input terminal, a second input terminal, a first output terminal, a second output terminal and a plurality of resistors; the resistors are located on the first conductor layer or the second conductor layer; the plurality of resistors include one or more thermistors, the first input terminal and the second input terminal are coupled to the first conductive portion, the first output terminal is coupled to the second conductive portion, and the second output terminal is coupled to the third conductive portion.

[0036] In one possible implementation, forming the first conductor layer includes: sequentially forming a first resistive film and a first conductive film on the surface of the second dielectric layer away from the second conductor layer; patterning the first conductive film and the first resistive film to form a first conductive film pattern and a first resistive layer; and patterning the first conductive film pattern to expose a portion of the first resistive layer, thereby forming the first conductive layer. This is a simple implementation method.

[0037] In one possible implementation, patterning the first conductive film and the first resistive film includes: patterning the first conductive film and the first resistive film using an exposure, development, and acid etching process.

[0038] In one possible implementation, patterning the first conductive film pattern includes: patterning the first conductive film pattern using an exposure, development, and alkaline etching process. Attached Figure Description

[0039] Figure 1 is a structural diagram of an electronic device provided in an embodiment of this application;

[0040] Figure 2 is a schematic diagram of a temperature detection scheme provided in an embodiment of this application;

[0041] Figure 3 is a schematic diagram of a PCB structure provided in an embodiment of this application;

[0042] Figures 4A and 4B are schematic diagrams of the topology of a Wheatstone bridge provided in an embodiment of this application;

[0043] Figures 5A and 5B are schematic diagrams of a PCB structure provided in an embodiment of this application;

[0044] Figures 5C and 5D are disassembled diagrams of a PCB provided in an embodiment of this application;

[0045] Figure 6A is a schematic diagram of the topology of a detection circuit in a circuit board provided in an embodiment of this application;

[0046] Figure 6B is a schematic diagram of a PCB structure provided in an embodiment of this application;

[0047] Figure 7 is a flowchart of a method for manufacturing a circuit board according to an embodiment of this application;

[0048] Figures 8A-10 are schematic diagrams illustrating the fabrication process of a circuit board according to an embodiment of this application;

[0049] Figure 11 is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0050] Figure 12 is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0051] Figure 13 is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0052] Figure 14 is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0053] Figure 15 is a schematic layout diagram of a first conductor layer provided in an embodiment of this application;

[0054] Figures 16A and 16B are schematic diagrams of a circuit board assembly provided in an embodiment of this application;

[0055] Figure 17A is a topological schematic diagram of a detection circuit provided in an embodiment of this application;

[0056] Figure 17B is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0057] Figure 18A is a topological schematic diagram of a detection circuit provided in an embodiment of this application;

[0058] Figure 18B is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0059] Figures 19A and 19B are schematic diagrams of a circuit board assembly provided in an embodiment of this application;

[0060] Figure 20A is a topological schematic diagram of a detection circuit provided in an embodiment of this application;

[0061] Figure 20B is a schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0062] Figure 21A is a topological schematic diagram of a detection circuit provided in an embodiment of this application;

[0063] Figure 21B is a schematic diagram of a circuit board assembly provided in an embodiment of this application. Detailed Implementation

[0064] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0065] Hereinafter, the terms "second," "first," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "second," "first," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0066] Furthermore, in the embodiments of this application, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly based on the orientation of the components in the accompanying drawings.

[0067] In the embodiments of this application, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled connection" can be a direct electrical connection or an indirect electrical connection through an intermediate medium. The term "contact" can be direct contact or indirect contact through an intermediate medium.

[0068] In this embodiment of the application, "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0069] This application provides an electronic device, which may be, for example, a foldable electronic device. The electronic device may be, for example, a consumer electronics product, a home electronics product, an in-vehicle electronics product, or a financial electronics product. Consumer electronics products include mobile phones, tablets, laptops, e-readers, personal computers (PCs), personal digital assistants (PDAs), desktop monitors, smart wearable products (e.g., smartwatches, smart bracelets), virtual reality (VR) electronic devices, augmented reality (AR) electronic devices, drones, etc. Home electronics products include smart door locks, televisions, refrigerators, and rechargeable small household appliances (e.g., soymilk makers, robot vacuum cleaners), etc. In-vehicle electronics products include in-vehicle navigation systems, in-vehicle DVDs, etc. Financial electronics products include ATMs, self-service electronic devices, etc.

[0070] This application does not impose any special restrictions on the specific form of the above-mentioned electronic device. For the sake of convenience, the following embodiments all use mobile phones as an example for illustration.

[0071] Figure 1 is an architecture diagram of an electronic device provided in an embodiment of this application.

[0072] Taking a mobile phone as an example of the electronic device provided in this application embodiment, as exemplarily shown in FIG1, the electronic device 1 mainly includes a display module 2, a middle frame 3, a shell (or battery cover, back cover) 4 and a cover plate 5.

[0073] The display module 2 has a light-emitting side from which the display image can be seen and a back side opposite to the light-emitting side. The back side of the display module 2 is close to the middle frame 3, and the cover plate 5 is disposed on the light-emitting side of the display module 2.

[0074] The aforementioned display module 2 includes a display panel (DP). In one possible embodiment of this application, the display module 2 is a liquid crystal display module. In this case, the display panel is a liquid crystal display (LCD). Based on this, the display module 2 also includes a backlight unit (BLU) located on the back of the LCD (away from the side of the LCD used to display images). The backlight unit can provide a light source to the LCD so that each sub-pixel in the LCD can emit light to achieve image display.

[0075] In another possible embodiment of this application, the display module 2 is an organic light-emitting diode (OLED) display module. In this case, the display screen is an organic light-emitting diode (OLED) display screen. Since each subpixel in an OLED display screen has an electroluminescent layer, the OLED display screen can achieve self-illumination after receiving an operating voltage. In this case, the display module 2 with an OLED display screen does not need to include the aforementioned backlight module.

[0076] The cover plate 5 is located on the side of the display module 2 away from the middle frame 3. The cover plate 5 can be, for example, a cover glass (CG), which can have a certain degree of toughness.

[0077] The middle frame 3 is located between the display module 2 and the housing 4. The surface of the middle frame 3 away from the display module 2 is used to mount internal components such as batteries, printed circuit boards (PCBs), cameras, and antennas. After the housing 4 is closed with the middle frame 3, the aforementioned internal components are located between the housing 4 and the middle frame 3.

[0078] The aforementioned electronic device 1 also includes semiconductor devices such as a motherboard, system on chip (SOC), power management unit (PMU), and radio frequency integrated circuit (RFIC) disposed on the PCB. The PCB is used to carry the aforementioned semiconductor devices and to complete signal interaction with the aforementioned semiconductor devices.

[0079] The generation of heat during semiconductor device operation is currently unavoidable, leading to an overall increase in the temperature around the semiconductor device. However, on the one hand, the materials of the semiconductor device, the circuit board supporting the semiconductor device, and the solder joints connecting the semiconductor device and the PCB are different, and the coefficients of thermal expansion (CTE) between these materials are often mismatched, which exacerbates solder joint fatigue creep (crack formation). Prolonged use will cause these cracks to propagate and eventually lead to failure. On the other hand, for temperature-sensitive devices, excessively high temperatures at their location will directly affect their performance. Therefore, real-time and accurate monitoring of the temperature at the required detection location allows for effective and reasonable thermal management and prediction of solder joint thermal fatigue life.

[0080] Figure 2 is a schematic diagram of a temperature detection scheme provided in an embodiment of this application.

[0081] In some technologies, as shown in Figure 2, for SOC chips, a negative temperature coefficient (NTC) circuit is set inside the SOC to detect the temperature of different areas of the silicon wafer, and the solder joint temperature of the corresponding area is calculated through steady-state thermal simulation. However, this method can only obtain the temperature of the area inside the chip where the NTC circuit is set, and the temperature of the solder joint area is calculated by software. It cannot achieve precise temperature detection of the solder joint location.

