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

Abstract

The invention discloses a composite metal foil, a metal-clad laminated board and a circuit board. The composite metal foil comprises a resistive layer and a conductive layer; the conductive layer is provided with a first surface, the resistance layer is arranged on the first surface, the first surface is provided with a trend line in a slicing state, and the total number of the convex parts and the concave parts is smaller than or equal to 5 along the upper side and the lower side of the trend line within the sampling width of 10 microns; the obtaining method of the trend line comprises the following steps: in a preset observation range, slicing the composite metal foil along the thickness direction of the composite metal foil, making the trend line on the first surface from left to right along the extension direction of the resistive layer, sampling from the starting point to the right along the extension direction of the first surface at an interval of 80nm to obtain sampling points, when the difference between the vertical height of the next sampling point and the vertical height of the previous sampling point is smaller than 50nm, the value of the next sampling point is reserved, otherwise, the value of the previous sampling point is reserved. The uniformity of the resistance value of the resistive layer can be ensured, so that the temperature control precision and the circuit manufacturing precision are improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of composite metal foils, and in particular to a composite metal foil, a metal-clad laminate and a circuit board. Background Art

[0002] With the continuous advancement of the electronics industry and information technology, electronic components are developing towards high performance and miniaturization. However, electronic components will generate heat during operation. As the operating temperature increases, the electronic components will not be able to operate normally. Therefore, it is necessary to control the temperature of the electronic components to keep them operating normally. To achieve this goal, temperature control elements are often set on the surface or side of the electronic components, or chip thermistors are attached to the surface of the electronic components to monitor the temperature of the electronic components.

[0003] At present, the volume of temperature control elements is relatively large. Setting temperature control elements or surface-mounted thermistors on the surface of electronic components to achieve temperature monitoring is not conducive to the integration of circuit boards and occupies space on the circuit boards. Due to the limited location of its use, it is not possible to set temperature monitoring elements on many small electronic components, and it is also difficult to monitor the heat generation of most electronic components. Inadequate heat monitoring may result in the unmonitored electronic components being burned or failing due to overheating, affecting the normal operation of the circuit board and the terminal.

[0004] The resistance of chip thermistors increases or decreases with temperature changes. However, they are large in size and thick in thickness, so they cannot be directly made into the circuit to form thermistors. They can only be soldered to the pads after subsequent circuit processing. At present, the industry does not use embedded resistor copper foil as thermistors for temperature monitoring of electronic components.

[0005] Existing thermistor products are in the form of rolls or sheets, with sizes ranging from square meters to sheets or tens to hundreds of centimeters wide. The materials are provided to circuit board manufacturers for making micron-level wide circuits. The resistance values ​​of different positions of the material must be uniform to improve the quality of use. At present, the resistance uniformity of existing thermistor materials is poor, and the resistance values ​​at different positions may differ by tens or even hundreds of milliohms, which will affect the quality of circuit production. Summary of the invention

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

[0007] According to one aspect of the present invention, there is provided a composite metal foil, the composite metal foil comprising: a resistance layer and a conductive layer;

[0008] The conductive layer is provided with a first surface, the resistance layer is provided on the first surface, the first surface has a trend line in a sliced ​​state, and 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;

[0009] The trend line is obtained in the following manner: 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 resistor 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 next sampling point value is retained, otherwise the previous sampling point value is retained. The raised portion is formed on a side of the trend line away from the conductive layer, and the depressed portion is formed on a side of the trend line close to the conductive layer.

[0010] Optionally, 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 depressed portions 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 recessed portion ranges from 50 nm to 400 nm.

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

[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 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.

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

[0017] Optionally, the resistance layer has a thickness ranging from 50 nm to 1 μm.

[0018] Optionally, the roughness Rz of the side surface of the conductive layer close to the resistance layer ranges from 1 μm to 7 μm.

