Electrolytic copper foil pressing plate plate warping prediction method

Abstract

The application discloses a kind of electrolytic copper foil pressing plate plate warping pre-judgment method, specifically includes the following steps: step one, gradient temperature heat treatment: the electrolytic copper foil of each kind of pressing plate to be sampled, cutting, respectively placed in gradient temperature T1, T2, T3 oven heat treatment, after a certain time, sample is removed and cooled to room temperature.Step two, elongation test: the electrolytic copper foil sample after gradient temperature heat treatment is respectively subjected to elongation test, multiple tests take average, obtain the elongation E (T1), E (T2), E (T3) of sample at different temperatures, step three, data processing;Step four, plate warping determination.The application relates to the technical field of electronic material manufacturing.The electrolytic copper foil pressing plate plate warping pre-judgment method can realize the pre-judgment of plate warping problem before pressing plate, thereby guiding the matching method of pressing plate copper foil, accurately avoiding the occurrence of plate warping phenomenon, improving the production qualified rate of copper-clad plate, and creating greater economic benefits for the printed circuit board industry and copper-clad plate industry.

Description

Technical Field

[0001] This invention relates to the field of electronic material manufacturing technology, specifically a method for predicting the warping of electrolytic copper foil pressure plates. Background Technology

[0002] Electrolytic copper foil and insulating substrate (prepreg) are the basic materials for electronic circuit board manufacturing. The copper foil and insulating substrate are combined to form copper clad laminate using a hot pressing method. However, the copper clad laminate often warps after hot pressing, which seriously affects the product qualification rate of copper clad laminate manufacturing and causes significant economic losses.

[0003] Through long-term research, it has been discovered that during hot pressing, electrolytic copper foil undergoes a transformation in grain morphology upon heating, generally transforming from the columnar crystals characteristic of electrolytic copper foil to bulk crystals. This grain transformation process may be the fundamental cause of warping in copper-clad laminates. From a thermodynamic perspective, electrolytic copper foil with numerous fine grains possesses high grain boundary energy, resulting in a high system energy and unstable crystal texture. During hot pressing, the copper foil is heated, and under thermal excitation, the fine grains, such as columnar crystals, undergo crystal structure rearrangement. Some high-energy fine grains are fused with larger grains, becoming lower-energy, larger bulk crystals. During this transformation from small to large grains, grain boundaries decrease, and the overall crystal density increases, thus creating tensile stress from the edges to the center in the planar direction. Because copper is a temperature-sensitive metal, tensile stress generated by grain transformation during copper foil lamination is unavoidable. Therefore, when the tensile stress on both sides of the copper foil is similar, the overall stress is low, and warping will not occur. Conversely, when the tensile stress on both sides differs significantly, the overall stress is high, and warping may occur. However, in reality, it is impossible to determine the amount of tensile stress generated by the copper foil placed on both sides of the insulating substrate, thus making it impossible to predict whether warping will occur after lamination. To minimize warping, sometimes the same copper foil is placed on both sides of the insulating substrate, but warping still occurs in specific areas. This is because uneven heating during multi-layer lamination results in deviations in the actual lamination temperature, and the grain transformation of certain types of copper foil is sensitive to temperature, leading to higher overall stress. Therefore, warping remains an unresolved issue in copper clad laminate (CCL) manufacturing, causing significant losses for both CCL and copper foil manufacturers.

[0004] Through long-term research, we have discovered that copper foil produced using different processing methods does indeed exhibit differences in crystal texture, potentially leading to warping. However, a reliable analytical testing method has yet to accurately predict whether warping will occur. Furthermore, the temperature control of high-temperature hot presses used in copper clad laminate manufacturing is not uniform, resulting in inconsistent warping issues even within the same batch of press samples, leading to temperature variations. Different copper foils exhibit varying degrees of temperature sensitivity, which may explain why warping can still occur even when pressing two identical copper foils together. The recurring problem is the lack of a reliable method to determine the temperature sensitivity of the copper foil being pressed. Currently, the copper clad laminate and printed circuit board (PCB) industries use room temperature and high-temperature elongation rates to assess warping, but these methods are not entirely effective. Therefore, developing a simple and effective analytical testing method capable of accurately predicting warping in copper foil presses is a significant challenge, and an urgent and crucial task.

[0005] Therefore, this invention proposes a method for predicting the warping of electrolytic copper foil pressure plates to solve the aforementioned problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for predicting the warping of electrolytic copper foil pressure plates, thus solving the problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for predicting the warping of an electrolytic copper foil pressure plate, specifically comprising the following steps:

[0008] Step 1: Gradient Temperature Heat Treatment

[0009] Each type of electrolytic copper foil to be pressed was sampled and cut, and placed in ovens with gradient temperatures T1, T2 and T3 for heat treatment. After a specific time, the samples were taken out and cooled to room temperature.

[0010] Step 2, Elongation Test:

[0011] The elongation of the electrolytic copper foil samples after gradient temperature heat treatment was tested. The average value of multiple tests was taken to obtain the elongation E(T1), E(T2), and E(T3) of the samples at different temperatures.