[0082] In some technologies, as shown in Figure 2, for high-power devices (such as PMUs and RFICs), the temperature of the area surrounding the high-power device is obtained by soldering NTC resistors next to the circuit and onto the PCB surface. The temperature of the solder joint cannot be directly conducted to the NTC resistor; the temperature of the area can only be measured indirectly.

[0083] Therefore, current temperature detection technology can obtain the temperature of the area near the solder joint, but cannot directly measure the temperature at the solder joint itself.

[0084] This application provides a temperature detection technology that can directly measure the real-time temperature at the solder joint.

[0085] Figure 3 is a schematic diagram of a PCB structure provided in an embodiment of this application.

[0086] This application provides a circuit board, such as a PCB. As shown in FIG3, the PCB includes a first conductor layer 10, a first dielectric layer 20, at least one second conductor layer 30, at least one second dielectric layer 40, and a Wheatstone bridge 50.

[0087] The first conductor layer 10 includes a first conductive portion 11, a second conductive portion 12, and a third conductive portion 13, which are used for coupling with external devices. This application embodiment does not limit the shape or arrangement of the first conductive portion 11, the second conductive portion 12, and the third conductive portion 13; Figure 3 is merely an illustration. The material of the first conductor layer 10 may include, for example, copper (Cu). Of course, this application embodiment does not limit the first conductor layer 10 to only include the first conductive portion 11, the second conductive portion 12, and the third conductive portion 13; the first conductor layer 10 may also include other conductive portions.

[0088] For example, the PCB is a rigid circuit board, and the first conductive part 11, the second conductive part 12 and the third conductive part 13 can all be pads. The Wheatstone bridge 50 is used to detect the heating of the solder joint at the pad position.

[0089] Alternatively, as an example, the PCB is a flexible circuit board, the first conductive part 11 can be a trace, the second conductive part 12 and the third conductive part 13 can be pads, and the Wheatstone bridge 50 is used to detect the heating status at a certain location on the trace.

[0090] The first dielectric layer 20 covers the first conductor layer 10, and the first dielectric layer 20 exposes the second conductive portion 12 and the third conductive portion 13. For example, the first dielectric layer 20 serves as the surface layer of a PCB. The first dielectric layer 20 may expose the first conductive portion 11, or it may not expose the first conductive portion 11. Figure 3 illustrates an example where the first dielectric layer 20 exposes the first conductive portion 11.

[0091] For example, the PCB is a rigid circuit board, and the material of the first dielectric layer 20 is solder resist ink.

[0092] Or, for example, the PCB is a flexible circuit board, and the material of the first dielectric layer 20 is a coverlay.

[0093] At least one second conductor layer 30 and at least one second dielectric layer 40 are alternately disposed on the side of the first conductor layer 10 away from the first dielectric layer 20. For example, the side of the first conductor layer 10 away from the first dielectric layer 20 consists of the second dielectric layer 40, the second conductor layer 30, the second dielectric layer 40, the second conductor layer 30, and the second dielectric layer 40, with the second dielectric layer 40 furthest from the first dielectric layer 20 serving as another surface layer of the PCB. This application embodiment does not limit the number of second conductor layers 30 and second dielectric layers 40 included in the PCB; Figure 3 is merely an illustration.

[0094] For example, the PCB is a rigid circuit board, and the material of the second dielectric layer 40 is a prepreg.

[0095] Or, as an example, the PCB is a flexible circuit board, and the material of the second dielectric layer 40 is polyimide (PI).

[0096] The Wheatstone bridge 50 includes a first input terminal I1, a second input terminal I2, a first output terminal O1, and a second output terminal O2. The first input terminal I1 and the second input terminal I2 are coupled to a first conductive portion 11, the first output terminal O1 is coupled to a second conductive portion 12, and the second output terminal O2 is coupled to a third conductive portion 13. The first input terminal I1, the second input terminal I2, the first output terminal O1, and the second output terminal O2 may, for example, be located in a first conductor layer 10 or a second conductor layer 30.

[0097] The structure of the Wheatstone bridge 50 in this application embodiment is not limited, and the Wheatstone bridge 50 in related technologies is applicable to the embodiments of this application.

[0098] In some embodiments, the Wheatstone bridge 50 further includes a plurality of resistors located in the first conductor layer 10 or the second conductor layer 30. For example, some of the resistors are located in the first conductor layer 10, and some of the resistors are located in the second conductor layer 30. Alternatively, all of the resistors are located in the first conductor layer 10, or all of the resistors are located in the second conductor layer 30.

[0099] Among them, multiple resistors include one or more thermistors.

[0100] A thermistor is a type of sensor resistor whose resistance changes with temperature. Based on their temperature coefficient, they are classified into positive temperature coefficient thermistors (PTC thermistors) and negative temperature coefficient thermistors (NTC thermistors). The resistance of a PTC thermistor increases with increasing temperature, while the resistance of a NTC thermistor decreases with increasing temperature. In this embodiment, the Wheatstone bridge 50 includes either a PTC or a NTC thermistor.

[0101] The Wheatstone Bridge 50 is used to find an unknown resistor very precisely by comparing it to a known resistance value. The Wheatstone Bridge 50 uses either null or balanced conditions to find the unknown resistor.

[0102] The PCB provided in this application integrates a Wheatstone bridge 50 containing a thermistor within the PCB. Temperature changes at the thermistor's location are detected by observing the resistance change of the thermistor with temperature, eliminating the need for additional processing components. The Wheatstone bridge 50 can be flexibly arranged to detect the temperature of various test locations in real time. Furthermore, the first conductive part 11 can be used directly as a heat source to be measured or connected to a heat source to be measured, while the Wheatstone bridge 50 is directly coupled to the first conductive part 11. Therefore, temperature changes on the first conductive part 11 can be directly transmitted to the thermistor of the Wheatstone bridge 50, meaning the thermistor can directly sense the temperature changes of the heat source to be measured, thus achieving close-range, rapid, and direct temperature detection of the heat source. For example, if it is necessary to detect the temperature of a semiconductor device solder joint connected to the PCB, the first conductive part 11 coupled to the Wheatstone bridge 50 can be used as a pad connected to the semiconductor device solder joint. The temperature of the solder joint is directly transmitted to the thermistor, allowing direct testing of the semiconductor device solder joint temperature with a detection accuracy within ±0.5℃. Alternatively, for example, if it is necessary to detect the temperature at a certain location on a circuit board, the first conductive part 11 is placed at the location to be measured as a heat source to be measured. The temperature of the first conductive part 11 is directly transferred to the thermistor, and the temperature at the target location can be directly measured.

[0103] In some embodiments, the temperature change rate of the thermistor is greater than or equal to 2 Ω / ℃. For example, the temperature change rate of the thermistor is 2 Ω / ℃, 3 Ω / ℃, 5 Ω / ℃, 7 Ω / ℃, 10 Ω / ℃, 13 Ω / ℃, 15 Ω / ℃, 17 Ω / ℃, or 20 Ω / ℃, etc.

[0104] For example, the resistance of a thermistor varies by one order of magnitude between 0°C and 150°C.

[0105] By limiting the temperature change rate of the thermistor to greater than or equal to 2Ω / ℃, the feedback voltage output of the Wheatstone Bridge 50 is easy to acquire, which reduces the accuracy requirements of the acquisition equipment and lowers costs. Of course, the temperature change rate of the thermistor can also be less than 2Ω / ℃.

[0106] In some embodiments, the center resistance of the thermistor in the Wheatstone bridge 50 is 200Ω to 3000Ω. For example, the center resistance of the thermistor is 200Ω, 300Ω, 500Ω, 700Ω, 1000Ω, 1300Ω, 1500Ω, 1700Ω, 2000Ω, 2300Ω, 2500Ω, 2700Ω, or 3000Ω, etc.

