Composite metal foil, metal-clad laminate, and circuit board

Abstract

The present invention discloses a composite metal foil, a metal-clad laminate, and a circuit board. The composite metal foil includes a resistor layer and a conductive layer; the conductive layer has a first surface, and the resistor layer is disposed on the first surface. In a sliced ​​state, the first surface has a trend line. Along the upper and lower sides of the trend line, within a sampling width of 10 μm, the total number of raised portions and recessed portions is less than or equal to 5. The trend line is obtained by slicing the composite metal foil along the thickness direction of the composite metal foil within a preset observation range, drawing a trend line along the first surface from left to right along the extension direction of the resistor layer, and sampling points at intervals of 80 nm to the right along the extension direction of the first surface from the starting point. If the difference in vertical height between the next sampling point and the previous sampling point is less than 50 nm, the value of the next sampling point is retained; otherwise, the value of the previous sampling point is retained. The present invention can ensure the uniformity of the resistance value of the resistor layer, thereby improving the temperature control accuracy and circuit manufacturing accuracy.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of composite metal foil, in particular to a composite metal foil, a metal-clad laminate and a circuit board. BACKGROUND

[0002] With the continuous progress of electronic industry and information technology level, electronic components develop towards high performance and miniaturization. However, heat phenomenon occurs in the running process of electronic components, and the electronic components cannot run normally with the increase of running temperature. Therefore, temperature control is needed for the electronic components to keep them running normally. To achieve this purpose, temperature control components are often arranged on the surface or side of the electronic components or chip-type thermistors are attached on the surface of the electronic components to monitor the temperature of the electronic components.

[0003] At present, the temperature control components are large in size, and the temperature monitoring by arranging temperature control components on the surface of the electronic components or attaching thermistors on the surface is not conducive to the integration of the circuit board and occupies the position of the circuit board. Since the position for use is limited, temperature monitoring components cannot be arranged on many small electronic components, and it is also difficult to monitor the heat of most electronic components, which may lead to the burning or failure of the unmonitored electronic components due to overheating, affecting the normal work of the circuit board and the terminal.

[0004] The chip-type thermistor increases or decreases in resistance with the change of temperature. However, it is large in size and high in thickness, and cannot be directly made into a thermistor in the circuit. It can only be welded on the pad after subsequent circuit processing. At present, there is no embedded resistance copper foil used as a thermistor for temperature monitoring of electronic components in the industry.

[0005] The existing thermistor products are in the form of rolls or sheets, and the size is in the form of sheets per square meter or rolls with a width of tens to hundreds of centimeters. The material is provided to the circuit board factory for the production of micron-level wide circuits. The resistance value of the material at different positions needs to be uniform to improve the use quality. At present, the resistance value uniformity of the existing thermistor material is poor, and the resistance value at different positions may differ by tens or even hundreds of milliohms, which will affect the quality of circuit production. SUMMARY

[0006] The present application provides a composite metal foil, a metal-clad laminate and a circuit board, which can ensure the uniformity of the resistance value of the resistance layer, thereby improving the temperature control precision and the circuit production precision.

[0007] According to one aspect of the present application, a composite metal foil is provided, which comprises a resistance layer and a conductive layer.

[0008] The conductive layer is provided with a first surface, and the resistance layer is arranged on the first surface, and the first surface has a trend line in a slicing state, and along the upper and lower sides of the trend line, the total number of protrusions and depressions within a sampling width of 10 μm is less than or equal to 5.

[0009] The trend line is obtained by slicing the composite metal foil in a preset observation range along the thickness direction of the composite metal foil, and the trend line is obtained from left to right along the extension direction of the resistance layer, and the sampling points are obtained by sampling at intervals of 80 nm from the starting point to the right along the extension direction of the first surface, and when the difference between the vertical heights of the next sampling point and the previous sampling point is less than 50 nm, the value of the next sampling point is retained, otherwise the value of the previous sampling point is retained, the protrusions are formed on the side of the trend line away from the conductive layer, and the depressions are formed on the side of the trend line close to the conductive layer.