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

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

[0021] Optionally, the temperature rises from 25° C. to 150° C. and then drops to 25° C. as one temperature cycle, and within at least one temperature cycle, the resistance value recovery deviation of the resistor layer is less than 10%.

[0022] According to another aspect of the present invention, there is provided a metal-clad laminate, wherein the metal-clad laminate comprises the composite metal foil according to any embodiment of the present invention.

[0023] According to another aspect of the present invention, there is further provided a circuit board, wherein the circuit board comprises a circuit made of the composite metal foil described in any embodiment of the present invention.

[0024] The technical solution of the embodiment of the present invention establishes the number of recessed parts and raised parts on both sides of the trend line by establishing the trend line of the first surface, and controls the processing technology so that the number of recessed parts and raised parts within the preset range is within 5, so that the first surface tends to be flat and has ups and downs. Under the condition of ensuring the bonding force with the substrate, the processing uniformity of the resistor layer can be improved, thereby improving the temperature control accuracy and circuit manufacturing accuracy; by improving the material morphology, better resistance continuity can be achieved, the sudden increase of the resistance value of the resistor layer can be reduced, the stability and reliability of circuit manufacturing can be improved, and the thermal management effect can be guaranteed. In summary, the present invention solves the problem that the existing thermistor material has poor resistance uniformity, and the resistance values ​​at different positions may differ by tens or even hundreds of milliohms, which will affect the quality of circuit manufacturing.

[0025] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

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

[0028] Figure 2 is a schematic diagram of a composite metal foil in a sliced ​​state provided by an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of another composite metal foil in a sliced ​​state provided by an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of another composite metal foil in a sliced ​​state provided by an embodiment of the present invention;

[0031] Figure 5 is a schematic structural diagram of a recessed portion provided according to an embodiment of the present invention;

[0032] Figure 6 is a schematic structural diagram of a protrusion provided according to an embodiment of the present invention;

[0033] Figure 7 It is a schematic diagram of the structure of another composite metal foil provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0036] Figure 1 is a schematic diagram of the structure of a composite metal foil provided according to an embodiment of the present invention, Figure 1 An embodiment of the present invention provides a composite metal foil, comprising: a resistance layer 10 and a conductive layer 20; the conductive layer 20 is provided with a first surface, the resistance layer 10 is arranged on the first surface, the first surface has a trend line in a sliced ​​state, 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.

[0037] The trend line is obtained in the following manner: 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 resistor layer 10, 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 next sampling point value is retained, otherwise the previous sampling point value is retained. The raised portion is formed on the side of the trend line away from the conductive layer 20, and the depressed portion is formed on the side of the trend line close to the conductive layer 20.

[0038] Optionally, the resistance layer may be formed by spraying, electroplating, chemical plating, evaporation plating, ALD, PVD, CVD or other forming 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 to make a circuit board and conduct electricity, and can be used to directly etch a temperature measurement 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 or non-metallic materials.

[0040] The resistor layer 10 is arranged on the first surface of the conductive layer 20. By stacking the conductive layer 20 and the resistor layer 10, pressing them onto the substrate, and making a circuit through a circuit manufacturing process, the resistor can be buried in the circuit, thereby improving the compactness of the circuit design and helping to reduce the circuit volume.

[0041] When making the circuit board, the side of the resistor layer away from the conductive layer is connected to the circuit board. In order to ensure the bonding force between the thermistor copper foil and the substrate during lamination, it is necessary to ensure that the side of the copper foil layer close to the thermistor layer is rough and uneven, referred to as the rough surface, and the resistor layer is processed on the rough surface. Figure 2 is a schematic diagram of a composite metal foil in a sliced ​​state provided by an embodiment of the present invention, Figure 3 is a schematic diagram of another composite metal foil sliced ​​according to an embodiment of the present invention, referring to Figure 2 and Figure 3 During the vacuum magnetron sputtering process, due to process and material problems, the formation process of the resistance layer will grow vertically, resulting in Figure 2 The hole in the dotted circle on the left and the nanometer-level hole gap in the dotted circle on the right cannot be observed from the outside. In the sliced ​​state, it appears as a downward-pointing gully, which will affect the continuity of the resistor layer and the uniformity of the square resistance. If such a hole is made in the circuit, it will increase the resistance value or even interrupt the circuit, resulting in poor circuit manufacturing quality. Figure 3 This is a partial schematic diagram of the copper tumor. Figure 3The conductive layer 20 below the medium resistance layer 10 may be a copper layer, 21 is a copper nodule on the copper layer, and 22 is a pore formed by the copper nodule 21 on the copper layer.