[0107] In some embodiments, the center resistance of the non-thermostat in the Wheatstone bridge 50 is 200Ω to 3000Ω. For example, the center resistance of the non-thermostat is 200Ω, 300Ω, 500Ω, 700Ω, 1000Ω, 1300Ω, 1500Ω, 1700Ω, 2000Ω, 2300Ω, 2500Ω, 2700Ω, or 3000Ω, etc.

[0108] The voltage output from the first output terminal O1 and the second output terminal O2 of the Wheatstone Bridge 50 can provide feedback on the resistance change of the thermistor, and the output voltage is positively correlated with the center resistance value of the thermistor. Therefore, if the center resistance value of the thermistor is too small, the change in the thermistor with temperature will be relatively small, the change in current across the thermistor will be insignificant, the output voltage will be too small to be detected, and the accuracy of temperature detection will be affected. On the other hand, if the center resistance value of the thermistor is too large, the area of ​​the resistor needs to be increased, resulting in excessive trace resources and hindering the integration of the Wheatstone Bridge 50 into the PCB.

[0109] In some embodiments, the sheet resistance of the thermistor in the Wheatstone bridge 50 is 200Ω to 3000Ω. For example, the sheet resistance of the thermistor is 200Ω, 300Ω, 500Ω, 700Ω, 1000Ω, 1300Ω, 1500Ω, 1700Ω, 2000Ω, 2300Ω, 2500Ω, 2700Ω, or 3000Ω, etc.

[0110] In some embodiments, the sheet resistance of the non-thermostat in the Wheatstone bridge 50 is 200Ω to 3000Ω. For example, the sheet resistance of the thermistor is 200Ω, 300Ω, 500Ω, 700Ω, 1000Ω, 1300Ω, 1500Ω, 1700Ω, 2000Ω, 2300Ω, 2500Ω, 2700Ω, or 3000Ω, etc.

[0111] Sheet resistance is the resistance between edges of a square thin-film conductive material. The product of sheet resistance and L / W (L: length, W: width) is the center resistance value.

[0112] If the sheet resistance of a resistor is too small, more trace resources are needed to obtain the target thin-film resistor center value. If the center value of a thermistor is too small, the resistance change of the thermistor due to temperature changes will be relatively small, and the current change on the thermistor will not be obvious, making it difficult to detect and affecting the accuracy of temperature detection. If the sheet resistance of a resistor is too large, it is difficult to achieve a high temperature coefficient of resistance (TCR). Similarly, the ratio of the resistance change due to temperature changes to the total resistance is reduced, and the detectable voltage change is smaller, which is not conducive to obtaining accurate temperature change values.

[0113] For example, taking the first conductive part 11 coupled to the SOC for testing the solder joint temperature of the SOC as an example, the SOC is soldered to the first conductive part 11 through solder joints. The trace width and spacing on the PCB are the conventional 20μm / 20μm, and the width of the resistor in the Wheatstone bridge 50 is also 20μm. To design a resistor with a center resistance of 2000Ω and a sheet resistance of 200Ω, a resistor segment with a length of 200μm is required.

[0114] Figures 4A and 4B are schematic diagrams of the topology of a Wheatstone bridge provided in an embodiment of this application.

[0115] In some embodiments, as shown in FIG4A, the Wheatstone bridge 50 includes four resistors, namely the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10.

[0116] One end of the seventh resistor R7 is coupled to the first input terminal I1, and the other end of the seventh resistor R7 is coupled to the first output terminal O1. One end of the eighth resistor R8 is coupled to the first input terminal I1, and the other end of the eighth resistor R8 is coupled to the second output terminal O2. One end of the ninth resistor R9 is coupled to the first output terminal O1, and the other end of the ninth resistor R9 is coupled to the second input terminal I2. One end of the tenth resistor R10 is coupled to the second output terminal O2, and the other end of the tenth resistor R10 is coupled to the second input terminal I2.

[0117] For example, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 include thermistors.

[0118] For example, one of the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 can be a thermistor. That is, the seventh resistor R7 can be a thermistor, and the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 can be non-thermal resistors. Alternatively, the eighth resistor R8 can be a thermistor, and the seventh resistor R7, the ninth resistor R9, and the tenth resistor R10 can be non-thermal resistors. Alternatively, the ninth resistor R9 can be a thermistor, and the seventh resistor R7, the eighth resistor R8, and the tenth resistor R10 can be non-thermal resistors. Alternatively, the tenth resistor R10 can be a thermistor, and the seventh resistor R7, the eighth resistor R8, and the ninth resistor R9 can be non-thermal resistors.

[0119] Alternatively, for example, multiple resistors among the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 can be thermistors. That is, the seventh resistor R7 and the eighth resistor R8 can be thermistors, and the ninth resistor R9 and the tenth resistor R10 can be non-thermostats. Alternatively, the ninth resistor R9 and the tenth resistor R10 can be thermistors, and the seventh resistor R7 and the eighth resistor R8 can be non-thermostats, and so on.

[0120] In some embodiments, the center resistance of the seventh resistor R7 is equal to the center resistance of the eighth resistor R8, the center resistance of the ninth resistor R9 is equal to the center resistance of the tenth resistor R10, and the center resistance of the seventh resistor R7 is not equal to the center resistance of the ninth resistor R9.

[0121] In the Wheatstone bridge 50 shown in Figure 4A, the null or balanced conditions are used to find the unknown resistor. The seventh resistor R7 is a thermistor. Since R7*R in the Wheatstone bridge 50... 10 =R9*R8, therefore, when there is no temperature change, R7*R 10 -R9*R8=0,U 12-13 / U 11 =(R7*R 10 -R9*R8) / [(R7+R9)*(R 10 +R8)], Wheatstone bridge 50 output U 12-13 =0. When the temperature changes, the resistance of the thermistor changes, R7′*R 10 -R9*R8≠0U 12-13 / U 11 =(R7′*R 10 -R9*R8) / [(R7′+R9)*(R 10 +R8)], Wheatstone bridge 50 output U 12-13 ≠0. With the resistance values ​​of the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 fixed, through U... 12-13 The change in the resistance (R7′) of the thermistor R7 can be obtained. Furthermore, the temperature change can be obtained by analyzing the temperature change rate of the thermistor.

[0122] Where R7 is the resistance of the seventh resistor R7 when there is no temperature change, R7′ is the resistance of the seventh resistor R7 when the temperature changes, R8 is the resistance of the eighth resistor R8, R9 is the resistance of the ninth resistor R9, R 10 U is the resistance value of the tenth resistor R10. 11 U is the voltage at the first conductive part 11. 12-13 This is the output voltage of the Wheatstone bridge 50.

[0123] In other embodiments, the center resistance values ​​of the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 are equal. This simplifies the design and fabrication process.

[0124] Regarding the structure of the Wheatstone bridge 50, in some other embodiments, as shown in FIG4B, the Wheatstone bridge 50 includes six resistors, namely the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6.

[0125] One end of the first resistor R1 is coupled to the first input terminal I1, and the other end of the first resistor R1 is coupled to the first output terminal O1. One end of the second resistor R2 is coupled to the first input terminal I1, and the other end of the second resistor R2 is coupled to the second output terminal O2. One end of the third resistor R3 is coupled to the first output terminal O1, and the other end of the third resistor R3 is coupled to the second output terminal O2. One end of the fourth resistor R4 is coupled to the first output terminal O1, and the other end of the fourth resistor R4 is coupled to one end of the fifth resistor R5. The other end of the fifth resistor R5 is coupled to one end of the sixth resistor R6, and the other end of the sixth resistor R6 is coupled to the second output terminal O2.

[0126] For example, in the Wheatstone bridge 50 shown in Figure 4B, the fourth resistor R4 and the sixth resistor R6 are thermistors, while the other resistors are non-thermostats. The fourth resistor R4 and the sixth resistor R6 are coupled to the reference ground terminal to form a return loop.