[0010] Optionally, along the upper and lower sides of the trend line, the total number of protrusions and depressions within a width of 10 μm is greater than or equal to 1 and less than or equal to 5.

[0011] Optionally, along the thickness direction of the composite metal foil, the maximum depth of the depression is in the range of 50 nm to 400 nm.

[0012] Optionally, the number of depressions with a maximum depth of 50 nm to 100 nm accounts for more than 40% of all the depressions.

[0013] Optionally, along the thickness direction of the composite metal foil, the maximum height of the protrusion is in the range of 50 nm to 500 nm.

[0014] Optionally, the number of protrusions with a maximum height of 50 nm to 100 nm accounts for more than 50% of all the protrusions.

[0015] Optionally, along the direction perpendicular to the thickness direction of the composite metal foil, the maximum width of the depression is in the range of 60 nm to 300 nm.

[0016] Optionally, along the direction perpendicular to the thickness direction of the composite metal foil, the maximum width of the protrusion is in the range of 60 nm to 300 nm.

[0017] Optionally, the thickness of the resistance layer is in the range of 50 nm to 1 μm.

[0018] Optionally, the roughness Rz of the side of the conductive layer close to the resistance layer is in the range of 1 μm to 7 μm.

[0019] Optionally, the composite metal foil further comprises an adjustment layer arranged on the side of the conductive layer away from the resistance layer.

[0020] Optionally, the resistance layer has a negative temperature coefficient, and a resistance change rate of the resistance layer is greater than 5% in each 25℃ temperature change interval.

[0021] Optionally, one temperature cycle is from 25℃ to 150℃ and then to 25℃, and a resistance recovery deviation of the resistance layer is less than 10% in at least one temperature cycle.

[0022] According to another aspect of the present application, a metal-clad laminate is provided, which comprises the composite metal foil according to any of the embodiments of the present application.

[0023] According to another aspect of the present application, a circuit board is also provided, which comprises a circuit made of the composite metal foil according to any of the embodiments of the present application.

[0024] The technical scheme of the embodiments of the present application establishes the trend line of the first surface to establish the number of the recessed part and the protruding part on both sides of the trend line, controls the processing technology to make the number of the recessed part and the protruding part within the preset range be within 5, makes the first surface tend to be flat while having undulations, can improve the processing uniformity of the resistance layer under the condition of guaranteeing the bonding force with the substrate, thereby improving the temperature control precision and the circuit manufacturing precision, can realize better resistance continuity by improving the material morphology, reduces the resistance value sudden increase of the resistance layer, improves the stability and reliability of the circuit manufacturing, and guarantees the thermal management effect. In summary, the present application solves the problem that the resistance value uniformity of the existing thermistor material is poor, the resistance values at different positions can be different by tens or even hundreds of milliohms, and the circuit manufacturing quality is affected.

[0025] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Figure 1 is a structural schematic diagram of a composite metal foil according to an embodiment of the present application;

[0028] Figure 2 is a schematic diagram of a composite metal foil in a slicing state according to an embodiment of the present application;

[0029] Figure 3 is a schematic view of another composite metal foil in a sliced state according to an embodiment of the present application;

[0030] Figure 4 is a schematic view of another composite metal foil in a sliced state according to an embodiment of the present application;

[0031] Figure 5 is a schematic view of a structure of a recess according to an embodiment of the present application;

[0032] Figure 6 is a schematic view of a structure of a protrusion according to an embodiment of the present application;

[0033] Figure 7 is a schematic view of another composite metal foil according to an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0035] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0036] Figure 1 is a schematic view of a structure of a composite metal foil according to an embodiment of the present application, with reference to Figure 1 The embodiments of the present application provide a composite metal foil, which comprises: a resistance layer 10 and a conductive layer 20; the conductive layer 20 is provided with a first surface, and the resistance layer 10 is arranged on the first surface; the first surface has a trend line in a sliced state, and the total number of protrusions and recesses on both sides of the trend line within a sampling width of 10 μm is less than or equal to 5.