[0042] Figure 4 is a schematic diagram of another composite metal foil sliced ​​according to an embodiment of the present invention, referring to Figure 4 , define the morphology of the thermistor copper foil slice state, and draw a trend line between the resistance layer 10 and the conductive layer 20 from left to right (such as Figure 4 ), there will be bumps above and below the trend line (as shown in the thick black line in Figure 4 The black thick line above the arrow) and the depression (such as Figure 4 By adjusting the process to reduce the number of depressions and protrusions, a thermistor with a relatively flat copper foil surface is manufactured, and the processing uniformity of the resistor layer 10 can be improved while ensuring the bonding strength 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 slice diagram, and the boundary point between the resistor layer and the copper foil layer is found as the initial value of the trend line starting point, and the sampling interval to the right is 50nm to 100nm, preferably 80nm; the upper and lower limits are 30nm to 80nm, preferably 50nm. If the vertical height between the next sampling point and the current sampling point is greater than 30nm, the value of the current sampling point is taken; if the vertical height between the next sampling point and the current sampling point is less than 30nm, the value of the next sampling point is retained.

[0044] Specifically, at a sampling length of 500 nm to 1 μm and a sampling width of 1 μm to 3 μm, the total number of raised portions and depressed portions on 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 direction of the trend line, thereby affecting the number, width and height of the convexities and concavities above and below the trend line. By limiting the sampling interval and sampling limit, the extended form of the first surface in the sliced ​​state can be restored to the greatest extent, and the degree of the obtained convexities and concavities will have a greater impact on the growth and formation of the resistor layer, thereby solving the problem of continuity and uniformity of the resistor layer by adjusting the number of convexities and concavities.

[0046] The technical solution of the embodiment of the present invention establishes the number of recessed parts and raised parts on both sides of the trend line by establishing the trend line of the first surface, and controls the processing technology so that the number of recessed parts and raised parts within the preset range is within 5, so that the first surface tends to be flat and has ups and downs. Under the condition of ensuring the bonding force with the substrate, the processing uniformity of the resistor layer can be improved, thereby improving the temperature control accuracy and circuit manufacturing accuracy; by improving the material morphology, better resistance continuity can be achieved, the sudden increase of the resistance value of the resistor layer can be reduced, the stability and reliability of circuit manufacturing can be improved, and the thermal management effect can be guaranteed. In summary, the present invention solves the problem that the existing thermistor material has poor resistance uniformity, and the resistance values ​​at different positions may differ by tens or even hundreds of milliohms, which will affect the quality of circuit manufacturing.

[0047] Furthermore, 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 depressed portions is greater than or equal to 1 and less than or equal to 5.

[0048] Specifically, when the total number of raised portions and recessed portions is greater than or equal to 1 and less than or equal to 5, the bonding force between the composite metal foil and the substrate after lamination and the uniformity of the resistor layer can be taken into account. When the total number of raised portions and recessed portions within the preset observation range exceeds 5, the unevenness of the first surface is strong, which will cause defects such as cracks, holes, and gaps in the deposition of the resistor layer, thereby affecting the quality and working performance of the thermistor. Within the range of 1 to 5, the production cost can be comprehensively considered to obtain a composite metal foil with lower use cost and better performance.