[0127] Due to low power consumption requirements, the thermistors in the Wheatstone bridge 50 need to have a relatively large center value. However, due to various limitations, the center value of a single thermistor cannot be very large. But by using the topology design shown in Figure 4B, placing two thermistors in the Wheatstone bridge 50 is equivalent to including one thermistor with a relatively large center value in the Wheatstone bridge 50. Furthermore, since the two thermistors detect the temperature at two different locations, the Wheatstone bridge shown in Figure 4B has fewer resistors and occupies less area compared to using two Wheatstone bridges 50 as shown in Figure 4A. Additionally, by adding the fifth resistor R5, excessive voltage drop in the Wheatstone bridge 50 can be prevented. By adding the third resistor R3, the temperature change rate of the fourth resistor R4 and the sixth resistor R6 can be amplified, thereby improving detection accuracy.

[0128] In some embodiments, the Wheatstone bridge 50 may also exclude the fifth resistor R5, and the fourth resistor R4 and the sixth resistor R6 may be directly coupled in series.

[0129] In some other embodiments, the Wheatstone bridge 50 may also exclude the third resistor R3, and the third resistor R3 is not coupled between the first output terminal O1 and the second output terminal O2.

[0130] Of course, the above is merely an exemplary enumeration of the structure of the Wheatstone bridge 50 provided in the embodiments of this application, and does not constitute a limitation on the embodiments of this application.

[0131] Figure 5A is a schematic diagram of a PCB structure provided in an embodiment of this application.

[0132] In some embodiments, as shown in FIG5A, among the plurality of resistors included in the Wheatstone bridge 50, the thermistor is located in the first conductor layer 10. FIG5A illustrates the structure of the Wheatstone bridge 50 as shown in FIG4A, with the thermistor being the seventh resistor R7 as an example.

[0133] The thermistor is located in the first conductor layer 10, and the first conductive part 11 is also located in the first conductor layer 10. This can bring the thermistor and the first conductive part 11 closer together, so that the thermistor can accurately reflect the temperature of the first conductive part 11, thereby improving the detection accuracy.

[0134] For example, the distance from the thermistor to the first conductive part 11 is 5μm-1mm. For example, the distance from the end of the thermistor (seventh resistor R7) near the first conductive part 11 to the end of the first conductive part 11 near the thermistor is 5μm, 10μm, 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1mm, etc.

[0135] In some technologies, a thermistor is surface-mounted next to the device under test (DUT) on a circuit board to detect the temperature of the DUT. Due to the inherent characteristics of the thermistor, it needs to be at least 3mm to 5mm away from the DUT to obtain accurate temperature readings. However, the thin-film resistor used in this application can read instantaneous temperature changes without being affected by drastic temperature fluctuations. Therefore, the distance between the thermistor and the first conductive part 11 can be as small as 5μm to 1mm. Thus, the solution in this application improves detection accuracy and also achieves product miniaturization.

[0136] In other embodiments, as shown in FIG5B, the thermistor may also be located in the second conductor layer 30 among the multiple resistors included in the Wheatstone bridge 50.

[0137] Of course, the thermistor can be located in any of the second conductor layers 30. The thermistor can be placed in the same layer as the non-thermal resistor, or it can be placed in a different layer. This application does not limit the placement of the thermistor and non-thermal resistor in the Wheatstone bridge 50; the placement method described herein is merely illustrative.

[0138] In some embodiments, as shown in FIG5A, the Wheatstone bridge 50 includes a plurality of resistors, of which a plurality of non-thermal resistors are located in the second conductor layer 30.

[0139] Multiple non-thermal resistors can be located in the same second conductor layer 30, or multiple non-thermal resistors can be located in different second conductor layers 30. In this case, the PCB includes multiple second conductor layers 30.

[0140] Since the materials of thermistors and non-thermostats are different, the manufacturing process can be simplified by separating the non-thermostats and thermistors into layers.

[0141] Figures 5C and 5D are disassembly diagrams of a PCB provided in an embodiment of this application.

[0142] Taking the Wheatstone bridge shown in Figure 4A as an example, the layout of the seventh resistor R7, the first conductive part 11, the second conductive part 12, and the third conductive part 13 on the first conductor layer 10 can be as shown in Figure 5C. In some embodiments, the second input terminal I2 is also coupled to the reference ground terminal GND to form a return loop. The layout of the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 on the second conductor layer 30 can be as shown in Figure 5D. The first via in the first conductor layer 10 and the first via in the second conductor layer 30 are connected through the first via; the second via in the first conductor layer 10 and the second via in the second conductor layer 30 are connected through the second via; the third via in the first conductor layer 10 and the third via in the second conductor layer 30 are connected through the third via; and the fourth via in the first conductor layer 10 and the fourth via in the second conductor layer 30 are connected through the fourth via. The first via, the second via, the third via, and the fourth via penetrate the second dielectric layer 40 between the first conductor layer 10 and the second conductor layer 30.

[0143] In this embodiment, the placement of the multiple resistors in the Wheatstone bridge 50 is not limited, as long as the connection relationship shown in Figures 4A and 4B is achieved.

[0144] Figure 6A is a topological schematic diagram of a detection circuit in a circuit board provided in an embodiment of this application, and Figure 6B is a structural schematic diagram of a PCB provided in an embodiment of this application.

[0145] In some embodiments, as shown in FIG6A, the PCB further includes an eleventh resistor R11, which is coupled to the first input terminal I1 of the Wheatstone bridge 50. For example, the PCB further includes a fourth conductive portion 14, and the eleventh resistor R11 is coupled between the fourth conductive portion 14 and the first input terminal I1.

[0146] For example, as shown in Figure 6B, the eleventh resistor R11 is a thin-film resistor. For instance, the eleventh resistor R11 can be placed on the same layer as the non-thermal resistor in the Wheatstone bridge 50. Of course, the eleventh resistor R11 can also be placed on a different layer than the non-thermal resistor in the Wheatstone bridge 50; Figure 6B is merely an illustration.

[0147] By setting an eleventh resistor R11 connected in series with the Wheatstone bridge 50, it is equivalent to setting a pull-up resistor, which can increase the series resistance value of the eleventh resistor R11 and the Wheatstone bridge 50, thereby reducing the power consumption of the detection circuit.

[0148] The structure of the first conductor layer 10 and the second conductor layer 30 in the PCB will be illustrated below with reference to the PCB fabrication method provided in the embodiments of this application.

[0149] Figure 7 is a flowchart of a circuit board fabrication method provided in an embodiment of this application, and Figures 8A-10 are schematic diagrams of a circuit board fabrication process provided in an embodiment of this application.

[0150] This application embodiment also provides a method for manufacturing a circuit board, as shown in FIG7. The method for manufacturing a circuit board includes:

[0151] S10, as shown in Figures 8A-8D, at least one second conductor layer 30 and at least one second dielectric layer 40 are formed. The at least one second conductor layer 30 and at least one second dielectric layer 40 are alternately arranged.

[0152] For example, step S10 includes:

[0153] S11. Forming the second dielectric layer 40. This application embodiment does not limit the method of forming the second dielectric layer 40; for example, the second dielectric layer 40 can be formed by a vapor deposition process.

[0154] S12, Form the second conductor layer 30.

[0155] Depending on the PCB structure, steps S11 and S12 can be executed once or multiple times.

[0156] For example, when steps S11 and S12 are executed multiple times in a loop, at least one step S12 specifically includes:

[0157] S121. As shown in Figure 8A, a second resistive film 31' and a second conductive film 32' are sequentially formed on the surface of the second dielectric layer 40.