[0037] The trend line is obtained in the following manner: in a preset observation range, the composite metal foil is sliced along the thickness direction of the composite metal foil, the trend line is drawn on the first surface from left to right along the extension direction of the resistance layer 10, the sampling points are obtained by sampling at intervals of 80 nm from the starting point to the right along the extension direction of the first surface, when the difference between the vertical heights of the next sampling point and the previous sampling point is less than 50 nm, the value of the next sampling point is retained, otherwise, the value of the previous sampling point is retained, the protruding part is formed on the side of the trend line away from the conductive layer 20, and the recessed part is formed on the side of the trend line close to the conductive layer 20.

[0038] Optionally, the resistance layer can be formed by sputtering, electroplating, chemical plating, evaporation plating, ALD, PVD, CVD or other formation methods.

[0039] Specifically, the resistance layer 10 is formed on one side of the substrate by magnetron sputtering once or multiple times. When the resistance layer 10 is a copper layer, the copper layer is used for manufacturing a circuit board and conducting electricity, and can be used for direct etching of a temperature measuring circuit to meet the needs of circuit etching. The copper layer can be replaced by other conductive materials such as gold, silver, iron, aluminum or other metals and non-metallic materials.

[0040] The resistance layer 10 is arranged on the first surface of the conductive layer 20, and through the laminated arrangement of the conductive layer 20 and the resistance layer 10, the resistance layer 10 is pressed on the substrate. After the circuit is manufactured by a circuit manufacturing process, the resistance can be embedded in the circuit, which improves the compactness of the circuit design and is beneficial to reducing the volume of the circuit.

[0041] When the circuit board is manufactured, the side of the resistance layer away from the conductive layer is connected with the circuit board. In order to ensure the bonding force between the copper foil of the thermistor and the substrate during pressing, it is necessary to ensure that the side of the copper foil layer close to the thermistor layer is uneven, that is, the rough surface, and the resistance layer is processed on the rough surface. Figure 2 is a schematic diagram of a composite metal foil in a slicing state according to an embodiment of the present application, Figure 3 is another schematic diagram of a composite metal foil in a slicing state according to an embodiment of the present application, referring to Figure 2 and Figure 3 In the process of vacuum magnetron sputtering, due to process and material problems, the formation process of the resistance layer will grow vertically, resulting in Figure 2 holes in the left dashed circle and nanoscale hole gaps in the right dashed circle, which cannot be observed in appearance. In the slicing state, it appears as downward trenches, which will affect the continuity of the resistance layer and the uniformity of the square resistance. If such holes are just manufactured in the circuit, it will cause the resistance value to increase or even cause the circuit to be interrupted, resulting in poor quality of the circuit manufacturing. Figure 3 is a local schematic diagram of a copper tumor, Figure 3The conductive layer 20 under the middle resistance layer 10 can be a copper layer, 21 is a copper tumor on the copper layer, and 22 is a pore formed by the copper tumor 21 on the copper layer.

[0042] Figure 4 is another schematic diagram of a composite metal foil in a slicing state according to an embodiment of the present application, referring to Figure 4 , the morphology of the thermistor copper foil in the slicing state is limited, and a trend line is drawn between the resistance layer 10 and the conductive layer 20 from left to right (as shown by the black thick line in Figure 4 ), and above and below the trend line, protrusions (as indicated by the arrow above the black thick line in Figure 4 ) and depressions (as indicated by the arrow below the black thick line in Figure 4 ) will appear. By adjusting the process, a thermistor with a relatively flat copper foil layer surface is manufactured by reducing the number of protrusions and depressions, which can improve the uniformity of the resistance layer 10 while ensuring the bonding force with the substrate.