[0049] Figure 5 is a schematic diagram of a structure of a recessed portion provided according to an embodiment of the present invention. In one embodiment, Figure 5 As shown, along the thickness direction of the composite metal foil, the maximum depth D of the concave portion ranges from 50nm to 400nm. The depth of the concave portion within the above range can reduce the impact on the continuity of the resistor layer deposition, while ensuring the yield and reducing the use cost.

[0050] Furthermore, if Figure 5 As shown, the number of depressions with a maximum depth of 50nm to 100nm accounts for more than 40% of all depressions. The number of depressions is an integer. Therefore, by adjusting the size ratio of the depressions, the depth range in the above interval accounts for a larger proportion, and the depressions with a larger depth range account for a smaller proportion, which is conducive to ensuring the continuity of the resistance layer processing while reducing the production cost, thereby ensuring the uniformity of the square resistance. At the same time, it avoids the transition etching of the conductive layer during etching of the circuit, resulting in unstable bonding force and circuit shedding.

[0051] In one embodiment, Figure 6 is a schematic diagram of a structure of a protrusion provided according to an embodiment of the present invention, with reference to Figure 6 , along the thickness direction of the composite metal foil, the maximum height H of the protrusion is in the range of 50nm to 500nm. Within this range, on the one hand, the production cost can be reduced, the yield rate can be improved while ensuring use, thereby reducing the use cost, and at the same time, the bonding force between the composite metal foil and the substrate after pressing can be ensured, while avoiding the problem of uneven resistance layer caused by excessive protrusion height, and improving the uniformity of square resistance.

[0052] Furthermore, if Figure 6 As shown, the number of protrusions with a maximum height H of 50nm to 100nm accounts for more than 50% of all protrusions. The number of protrusions is an integer. Small-sized protrusions have a larger number ratio, which further controls the use cost and ensures the uniformity of resistor processing.

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

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

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

[0056] Specifically, the resistor layer 10 is formed on one side of the copper foil by magnetron sputtering once or multiple times (or formed by other physical or chemical plating processes), and the thickness is 50nm to 1μm. Within this range, the thickness is adjusted to increase the resistance value, so that the temperature coefficient is increased and the detection accuracy is improved. When the film thickness is very thin, the carriers may jump between different conductive areas through the quantum tunneling effect, causing the conductivity to be very sensitive to temperature, thereby increasing the temperature coefficient of resistance (TCR). The thinner the film, the greater the residual stress is usually, especially in physical vapor deposition processes such as sputtering. Residual stress can cause microstructural defects, such as an increase in grain boundaries and vacancy density, thereby increasing the temperature sensitivity of the resistor and improving the TCR. The thinner the film, the shorter the heat diffusion path and the faster the local temperature changes in the material, which will accelerate the temperature response of the film and increase the TCR. When the film thickness is very thin, the carriers may jump between different conductive areas through the quantum tunneling effect, causing the conductivity to be very sensitive to temperature, thereby improving the TCR.

[0057] Continue to refer Figure 1 Furthermore, the roughness Rz of the side surface of the conductive layer 20 close to the resistance layer 10 is in the range of 1 μm to 7 μm.

[0058] By stacking the conductive layer 20 and the resistor layer 10, pressing them onto the substrate, and manufacturing the circuit through a circuit manufacturing process, the resistor can be buried in the circuit, thereby improving the compactness of the circuit design and helping to reduce the volume of the circuit.

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

[0060] Optionally, the conductive layer material includes a single metal layer and / or an alloy layer; wherein 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 copper foil. Figure 1 , further, the thickness of the conductive layer 20 is 5μm to 100μm. The roughness Rz of the side of the conductive layer 20 close to the resistor layer 10 is in the range of 1μm to 7μm. When the resistor layer 10 is a copper layer, it can be used to directly etch a temperature measurement circuit to meet the needs of circuit etching, and improve the stability of current transmission while controlling the cost of use. The roughness within the above range can further ensure the bonding force between the resistor layer 10 and the conductive layer 20, and at the same time ensure the bonding force between the composite metal foil and the substrate after pressing, to prevent the circuit from falling off.