[0158] For example, a sputtering process can be used to form the second resistive film 31'. The material of the second resistive film 31' includes, for example, a mixed metal, to form a robust resistive film on the surface of the second dielectric layer 40. The material of the second resistive film 31' includes, for example, a nickel-chromium mixed metal. A vapor deposition process can be used to form the second conductive film 32', and the material of the second conductive film 32' includes, for example, copper (Cu).

[0159] S122. As shown in Figure 8B, the second resistive film 31' and the second conductive film 32' are patterned to form the second conductive film pattern 32″ and the second resistive layer 31.

[0160] For example, a wet etching process is used to pattern the second resistive film 31' and the second conductive film 32'.

[0161] For example, a photoresist is formed on the surface of the second conductive film 32', covering the second conductive film 32'. The second resistive film 31' and the second conductive film 32' are patterned using an exposure, development, and acid etching process. The photoresist is retained where the circuitry needs to be preserved, and removed from the unwanted areas, revealing the second resistive film 31' and the second conductive film 32' to be etched. An acid etching solution is used to remove the portions of the second resistive film 31' and the second conductive film 32' not covered by the photoresist, leaving the portions covered by the photoresist. An organic or alkaline stripping solution is used to remove the photoresist, exposing the retained second resistive film 31' and the second conductive film 32'. The retained portion of the second resistive film 31' serves as the second resistive layer 31 in the second conductor layer 30, and the retained portion of the second conductive film 32' serves as the second conductive film pattern 32″, which requires further processing.

[0162] S123. As shown in Figure 8C, the second conductive film pattern 32″ is patterned to expose part of the second resistive layer 31, forming the second conductive layer 32.

[0163] For example, a wet etching process is used to pattern the second conductive film pattern 32″ to form a second conductive layer 32. The second conductive layer 32 includes a second opening that exposes the second resistive layer 31. The portion of the second resistive layer 31 corresponding to the second opening (exposed) serves as a non-thermal resistor, and the portion of the second resistive layer 31 covered by the second conductive layer 32 is not used as a resistor in the Wheatstone bridge 50.

[0164] For example, a dry film is formed on the surface of the second conductive film pattern 32″, covering the second conductive film pattern 32″. The second conductive film pattern 32″ is patterned using an exposure, development, and alkaline etching process. The dry film at the locations where resistors are to be formed (e.g., the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10) is removed, while the dry film at other locations is retained, revealing the second conductive film pattern 32″ to be etched. An alkaline etching solution is used to remove the portions of the second conductive film pattern 32″ not covered by the dry film, leaving the portions covered by the dry film. The retained portions of the second conductive film pattern 32″ serve as the second conductive layer 32 in the second conductor layer 30. The second resistive layer 31 is not etched by the alkaline etching solution. The portions of the second resistive layer 31 covered by the second conductive layer 32 are used as conductors, and the portions of the second resistive layer 31 exposed by the second conductive layer 32 serve as resistors in the Wheatstone bridge 50. Alkaline etching solutions can be, for example, a combination of copper chloride (CuCl2) + hydrochloride (HCl) + hydrogen peroxide (H2O2) + water (H2O).

[0165] The PCB provided in this embodiment, as shown in FIG8C, has a structure with at least one second conductor layer 30, including a second conductive layer 32 and a second resistive layer 31. The second resistive layer 31 includes non-thermal resistors (e.g., the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10). The thermistors and non-thermal resistors are made of different materials; therefore, separating the thermistors and non-thermal resistors into layers simplifies the fabrication process.

[0166] In some embodiments, the second conductive layer 32 is disposed on the surface of the second resistive layer 31 facing away from the second dielectric layer 40 (towards the surface of the first conductor layer 10). The second conductive layer 32 has a second opening, and the portion of the second resistive layer 31 corresponding to the second opening serves as a non-thermostat. The overlapping portion of the second conductive layer 32 and the first resistive layer 101 serves as the conductive layer of the second conductor layer 30. Thus, during the fabrication of the second conductor layer 30, the second conductive layer 32 and the second resistive layer 31 can be processed simultaneously in some processes, simplifying the fabrication process.

[0167] In some embodiments, the resistivity of the material of the second conductive layer 32 is less than the resistivity of the material of the second resistive layer 31. Therefore, the conductivity of the material of the first conductive layer 102 is greater than the resistivity of the material of the first resistive layer 101. Thus, the first resistive layer 101 being located below the first conductive layer 102 will not affect the signal transmission in the first conductive layer 102.

[0168] In some embodiments, the thickness of the second resistive layer 31 is 10nm to 1000nm. For example, the thickness of the second resistive layer 31 is 10nm, 30nm, 50nm, 70nm, 100nm, 130nm, 150nm, 170nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc.

[0169] Due to the limited space in the PCB, if the second resistor layer 31 is too thin, the resistor produced within the limited space cannot meet the testing requirements. However, if the second resistor layer 31 is too thick, it will affect the drilling quality and the thickness of the circuit board.

[0170] Alternatively, for example, when steps S11 and S12 are executed multiple times in a loop, at least one step S12 specifically includes:

[0171] S121. A second conductive film 32' is formed on the surface of the second dielectric layer 40.

[0172] S122, The second conductive film 32' is patterned to form a second conductive layer (with a wiring pattern). That is, the second conductor layer 30 only includes the second conductive layer and no longer includes the second resistive layer.

[0173] The PCB provided in this application embodiment, as shown in FIG8C, may also have a structure with at least one second conductor layer 30, which includes only the second wire layer 32 and does not include the second resistor layer 31. That is, the second conductor layer 30 does not integrate the resistor in the Wheatstone bridge 50.

[0174] S13. As shown in Figure 8D, a second dielectric layer 40 is formed, which covers the second conductor layer 30.

[0175] S20, as shown in Figures 9A-9C, a first conductor layer 10 is formed. The first conductor layer 10 is located on the side of the second dielectric layer 40 away from the second conductor layer 30. The first conductor layer 10 includes a first conductive portion 11, a second conductive portion 12, and a third conductive portion 13.

[0176] For example, step S20 includes:

[0177] S21. As shown in Figure 9A, a first resistive film 101' and a first conductive film 102' are sequentially formed on the surface of the second dielectric layer 40 formed in the last step of step S10, away from the second conductor layer 30.

[0178] For example, by doping temperature-sensitive semiconductor compounds into the materials used in conventional thin-film resistors, temperature-sensitive thin-film resistor layers can be obtained.

[0179] S22. As shown in Figure 9B, the first resistive film 101' and the first conductive film 102' are patterned to form the first conductive film pattern 102″ and the first resistive layer 101.

[0180] For example, a wet etching process is used to pattern the first conductive film 102' and the first resistive film 101' to form a first conductive layer 102. The first conductive layer 102 includes a first opening that exposes the first resistive layer 101. The portion of the first resistive layer 101 corresponding to the first opening (exposed) serves as a thermistor, while the portion of the first resistive layer 101 covered by the first conductive layer 102 is not used as a resistor in the Wheatstone bridge 50.

[0181] For example, the first conductive film 102' and the first resistive film 101' are patterned using exposure, development, and acid etching processes.

[0182] First, a dry film is formed on the surface of the first conductive film 102', covering the first conductive film 102'. The first conductive film 102' and the first resistive film 101' are patterned using an exposure, development, and acid etching process. The dry film is then retained at the locations where the circuitry needs to be preserved, and removed at the locations where it is not needed, revealing the first conductive film 102' and the first resistive film 101' to be etched. Then, an acid etching solution is used to remove the portions of the first conductive film 102' and the first resistive film 101' not covered by the dry film, leaving the portions covered by the dry film. The portion retained in the first resistive film 101' serves as the first resistive layer 101 in the first conductor layer 10, and the portion retained in the first conductive film 102' serves as the first conductive film pattern 102″, which requires further processing.

[0183] S23. As shown in Figure 9C, the first conductive film pattern 102″ is patterned to expose part of the first resistive layer 101, forming the first conductive layer 102.