[0043] It should be noted that the establishment of the trend line refers to the filtering principle: a rectangular coordinate system is established from left to right in the slicing diagram, the demarcation point of the resistance layer and the copper foil layer is taken as the initial value of the trend line, and the sampling interval is 50nm-100nm, preferably 80nm; the amplitude limit is 30nm-80nm, preferably 50nm. If the vertical height of the next sampling point and the current sampling point is greater than 30nm, the current sampling point value is taken, and if the vertical height of the next sampling point and the current sampling point is less than 30nm, the next sampling point value is retained.

[0044] Specifically, under a sampling length of 500nm-1μm, in a sampling width of 1μm-3μm, the total number of protrusions and depressions on the opposite sides of the trend line is less than 5.

[0045] Among them, the sampling interval and amplitude limit of the trend line affect the final trend of the trend line, thereby affecting the number, width and height of the protrusions and depressions above and below the trend line. By limiting the sampling interval and sampling amplitude, the extension form of the first surface in the slicing state can be restored to the greatest extent, and the degree of protrusions and depressions obtained will have a greater impact on the growth of the resistance layer, thereby adjusting the number of protrusions and depressions to solve the problem of continuity and uniformity of the resistance layer.

[0046] The technical scheme of the embodiment of the present application establishes the number of the recessed part and the convex part on both sides of the trend line of the first surface by establishing the trend line of the first surface, controls the processing technology so that the number of the recessed part and the convex part in the preset range is within 5, makes the first surface tend to be flat while having undulations, can improve the processing uniformity of the resistance layer under the condition of guaranteeing the bonding force with the substrate, thereby improving the temperature control precision and the circuit manufacturing precision, can realize better resistance continuity by improving the material morphology, reduces the resistance value sudden increase of the resistance layer, improves the stability and reliability of circuit manufacturing, and guarantees the thermal management effect. In summary, the present application solves the problem that the resistance value uniformity of the existing thermistor material is poor, the resistance values at different positions can differ by tens or even hundreds of milliohms, and the circuit manufacturing quality is affected.

[0047] Further, along the upper and lower sides of the trend line, the total number of the convex part and the recessed part within the width of 10 μm is greater than or equal to 1 and less than or equal to 5.

[0048] Specifically, when the total number of the convex part and the recessed part is greater than or equal to 1 and less than or equal to 5, the bonding force after the composite metal foil is pressed with the substrate and the uniformity of the resistance layer can be considered. When the total number of the convex part and the recessed part in the preset observation range exceeds 5, the first surface has strong unevenness, which can cause cracks, holes, gaps and other defects in the deposition of the resistance layer, thereby affecting the quality and working performance of the thermistor. Within the range of 1-5, the production cost can be considered to obtain a composite metal foil with lower use cost and better performance.

[0049] Figure 5 is a structure diagram of a recessed part according to the embodiment of the present application. In an embodiment, as shown in Figure 5 , along the thickness direction of the composite metal foil, the maximum depth D of the recessed part ranges from 50 nm to 400 nm. The depth of the recessed part in the above range can reduce the influence on the continuity of the resistance layer deposition, while guaranteeing the yield and reducing the use cost.

[0050] Further, as shown in Figure 5 , the number of the recessed part with the maximum depth of 50 nm to 100 nm accounts for more than 40% of the total number of all recessed parts. The number of the recessed part is an integer. Therefore, by adjusting the size ratio of the recessed part, the proportion of the depth range in the above interval is large, and the proportion of the recessed part with a large depth range is small, which is conducive to guaranteeing the continuity of the resistance layer processing while reducing the production cost, and further guaranteeing the square resistance uniformity. At the same time, it can avoid the phenomenon of excessive etching of the conductive layer during etching of the circuit, so as to cause unstable bonding force and circuit falling off.