[0062] Figure 7is a schematic diagram of the structure of another composite metal foil provided according to an embodiment of the present invention, Figure 7 In one embodiment, the composite metal foil further includes an adjustment layer 30 , and the adjustment layer 30 is disposed on a side of the resistance layer 10 away from the conductive layer 20 .

[0063] Optionally, the material of the adjustment layer 30 may be a coupling agent, an adhesive or other materials.

[0064] Specifically, the adjustment layer 30 is usually a silane coupling agent. The function of the adjustment layer 30 is to enhance the bonding force between the thermistor copper foil pressed on the substrate and the substrate to prevent it from falling off.

[0065] Optionally, the material of the resistance layer includes 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 thermal sensitivity.

[0066] Specifically, the material of the first resistance layer is nickel-iron oxide alloy. Nickel-iron oxide belongs to ferrite material, has good temperature sensitivity, and its resistance shows a stable nonlinear relationship with temperature change. It can be used to accurately measure temperature changes, and can work in a wide temperature range. It 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 large-scale production. By changing the ratio of nickel to iron or doping other elements (such as manganese and zinc), its resistance-temperature characteristics can be adjusted to meet specific application requirements.

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

[0068] When the composite metal foil is arranged in a circuit board for temperature monitoring, the changes of voltage and current in the circuit of the circuit board are monitored through the thermal effect of the first resistor layer 10, thereby realizing the heating monitoring and even feedback regulation of electronic components.

[0069] In one embodiment, the resistor layer has a negative temperature coefficient, and within a temperature change interval of 25° C., the resistance value change rate of the resistor layer is greater than 5%.

[0070] Specifically, the resistance layer of the composite metal foil has the properties of a thermistor, which means that the resistance of the resistor changes as the temperature rises, and / or the resistance of the resistance layer changes as the temperature drops. The operating temperature of the component to be tested can be monitored in real time through the change in the resistance value of the thin film resistor. When the preset temperature is exceeded, other temperature control circuits can be used to provide timely protection, thereby protecting the component to be tested and preventing the electronic components from being burned out due to excessive temperature.

[0071] For example, for every 25°C temperature change, the resistance value of the resistor layer changes by 6%, 7%, 8%, 10%, 12%, 14%, 16%, 20% or other values. This makes the resistance value of the thermistor change more within a specific temperature range, thereby improving the response speed of the thermal management circuit to small temperature changes, and the accuracy can meet the use of the thermistor in the terminal, thereby improving the detection sensitivity.

[0072] In one embodiment, the temperature rises from 25° C. to 150° C. and then drops 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%.

[0073] Specifically, within at least one temperature cycle, the resistance recovery deviation of the resistor layer is less than 10%, ensuring that the resistance of the composite metal foil in the temperature measurement circuit is stable, thereby ensuring that the voltage change in the temperature measurement circuit is stable, avoiding large jumps in voltage, ensuring the normal operation of the temperature measurement circuit, and avoiding large voltage differences during the temperature measurement of the composite metal foil that affect the use of other active devices.

[0074] Example 1

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

[0076] Example 2

[0077] Different from Example 1, the element of the resistor layer includes ferrite, and the thickness of the resistor layer is 440nm. After acquiring the slice image, a trend line is established on the first surface. Within the sampling width of 2μm, the number of protrusions is 2 and the number of depressions is 3. Among all the protrusions, the average maximum width is 45nm and the average maximum height is 76nm. Among all the depressions, the average maximum width is 65nm and the average maximum depth is 200nm.

[0078] Example 3

[0079] Different from Example 1, the composite metal foil also includes an adjustment layer, which is arranged on the side of the resistor layer facing away from the conductive layer. The material of the adjustment layer is a silane coupling agent. The elements of the resistor layer include nickel, iron, aluminum, and oxygen, and the thickness of the resistor layer is 660nm. After acquiring the slice image, a trend line is established on the first surface. Within the sampling width of 2μm, the number of protrusions is 2 and the number of depressions is 3. Among them, the average maximum width of all protrusions is 45nm, and the average maximum height is 76nm. Among all the depressions, the average maximum width is 65nm and the average maximum depth is 200nm.