[0184] For example, a wet etching process is used to pattern the first conductive film pattern 102″.

[0185] For example, the first conductive film pattern 102″ is patterned using exposure, development, and alkaline etching processes.

[0186] For example, after performing step S22, the dry film covering the surface of the first conductive film pattern 102″ is removed, and a new dry film covering the first conductive film pattern 102″ and the second dielectric layer 40 is formed. The dry film at the location where the resistor (e.g., the seventh resistor R7) is to be formed is removed, while the dry film at other locations is retained, revealing the first conductive film pattern 102″ to be etched. Then, an alkaline etching solution is used to remove the portion of the first conductive film pattern 102″ not covered by the dry film, leaving the portion covered by the dry film. The retained portion of the first conductive film pattern 102″ serves as the first conductive layer 102 in the first conductor layer 10. The first resistive layer 101 is not etched by the alkaline etching solution. The portion of the first resistive layer 101 covered by the first conductive layer 102 is used as a conductor, and the portion of the first resistive layer 101 exposed by the first conductive layer 102 serves as a resistor in the Wheatstone bridge 50. Finally, an organic or alkaline stripping solution is used to remove the dry film, exposing the retained first conductive layer 102 and first resistive layer 101.

[0187] In some embodiments, the thickness of the first resistive layer 101 is 10nm to 1000nm. For example, the thickness of the first resistive layer 101 is 10nm, 30nm, 50nm, 70nm, 100nm, 130nm, 150nm, 170nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc.

[0188] Due to the limited space in the PCB, if the thickness of the first resistor layer 101 is too thin, the resistor produced within the limited space cannot meet the testing requirements. However, if the thickness of the first resistor layer 101 is too thick, it will affect the drilling quality and the thickness of the circuit board.

[0189] The PCB provided in this application embodiment includes a first conductor layer 10 comprising a first conductive layer 102 and a first resistive layer 101, wherein the first resistive layer 101 includes a thermistor. By placing the thermistor in the Wheatstone bridge 50 and the first conductive part 11 in the PCB on the same layer, the thermistor and the first conductive part 11 can be placed in close proximity, thereby improving the accuracy of the temperature feedback from the thermistor.

[0190] In some embodiments, a first conductive layer 102 is disposed on the surface of the first resistive layer 101 facing away from the second dielectric layer 40 (towards the first dielectric layer 20). The first conductive layer 102 has a first opening, and the portion of the first resistive layer 101 corresponding to the first opening serves as a thermistor. The portion of the first resistive layer 101 exposed by the first conductive layer 102 serves as a resistor, and the overlapping portion of the second conductive layer 32 and the first resistive layer 101 serves as a conductor of the second conductor layer 30. Thus, during the fabrication of the first conductor layer 10, the first conductive layer 102 and the first resistive layer 101 can be processed simultaneously in some processes, simplifying the fabrication process.

[0191] In some embodiments, the resistivity of the material of the first conductive layer 102 is less than the resistivity of the material of the first resistive layer 101. Therefore, the conductivity of the material of the first conductive layer 102 is greater than the resistivity of the material of the first resistive layer 101. Thus, the first resistive layer 101 being located below the first conductive layer 102 will not affect the signal transmission in the first conductive layer 102.

[0192] If the circuit board also includes an eleventh resistor R11, the fabrication process of the eleventh resistor R11 can be the same as that of the thermistor in the Wheatstone bridge 50. The only difference is that the eleventh resistor R11 is fabricated using a non-thermostat thin film.

[0193] S30, as shown in FIG10, a first dielectric layer 20 is formed, which covers the first conductor layer 10 and exposes the first conductive part 11, the second conductive part 12 and the third conductive part 13.

[0194] A Wheatstone bridge 50 is integrated in the first conductor layer 10 and the second conductor layer 30. By designing the shape of the first resistor layer 101 exposed by the first conductor layer 102 and the shape of the second resistor layer 31 exposed by the second conductor layer 32, the structure of the resistor in the Wheatstone bridge 50 is designed. The connection between the resistors and the connection between the resistors and the first conductive part 11, the second conductive part 12 and the third conductive part 13 are realized by the pattern of the first conductor layer 102 and the second conductor layer 32.

[0195] In some embodiments, at least one of the resistors included in the Wheatstone bridge 50 is a thin-film resistor. This reduces the area occupied by the Wheatstone bridge 50.

[0196] Figure 11 is a schematic diagram of a circuit board assembly provided in an embodiment of this application.

[0197] This application embodiment also provides a circuit board assembly, which can be disposed on the mid-frame of the electronic device provided in this application embodiment. As shown in FIG11, the circuit board assembly includes a processing unit and a PCB. The PCB includes any of the above-described PCBs, and the processing unit is coupled to the second conductive part 12 and the third conductive part 13 in the PCB respectively.

[0198] The voltage measured by the Wheatstone bridge 50 for temperature feedback is transmitted to the processing unit, which processes the voltage to obtain the temperature at the location of the first conductive part 11. The processing unit may include, for example, a microcontroller unit (MCU), which uses redundant channels of the existing MCU on the circuit board to detect voltage changes in the Wheatstone bridge 50, thereby obtaining resistance changes and ultimately temperature changes.

[0199] The circuit board assembly also includes a heat source to be measured, which can be connected to the first conductive part 11, or the first conductive part 11 can be used directly as the heat source to be measured. In this way, the Wheatstone bridge 50 is directly connected to the heat source to be measured, and the temperature change can be measured quickly and accurately.

[0200] Figure 12 is a schematic diagram of a circuit board assembly provided in an embodiment of this application.

[0201] In some embodiments, for example, the first dielectric layer 20 exposes the first conductive portion 11, the heat source to be measured can be connected to the first conductive portion 11, and the Wheatstone bridge 50 measures the temperature change of the heat source to be measured through the first conductive portion 11.

[0202] For example, as shown in Figure 12, the circuit board assembly also includes semiconductor devices connected to the first conductive part 11. The solder joints of the semiconductor devices serve as the heat source to be tested and are directly connected to the first conductive part 11. Semiconductor devices may include, for example, chips such as SOCs, RFICs, and PMUs, or power devices or battery protection boards.

[0203] In some embodiments, the circuit board assembly further includes back-end circuitry coupled to the Wheatstone bridge 50 of the circuit board.

[0204] The back-end circuit can be, for example, a reference ground voltage terminal or other semiconductor devices. This is equivalent to the Wheatstone bridge 50 being coupled between the semiconductor device and the normal back-end circuit, allowing the measurement of the temperature at the solder joint corresponding to the first conductive part 11. Alternatively, it can be understood that the Wheatstone bridge 50 is coupled in series with the back-end circuit.

[0205] Figure 13 is a schematic diagram of a circuit board assembly provided in an embodiment of this application.

[0206] In some embodiments, as shown in FIG13, the circuit board assembly further includes a back-end circuit coupled to the first conductive portion 11.

[0207] This is equivalent to both the semiconductor device and the normal back-end circuit being coupled to the first conductive part 11, allowing the temperature at the corresponding solder joint of the first conductive part 11 to be measured. Alternatively, it can be understood that the Wheatstone bridge 50 is coupled in parallel with the back-end circuit, which can reduce the power loss of the Wheatstone bridge 50 to the back-end circuit.

[0208] Figure 14 is a schematic diagram of a circuit board assembly provided in an embodiment of this application.

[0209] In some embodiments, the first conductive part 11 serves as a heat source to be measured, and the Wheatstone bridge 50 measures the temperature change of the first conductive part 11. In this case, the first conductive part 11 can be, for example, a section of a signal line, a solder pad, etc.

[0210] For example, as shown in Figure 14, the first dielectric layer 20 exposes the first conductive portion 11. The circuit board assembly also includes an excitation source coupled to the first conductive portion 11. The excitation source may be, for example, an input power supply on the circuit board, and is used to provide a signal source to the Wheatstone bridge 50. The circuit board assembly also includes back-end circuitry and semiconductor devices, neither of which are coupled to the first conductive portion 11.