[0051] In an embodiment, Figure 6 is a structure diagram of a convex part according to the embodiment of the present application. Referring toFigure 6 The maximum height H of the protrusion part ranges from 50 nm to 500 nm along the thickness direction of the composite metal foil. Within this range, on the one hand, the production cost can be reduced, the yield can be improved under the condition of use, and the use cost can be reduced, and at the same time, the bonding force of the composite metal foil and the substrate after pressing can be ensured, and the problem of uneven resistance layer caused by too large protrusion height can be avoided, and the uniformity of sheet resistance can be improved.

[0052] Further, as shown in Figure 6 , the protrusion parts with a maximum height H of 50 nm to 100 nm account for more than 50% of the total number of protrusion parts. The number of protrusion parts is an integer. The small-size protrusion parts have a larger number ratio, which further controls the use cost and ensures the uniformity of resistance processing.

[0053] In one embodiment, as shown in Figure 5 , the maximum width W1 of the recess part ranges from 60 nm to 300 nm along the direction perpendicular to the thickness direction of the composite metal foil. The maximum width W1 of the recess part is within the above range, so that the recess width distance is small in the sliced state, the overall area of the recess part is controlled within the range that meets the use, which is beneficial to further reduce the influence on the continuity of resistance layer deposition, while ensuring the yield and reducing the use cost.

[0054] In one embodiment, as shown in Figure 6 , the maximum width W2 of the protrusion part ranges from 60 nm to 300 nm along the direction perpendicular to the thickness direction of the composite metal foil. The maximum width W2 of the protrusion part is within the above range, so that the protrusion width distance is large in the sliced state, the overall area of the protrusion part is controlled within the range that meets the use, which can further increase the cross section of the resistance layer, thereby improving the ESD performance of the resistance layer, effectively ensuring that the embedded resistance has strong anti-static breakdown capability, while ensuring the yield and reducing the use cost.

[0055] Continuing to refer to Figure 1 , further, the thickness of the resistance layer 10 ranges from 50 nm to 1 μm.

[0056] Specifically, the resistance layer 10 is formed on one side of the copper foil by magnetron sputtering one or more times (or other physical, chemical plating process) with a thickness of 50 nm to 1 μm. Within this range, the thickness is adjusted to increase the resistance value, so as to increase the temperature coefficient, and when the film thickness is very thin, the carriers can jump between different conductive regions through quantum tunneling effect, resulting in a very sensitive conductivity to temperature, thereby increasing the temperature coefficient of resistance (TCR). The thinner the film, the greater the residual stress, especially in physical vapor deposition processes such as sputtering. Residual stress can cause microstructure defects such as increased grain boundary and vacancy density, thereby increasing the temperature sensitivity of the resistance and increasing the TCR. The thinner the film, the shorter the heat diffusion path, and the faster the local temperature change in the material, which will make the temperature response of the thin film faster and the TCR increase. When the film thickness is very thin, the carriers can jump between different conductive regions through quantum tunneling effect, resulting in a very sensitive conductivity to temperature, thereby increasing the TCR.

[0057] With reference to the foregoing Figure 1 Further, the roughness Rz of the side of the conductive layer 20 close to the resistance layer 10 is in the range of 1 μm to 7 μm.

[0058] By laminating the conductive layer 20 and the resistance layer 10, pressing them on the substrate, and making the circuit through the circuit making process, the resistance can be embedded in the circuit, the compactness of the circuit design is improved, and the volume of the circuit is reduced.

[0059] It should be noted that the resistance value test condition of the resistance layer is to measure on the resistance layer material with a length-width ratio of 1:1.

[0060] Optionally, the conductive layer material includes a single metal layer and / or an alloy layer; the single metal layer is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy layer is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.

[0061] Specifically, the conductive layer is a copper foil. With reference to the foregoing Figure 1 Further, the thickness of the conductive layer 20 is 5 μm to 100 μm. The roughness Rz of the side of the conductive layer 20 close to the resistance layer 10 is in the range of 1 μm to 7 μm. When the resistance layer 10 is a copper layer, it can be used for direct etching of the temperature measuring circuit, meet the needs of circuit etching, and improve the stability of current transmission, while controlling the use cost. The roughness in the above range can further ensure the bonding force between the resistance layer 10 and the conductive layer 20, and the bonding force after the composite metal foil is pressed on the substrate, so as to avoid the circuit from falling off.