[0080] Comparative Example 1

[0081] The composite metal foil includes a resistor layer and a conductive layer, wherein the conductive layer is made of Cu and has a thickness of 18 μm, and the resistor layer is made of a nickel-phosphorus alloy and has a thickness of 2.5 μm. After acquiring the slice image, a trend line is established. Within a sampling width of 2 μm, there is one convex portion and seven concave portions.

[0082] Comparative Example 2

[0083] Different from Comparative Example 1, the material of the resistor layer is nickel iron oxide, and the thickness of the resistor layer is 780 μm. After acquiring the slice image, a trend line is established. Within the sampling width of 2 μm, the number of protrusions is 4 and the number of depressions is 11. Among them, the average maximum width of all protrusions is 155 nm and the average maximum height is 342 nm. Among all depressions, the average maximum width is 125 nm and the maximum depth is 450 nm.

[0084] The composite metal foils of the above-mentioned embodiments and comparative examples were used to make samples, and were pressed onto the core of the P-covered sheet at 185°C for 10 minutes. The copper layer was removed with an alkaline etching solution, and after cleaning, the samples were placed in an oven at 105°C for 10 minutes to remove moisture. Small grids of 2 cm×2 cm were marked on the surface of the sample after alkaline etching to remove copper, and the square resistance of each grid was tested with a square resistance meter. The square resistance uniformity was statistically measured, and the test results are shown in Table 1 below:

[0085] Table 1

[0086]

[0087]

[0088] By comparing the data in the above table, it can be seen that the composite metal foils of Examples 1 to 3 can have higher uniformity of square resistance, which is beneficial to improving the quality of use.

[0089] An embodiment of the present invention provides a metal-clad laminate, which includes the composite metal foil according to any embodiment of the present invention.

[0090] Since the metal-clad laminate includes the composite metal foil provided by any embodiment of the present invention, the metal-clad laminate has the same beneficial effects as the composite metal foil, which will not be described in detail herein.

[0091] An embodiment of the present invention further provides a circuit board, which includes a circuit made of the composite metal foil according to any embodiment of the present invention.

[0092] Specifically, the composite metal foil can be a thermistor copper foil, which is used to bury the thermistor copper foil in a circuit with a line width of micrometer level to make a circuit board. It does not occupy the position where the components of the circuit board are placed, and is combined with a temperature monitoring circuit. By utilizing the changes in voltage and current in the circuit caused by temperature changes, the heat generation of electronic components can be monitored and even feedback adjusted.

[0093] The composite metal foil can be arranged on the circuit and component surface of the circuit board to measure the temperature of the circuit or component. The circuit board of the embodiment of the present invention includes the composite metal foil, which can monitor the temperature of the circuit board to avoid damage to the circuit board due to excessive temperature.

[0094] Since the circuit board includes the composite metal foil provided by any embodiment of the present invention, the beneficial effects of the above-mentioned circuit board and the composite metal foil are the same, which will not be described in detail here.

[0095] The above specific implementations do not constitute a limitation on the protection scope of the present invention. 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 substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite metal foil, characterized in that: include: Resistive layer and conductive layer; The conductive layer is provided with a first surface, the resistance layer is provided on the first surface, the first surface has a trend line in a sliced ​​state, and 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 in the following manner: 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 resistor 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 next sampling point value is retained, otherwise the previous sampling point value is retained. The raised portion is formed on a side of the trend line away from the conductive layer, and the depressed portion is formed on a 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 1, 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 50nm to 500nm.

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 the 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 is in the range of 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 the 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 resistance layer away from the conductive 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 1, characterized in that The temperature rises from 25° C. to 150° C. and then drops to 25° C. for 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 1-13.

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