[0211] This effectively integrates a Wheatstone bridge 50 as a temperature detection circuit onto the circuit board. By placing the Wheatstone bridge 50 at the location where the temperature is to be measured, the temperature at that location can be obtained.

[0212] For example, a Wheatstone bridge 50 can be placed next to the pad under test (DUT) of a chip or heat-generating device. In this case, the Wheatstone bridge 50 is not directly electrically connected to the DUT; instead, temperature is conducted to the thermistor via a dielectric medium, enabling temperature monitoring. Because the Wheatstone bridge 50 itself has a certain resistance, it will have a series voltage divider effect. Therefore, since the Wheatstone bridge 50 is not electrically connected to the DUT, it will not divert power from the back-end circuitry that is normally coupled to the DUT.

[0213] Alternatively, for example, if a temperature-sensitive device is located on the circuit board, excessively high temperatures can cause it to malfunction. Placing the Wheatstone bridge 50 near the temperature-sensitive device allows for timely temperature detection at that location and adaptive adjustments to prevent damage to the device.

[0214] Alternatively, for example, the first dielectric layer 20 does not expose the first conductive portion 11, which is a segment of the signal line, and the temperature of the signal line is directly measured.

[0215] Figure 15 is a schematic diagram of a first conductor layer provided in an embodiment of this application.

[0216] As shown in Figure 15, the first conductor layer 10 also includes a semiconductor device pad for coupling with a semiconductor device. The semiconductor device pad serves as the pad to be tested, and the first conductive portion 11 is placed next to the semiconductor device pad.

[0217] Figures 16A and 16B are schematic diagrams of the structure of a circuit board assembly provided in an embodiment of this application.

[0218] This embodiment also provides a circuit board assembly, as shown in FIG16A, which includes a processing unit, a circuit board, and a heat source to be tested.

[0219] The circuit board includes a first conductive part 11 and a second conductive part 12, as well as a first dielectric layer 20, a first conductor layer 10 and a second dielectric layer 40 stacked sequentially.

[0220] The first conductor layer 10 includes a thermistor NTC, which is coupled between the first conductive part 11 and the second conductive part 12. The thermistor NTC is a thin film resistor.

[0221] The processing unit is coupled to the second conductive part 12, as shown in FIG16A. The first dielectric layer 20 exposes the first conductive part 11, and the heat source to be tested is coupled to the first conductive part 11. Alternatively, as shown in FIG16B, the first conductive part 11 serves as the heat source to be tested, and the first dielectric layer 20 may not expose the first conductive part 11.

[0222] The circuit board assembly provided in this application integrates a thermistor NTC inside the circuit board. Temperature changes at the location of the thermistor NTC are detected by observing the change in its resistance with temperature, eliminating the need for additional processing units. The thermistor NTC can be flexibly arranged to detect the temperature of various locations in real time. Furthermore, the first conductive part 11 can be used directly as a heat source to be measured or connected to a heat source to be measured, while the thermistor NTC is directly coupled to the first conductive part 11. Therefore, temperature changes on the first conductive part 11 can be directly transmitted to the thermistor NTC, meaning the thermistor NTC can directly sense the temperature changes of the heat source to be measured, thereby achieving close-range, rapid, and direct temperature detection of the heat source to be measured.

[0223] Figure 17A is a topological schematic diagram of a detection circuit provided in an embodiment of this application, and Figure 17B is a structural schematic diagram of a circuit board assembly provided in an embodiment of this application.

[0224] In some embodiments, as shown in FIG17A, the PCB further includes a first resistor R1. The first resistor R1 and the processing unit are coupled to the same conductive portion of the first conductive portion 11 and the second conductive portion 12. Thus, the first resistor R1 is coupled to the second conductive portion 12 to achieve series connection between the first resistor R1 and the thermistor NTC. For example, the PCB further includes a third conductive portion 13, and the first resistor R1 is coupled between the third conductive portion 13 and the second conductive portion 12. The processing unit may be, for example, an MCU.

[0225] For example, as shown in Figure 17B, the PCB includes multiple layers of second dielectric layers 40 and second conductor layers 30. The second conductor layers 30 are disposed between adjacent second dielectric layers 40 (on the side of the second dielectric layer 40 away from the first conductor layer 10). The second conductor layer 30 includes a first resistor R1. The second conductor layer 30 can be disposed closer to the processing unit relative to the first conductor layer 10, or it can be disposed farther away from the processing unit relative to the first conductor layer 10. This embodiment is only an illustration.

[0226] By setting a first resistor R1 connected in series with the thermistor NTC, it is equivalent to setting a pull-up resistor, which can increase the series resistance of the first resistor R1 and the thermistor NTC, thereby reducing the power consumption of the detection circuit.

[0227] Figure 18A is a topology diagram of a detection circuit provided in an embodiment of this application, and Figure 18B is a structural diagram of a circuit board assembly provided in an embodiment of this application.

[0228] In some embodiments, as shown in FIG18A, the circuit board assembly further includes a capacitor C, which is coupled in parallel with a thermistor NTC. The integration method of the capacitor C on the PCB is not limited in the embodiments of this application. The capacitor C can be a surface-mount capacitor or a film capacitor.

[0229] As shown in Figure 18B, the integration method of capacitor C in the PCB is not limited in this embodiment of the application, as long as capacitor C and the thermistor NTC are connected in parallel.

[0230] A filter can be constructed by setting a capacitor C in parallel with the thermistor NTC to improve the accuracy of temperature detection.

[0231] Figures 19A and 19B are schematic diagrams of the structure of a circuit board assembly provided in an embodiment of this application.

[0232] This embodiment also provides a circuit board assembly, as shown in Figures 19A and 19B, which includes a processing unit, a circuit board, and a heat source to be tested.

[0233] The circuit board includes a first conductive portion 11' and a second conductive portion 12', as well as a first dielectric layer 20, a first conductor layer 10, and a second dielectric layer 40 stacked sequentially. The main difference from Figures 16A and 16B is that the processing unit is coupled to the first conductive portion 11', but no longer coupled to the second conductive portion 12'. The effect is the same as that of the circuit board assembly shown in Figures 16A and 16B, and will not be described further here.

[0234] Figure 20A is a topology diagram of a detection circuit provided in an embodiment of this application, and Figure 20B is a structural diagram of a circuit board assembly provided in an embodiment of this application.

[0235] In some embodiments, as shown in FIG20A, the PCB further includes a first resistor R1. The first resistor R1 and the processing unit are coupled to the same conductive portion of the first conductive portion 11' and the second conductive portion 12'. Thus, the processing unit is coupled to the first conductive portion 11', and the first resistor R1 is coupled to the first conductive portion 11', thereby realizing the series connection of the first resistor R1 and the thermistor NTC.

[0236] For example, as shown in Figure 20B, the PCB includes multiple layers of second dielectric layer 40 and second conductor layer 30. The second conductor layer 30 is disposed between adjacent second dielectric layers 40 (on the side of the second dielectric layer 40 away from the first conductor layer 10). The second conductor layer 30 includes a first resistor R1, which is coupled between a second conductive portion 12' and a third conductive portion 13'.

[0237] Figure 21A is a topological schematic diagram of a detection circuit provided in an embodiment of this application, and Figure 21B is a structural schematic diagram of a circuit board assembly provided in an embodiment of this application.

[0238] In some embodiments, as shown in FIG21A, the circuit board assembly further includes a capacitor C, which is coupled in parallel with a thermistor NTC.

[0239] As shown in Figure 21B, the integration method of capacitor C in the PCB is not limited in this embodiment of the application, as long as capacitor C and the thermistor NTC are connected in parallel.