[0062] Figure 7is a structural schematic diagram of yet another composite metal foil according to an embodiment of the present application, referring to Figure 7 In one embodiment, the composite metal foil further comprises an adjusting layer 30, which is arranged on the side of the conductive layer 20 away from the resistance layer 10.

[0063] Optionally, the adjusting layer 30 can be made of a coupling agent, an adhesive, or other materials.

[0064] Specifically, the adjusting layer 30 is usually a silane coupling agent, and the adjusting layer 30 serves to improve the bonding force between the thermistor copper foil and the substrate after being pressed on the substrate, so as to avoid falling off.

[0065] Optionally, the resistance layer is made of Ni (nickel), Cr (chromium), Zn (zinc), Al (aluminum), Sn (tin), O (oxygen), N (nitrogen), Cu (copper), Mn (manganese), or other elements that can achieve good thermosensitive properties.

[0066] Specifically, the first resistance layer is made of a nickel-iron oxide alloy. Nickel-iron oxide belongs to ferrite materials, has good temperature sensitivity, and its resistance changes with temperature in a stable nonlinear relationship, which can be used for accurate temperature measurement and can work in a wide temperature range, has chemical and thermal stability, can maintain stable performance in long-term use or harsh environments (such as high temperature or high humidity), has relatively low manufacturing cost, and is suitable for mass production. By changing the ratio of nickel and iron or doping other elements (such as manganese and zinc), the resistance temperature characteristic can be adjusted to meet the specific application requirements.

[0067] Further, in the resistance layer, the composition ratio is preferably: Fe (iron) content less than 30%, Ni content greater than 30%, and O content less than 60%. Such a composition ratio can on the one hand more easily achieve etching, and on the other hand further improve temperature sensitivity and thermal stability, and improve the use quality of the composite metal foil.

[0068] When the composite metal foil is arranged in a circuit board for temperature monitoring, the voltage and current changes of the circuit in the circuit board are monitored through the thermosensitive effect of the first resistance layer 10, so as to realize the heat monitoring and even feedback regulation of electronic components.

[0069] In one embodiment, the resistance layer has a negative temperature coefficient, and the resistance change rate of the resistance layer is greater than 5% in each 25℃ temperature change interval.

[0070] Specifically, the resistance layer of the composite metal foil has the property of a thermistor, which is reflected in that the resistance of the resistance layer changes with the increase of temperature and / or the resistance of the resistance layer changes with the decrease of temperature. The working temperature of the to-be-tested component can be monitored in real time through the change of the resistance value of the thin-film resistance, and the to-be-tested component can be protected in time through other temperature control circuits when the preset temperature is exceeded, so as to avoid the burning of the electronic component due to the excessively high temperature.

[0071] For example, the resistance value of the resistance layer changes by 6%, 7%, 8%, 10%, 12%, 14%, 16%, 20% or other values per 25℃ temperature change. In this way, the resistance value of the thermistor changes more greatly in a specific temperature range, thereby improving the response speed of the thermal management circuit to the slight temperature change, the accuracy can meet the use of the thermistor in the terminal, and the detection sensitivity is improved.

[0072] In one embodiment, the temperature rises from 25℃ to 150℃ and then drops to 25℃ for one temperature cycle, and the resistance value recovery deviation of the resistance layer is less than 10% in at least one temperature cycle.

[0073] Specifically, the resistance value recovery deviation of the resistance layer is less than 10% in at least one temperature cycle, which ensures that the resistance value of the composite metal foil in the temperature measurement circuit is stable, so that the voltage change in the temperature measurement circuit is stable, the voltage does not change greatly, the normal work of the temperature measurement circuit is ensured, and the use of other active devices is not affected by the large voltage difference in the temperature measurement process of the composite metal foil.