[0240] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A circuit board, characterized in that, include: The first conductor layer includes a first conductive portion, a second conductive portion, and a third conductive portion; A first dielectric layer covers the first conductor layer, exposing the second conductive portion and the third conductive portion; The system comprises at least one second conductor layer and at least one second dielectric layer; the at least one second conductor layer and the at least one second dielectric layer are alternately disposed on the side of the first conductor layer away from the first dielectric layer. A Wheatstone bridge includes a first input terminal, a second input terminal, a first output terminal, a second output terminal, and multiple resistors; The resistor is located in the first conductor layer or the second conductor layer, and the plurality of resistors include one or more thermistors; the first input terminal and the second input terminal are coupled to the first conductive part, the first output terminal is coupled to the second conductive part, and the second output terminal is coupled to the third conductive part.

2. The circuit board according to claim 1, characterized in that, The thermistor is located in the first conductor layer.

3. The circuit board according to claim 1 or 2, characterized in that, The plurality of resistors also includes a plurality of non-thermal resistors located in the second conductor layer.

4. The circuit board according to any one of claims 1-3, characterized in that, At least one of the plurality of resistors is a thin-film resistor.

5. The circuit board according to any one of claims 1-4, characterized in that, The first conductor layer includes a first wire layer and a first resistive layer, wherein the first resistive layer includes the thermistor; The resistivity of the material of the first conductive layer is less than that of the material of the first resistive layer.

6. The circuit board according to claim 5, characterized in that, The first conductive layer is disposed on the surface of the first resistive layer opposite to the second dielectric layer; the first conductive layer has a first opening, and the portion of the first resistive layer corresponding to the first opening serves as the thermistor.

7. The circuit board according to claim 5 or 6, characterized in that, The thickness of the first resistive layer is 10nm to 1000nm.

8. The circuit board according to any one of claims 3-7, characterized in that, At least one second conductor layer includes a second wire layer and a second resistance layer, wherein the second resistance layer includes the non-thermostat; The resistivity of the material of the second conductive layer is less than that of the material of the second resistive layer.

9. The circuit board according to claim 8, characterized in that, The second conductive layer is disposed on the surface of the second resistive layer facing the first conductive layer; the second conductive layer has a second opening, and the portion of the second resistive layer corresponding to the second opening serves as the non-thermostat.

10. The circuit board according to any one of claims 1-9, characterized in that, The plurality of resistors includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor, wherein the fourth resistor and the sixth resistor are the thermistors; One end of the first resistor is coupled to the first input terminal, and the other end of the first resistor is coupled to the first output terminal; One end of the second resistor is coupled to the first input terminal, and the other end of the second resistor is coupled to the second output terminal; One end of the third resistor is coupled to the first output terminal, and the other end of the third resistor is coupled to the second output terminal; One end of the fourth resistor is coupled to the first output terminal, and the other end of the fourth resistor is coupled to one end of the fifth resistor; The other end of the fifth resistor is coupled to one end of the sixth resistor, and the other end of the sixth resistor is coupled to the second output terminal.

11. The circuit board according to any one of claims 1-9, characterized in that, The plurality of resistors includes a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor, wherein one of the seventh resistor, the eighth resistor, the ninth resistor, and the tenth resistor is the thermistor; One end of the seventh resistor is coupled to the first input terminal, and the other end of the seventh resistor is coupled to the first output terminal; One end of the eighth resistor is coupled to the first input terminal, and the other end of the eighth resistor is coupled to the second output terminal; One end of the ninth resistor is coupled to the first output terminal, and the other end of the ninth resistor is coupled to the second input terminal; One end of the tenth resistor is coupled to the second output terminal, and the other end of the tenth resistor is coupled to the second input terminal.

12. The circuit board according to any one of claims 1-11, characterized in that, The temperature change rate of the thermistor is greater than or equal to 2Ω / ℃.

13. The circuit board according to any one of claims 1-12, characterized in that, The sheet resistance of the thermistor is 200Ω to 3000Ω, or the center resistance of the thermistor is 200Ω to 3000Ω.

14. The circuit board according to any one of claims 5-12, characterized in that, The distance between the thermistor and the first conductive part is 5μm-1mm.

15. The circuit board according to any one of claims 1-14, characterized in that, The circuit board also includes an eleventh resistor, which is coupled to the first input terminal.

16. A circuit board assembly, characterized in that, It includes a processing unit, a circuit board, and a heat source to be tested; the circuit board includes the circuit board according to any one of claims 1-15; the processing unit is coupled to a second conductive part and a third conductive part respectively; the heat source to be tested is connected to a first conductive part, or the first conductive part serves as the heat source to be tested.

17. The circuit board assembly according to claim 16, characterized in that, The circuit board assembly also includes a back-end circuit, which is coupled to the first conductive part.

18. The circuit board assembly according to claim 16, characterized in that, The circuit board assembly also includes a back-end circuit that is coupled to a Wheatstone bridge on the circuit board.

19. The circuit board assembly according to claim 16, characterized in that, The circuit board assembly also includes an excitation source, which is coupled to the first conductive part.

20. A circuit board assembly, characterized in that, This includes the processing unit, circuit board, and the heat source to be tested; The circuit board includes a first conductive portion and a second conductive portion, and a first dielectric layer, a first conductor layer and a second dielectric layer stacked sequentially; the first conductor layer includes a thermistor coupled between the first conductive portion and the second conductive portion, and the thermistor is a thin-film resistor; the processing unit is coupled to the first conductive portion or the second conductive portion. The first conductive part is connected to the heat source to be tested, or the first conductive part serves as the heat source to be tested.

21. The circuit board assembly according to claim 20, characterized in that, The circuit board further includes a first resistor and a second conductor layer, the second conductor layer being disposed on the side of the second dielectric layer away from the first conductor layer, the first resistor being located on the second conductor layer, and the first resistor and the processing unit being coupled to the same conductive portion in the first conductive portion and the second conductive portion.

22. The circuit board assembly according to claim 21, characterized in that, The circuit board assembly also includes a capacitor, which is coupled in parallel with the thermistor.

23. An electronic device, characterized in that, It includes a circuit board assembly and a mid-frame, the circuit board assembly being disposed on the mid-frame; the circuit board assembly includes the circuit board assembly according to any one of claims 16-22.

24. A method for manufacturing a circuit board, characterized in that, The circuit board includes a Wheatstone bridge; the method for manufacturing the circuit board includes: At least one second conductor layer and at least one second dielectric layer are formed; the at least one second conductor layer and the at least one second dielectric layer are alternately disposed; A first conductor layer is formed, the first conductor layer being located on the side of the second dielectric layer away from the second conductor layer; the first conductor layer includes a first conductive portion, a second conductive portion, and a third conductive portion; A first dielectric layer is formed, which covers the first conductor layer and exposes the second conductive portion and the third conductive portion. The Wheatstone bridge includes multiple resistors, a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The resistors are located in the first conductor layer or the second conductor layer. The multiple resistors include one or more thermistors. The first input terminal and the second input terminal are coupled to the first conductive part, the first output terminal is coupled to the second conductive part, and the second output terminal is coupled to the third conductive part.

25. The method for manufacturing a circuit board according to claim 24, characterized in that, Forming the first conductor layer includes: A first resistive film and a first conductive film are sequentially formed on the surface of the second dielectric layer away from the second conductor layer; The first conductive film and the first resistive film are patterned to form a first conductive film pattern and a first resistive layer; The first conductive film pattern is patterned to expose a portion of the first resistive layer, thus forming the first conductive layer.

26. The method for manufacturing a circuit board according to claim 24, characterized in that, Patterning the first conductive film and the first resistive film includes: The first conductive film and the first resistive film are patterned using exposure, development, and acid etching processes.

27. The method for manufacturing a circuit board according to claim 25 or 26, characterized in that, Patterning the first conductive film pattern includes: The first conductive film pattern is patterned using an exposure, development, and alkaline etching process.

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