[0074] Embodiment 1

[0075] A composite metal foil includes a resistance layer and a conductive layer, the material of the conductive layer is Cu, the thickness of the conductive layer is 18μm, the material of the resistance layer is nickel-iron oxide, and the thickness of the resistance layer is 360nm. After obtaining a slice image, a trend line is established on the first surface, the number of convex parts and concave parts is counted, and the number of convex parts is 0 and the number of concave parts is 12 within a sampling width of 5μm.

[0076] Embodiment 2

[0077] Different from embodiment 1, the resistance layer includes ferrite, and the thickness of the resistance layer is 440nm. After obtaining a slice image, a trend line is established on the first surface, and the number of convex parts is 2 and the number of concave parts is 3 within a sampling width of 2μm. Among all the convex parts, the average maximum width is 45nm and the average maximum height is 76nm. Among all the concave parts, the average maximum width is 65nm and the average maximum depth is 200nm.

[0078] Embodiment 3

[0079] Different from example 1, the composite metal foil further comprises an adjustment layer, the adjustment layer is arranged on the back of the resistance layer away from the conductive layer, the material of the adjustment layer is silane coupling agent, the elements of the resistance layer include nickel, iron, aluminum and oxygen, and the thickness of the resistance layer is 660 nm. After obtaining the slice image, a trend line is established on the first surface, and within a sampling width of 2 μm, the number of protruding parts is 2 and the number of recessed parts is 3. Among them, the average maximum width of all protruding parts is 45 nm, and the average maximum height is 76 nm. Among all the recessed parts, the average maximum width is 65 nm, and the average maximum depth is 200 nm.

[0080] Comparative example 1

[0081] The composite metal foil comprises a resistance layer and a conductive layer, wherein the material of the conductive layer is Cu, the thickness of the conductive layer is 18 μm, the material of the resistance layer is nickel-phosphorus alloy, and the thickness of the resistance layer is 2.5 μm. After obtaining the slice image, a trend line is established, and within a sampling width of 2 μm, the number of protruding parts is 1 and the number of recessed parts is 7.

[0082] Comparative example 2

[0083] Different from comparative example 1, the material of the resistance layer is nickel-iron oxide, and the thickness of the resistance layer is 780 μm. After obtaining the slice image, a trend line is established, and within a sampling width of 2 μm, the number of protruding parts is 4 and the number of recessed parts is 11. Among them, the average maximum width of all protruding parts is 155 nm, and the average maximum height is 342 nm. Among all the recessed parts, the average maximum width is 125 nm, and the maximum depth is 450 nm.

[0084] The composite metal foil of the above examples and comparative examples is used to make samples, which are pressed on the Core of the P-coated sheet at 185℃ for 10 min, and then the copper layer is removed by using an alkaline etching solution, and after cleaning, the samples are placed in an oven at 105℃ for 10 min to remove moisture; a small grid of 2 cm x 2 cm is marked on the surface of the sample after the copper is removed by alkaline etching, and the square resistance of each grid is tested by using a square resistance meter, and the square resistance uniformity is counted and measured, and the test results are shown in Table 1 as follows:

[0085] Table 1

[0086]

[0087]

[0088] As can be seen from the above table data, the composite metal foil of examples 1-3 can have higher square resistance uniformity, which is beneficial to improve the use quality.

[0089] The examples of the present application provide a metal-clad laminate, which comprises the composite metal foil of any example of the present application.

[0090] Since the metal-clad laminate includes the composite metal foil provided by any of the embodiments of the present application, the metal-clad laminate has the same advantages as the composite metal foil, which will not be repeated here.

[0091] The embodiments of the present application also provide a circuit board, which includes the circuit made of the composite metal foil of any of the embodiments of the present application.

[0092] Specifically, the composite metal foil can be a thermistor copper foil. The thermistor copper foil is embedded in the circuit with a micron-level line width to make the circuit board, which does not occupy the component placement position of the circuit board, and is matched with a temperature monitoring circuit. The change of voltage and current in the circuit caused by temperature change can realize the heat monitoring and even feedback regulation of electronic components.

[0093] The composite metal foil can be arranged on the circuit and the component surface of the circuit board to measure the temperature of the circuit or the component. The circuit board of the embodiments of the present application includes the composite metal foil, which can monitor the temperature of the circuit board to avoid damage of the circuit board caused by high temperature.

[0094] Since the circuit board includes the composite metal foil provided by any of the embodiments of the present application, the circuit board has the same advantages as the composite metal foil, which will not be repeated here.

[0095] The above specific embodiments do not constitute a limitation on the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A composite metal foil, characterized in that include: Resistive layer and conductive layer; The conductive layer has a first surface, the resistive layer is disposed on the first surface, the first surface has a trend line in a sliced ​​state, and along upper and lower sides of the trend line, within a sampling width of 10 μm, the total number of raised portions and recessed portions is less than or equal to 5; The trend line is obtained as follows: within a preset observation range, the composite metal foil is sliced ​​along the thickness direction of the composite metal foil, a trend line is drawn on the first surface from left to right along the extension direction of the resistance layer, and sampling points are obtained from the starting point along the extension direction of the first surface at intervals of 80 nm to the right. When the difference in vertical height between the next sampling point and the previous sampling point is less than 50 nm, the value of the next sampling point is retained; otherwise, the value of the previous sampling point is retained. The raised portion is formed on the side of the trend line away from the conductive layer, and the depressed portion is formed on the side of the trend line close to the conductive layer.

2. The composite metal foil according to claim 1, characterized in that Along the upper and lower sides of the trend line, within a width of 10 μm, the total number of the protruding portions and the recessed portions is greater than or equal to 1 and less than or equal to 5.

3. The composite metal foil according to claim 1, characterized in that Along the thickness direction of the composite metal foil, the maximum depth of the recessed portion ranges from 50 nm to 400 nm.

4. The composite metal foil according to claim 3, characterized in that The number of the depressed portions with a maximum depth of 50 nm to 100 nm accounts for more than 40% of all the depressed portions.

5. The composite metal foil according to claim 1, characterized in that Along the thickness direction of the composite metal foil, the maximum height of the protrusion is in the range of 50 nm to 500 nm.

6. The composite metal foil according to claim 5, characterized in that The number of protrusions with a maximum height of 50 nm to 100 nm accounts for more than 50% of all the protrusions.

7. The composite metal foil according to claim 1, characterized in that Along a direction perpendicular to the thickness of the composite metal foil, the maximum width of the recessed portion ranges from 60 nm to 300 nm.

8. The composite metal foil according to claim 1, characterized in that Along a direction perpendicular to the thickness of the composite metal foil, the maximum width of the protrusion is in a range of 60 nm to 300 nm.

9. The composite metal foil according to claim 1, characterized in that The thickness of the resistance layer ranges from 50 nm to 1 μm.

10. The composite metal foil according to claim 1, characterized in that The roughness Rz of the side surface of the conductive layer close to the resistance layer is in a range of 1 μm to 7 μm.

11. The composite metal foil according to claim 1, characterized in that It also includes an adjustment layer, which is arranged on a side of the conductive layer away from the resistance layer.

12. The composite metal foil according to claim 1, characterized in that The resistance layer has a negative temperature coefficient, and within a temperature change interval of 25° C., the resistance value change rate of the resistance layer is greater than 5%.

13. The composite metal foil according to claim 12, characterized in that The temperature rises from 25° C. to 150° C. and then drops back to 25° C. as one temperature cycle. In at least one temperature cycle, the resistance value recovery deviation of the resistor layer is less than 10%.

14. A metal-clad laminate, characterized in that: The composite metal foil according to any one of claims 1 to 13 is provided on the surface of the metal-clad laminate.

15. A circuit board, characterized in that: The circuit board comprises the composite metal foil according to any one of claims 1 to 13.

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