[0012] Step 3: Data Processing

[0013] The temperature elongation E(T) of the two types of electrolytic copper foils A and B (taking A and B as examples) of the plate to be pressed is differentially processed to obtain the elongation difference ΔE(A) of each copper foil combination AB of the plate to be pressed at different temperatures. T1 -B T1 ), ΔE(A T2 -B T2 ), ΔE(AT3 -B T3 The different temperature elongation E(T) of the two types of electrolytic copper foils A and B on the plate to be pressed are processed by temperature difference value processing to obtain ΔE(A) respectively. T2 -B T1 ), ΔE(A T3 -B T2 ), ΔE(B T2 -A T1 ), ΔE(B T3 -A T2 ).

[0014] Step 4: Determine if the board is warped:

[0015] The first step is a matching determination: if the difference in elongation of the two electrolytic copper foils AB at the pressing temperature T2 is ΔE(A T2 -B T2 If the value is greater than or equal to 2%, the copper foil assembly of the plate to be pressed may warp after pressing, and the judgment ends; otherwise, the second step of judgment is required.

[0016] The second step is to determine the temperature sensitivity: the thermal elongation ΔE(A) of the two types of electrolytic copper foils AB on the upper and lower parts of the platen under a gradient temperature. T2 -B T1 ), ΔE(A T3 -B T2 ), ΔE(B T2 -A T1 ), ΔE(B T3 -A T2 If any of the values ​​is ≥3.5%, the copper foil assembly to be pressed may warp after pressing; otherwise, warping will not occur, and the judgment ends.

[0017] Preferably, the gradient temperature range in step one is based on the platen temperature as the midpoint T2, with two temperatures selected above and below it, namely T1 and T3, for a total of three temperatures. The temperature gradient can be 5-15℃, and the heat treatment time is the same as the platen time.

[0018] Preferably, in step two, the sample elongation is tested at room temperature, and the sample at each temperature is tested at least three times. The average value of the results is taken, and the ratio of the range to the average value should be ≤0.3.

[0019] Preferably, in step three, the values ​​for difference processing and temperature difference processing are both taken as absolute values ​​to ensure that all differences are positive.

[0020] Preferably, step four involves two steps. The first step is a matching determination, which assesses the compatibility of the elongation rates of the two electrolytic copper foils. The 2% value is an empirical value, applicable to copper foils with dimensions of 1 meter in both length and width. This value can be adjusted based on actual results after changing the dimensions.

[0021] Preferably, step four involves two steps. The second step is a temperature sensitivity determination, which assesses the sensitivity of the elongation of the electrolytic copper foil to temperature. The 3.5% value is an empirical value, applicable to copper foils with dimensions of 1 meter in both length and width. This value can be adjusted based on actual results after changing the dimensions.

[0022] Beneficial effects

[0023] This invention provides a method for predicting the warping of electrolytic copper foil pressing plates. Compared with existing technologies, it has the following advantages:

[0024] This method for predicting the warping of electrolytic copper foil pressing plates can predict the warping problem before pressing, thereby guiding the matching method of copper foil in the pressing plates, accurately avoiding the occurrence of warping, improving the scientific nature of the copper foil matching scheme, and increasing the production qualification rate of copper-clad laminates. It will create significant economic benefits for the printed circuit board industry and the copper-clad laminate industry. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1 This invention provides a technical solution: a method for predicting the warping of electrolytic copper foil pressure plates, specifically including the following steps:

[0028] Step 1: Gradient Temperature Heat Treatment

[0029] Each type of electrolytic copper foil to be pressed was sampled and cut, and placed in ovens with gradient temperatures T1, T2 and T3 for heat treatment. After a specific time, the samples were taken out and cooled to room temperature.

[0030] Step 2, Elongation Test:

[0031] The elongation of the electrolytic copper foil samples after gradient temperature heat treatment was tested. The average value of multiple tests was taken to obtain the elongation E(T1), E(T2), and E(T3) of the samples at different temperatures.

[0032] Step 3: Data Processing

[0033] The temperature elongation E(T) of the two types of electrolytic copper foils A and B (taking A and B as examples) on the plate to be pressed is processed by differential value processing to obtain the elongation difference ΔE(AT1-BT1), ΔE(AT2-BT2), and ΔE(AT3-BT3) of each copper foil combination AB on the plate to be pressed at different temperatures. The different temperature elongation E(T) of the two types of electrolytic copper foils A and B on the plate to be pressed is processed by differential value processing to obtain ΔE(AT2-BT1), ΔE(AT3-BT2), ΔE(BT2-AT1), and ΔE(BT3-AT2).

[0034] Step 4: Determine if the board is warped:

[0035] The first step is a matching determination: if the difference in elongation of the two electrolytic copper foils AB on the upper and lower plates at the pressing temperature T2 is ΔE(AT2-BT2)≥2%, then the copper foil combination of the plates may warp after pressing, and the determination ends; otherwise, the second step of determination is required.

[0036] The second step is to determine the temperature sensitivity: if any one of the following values ​​of the thermal elongation ΔE(AT2-BT1), ΔE(AT3-BT2), ΔE(BT2-AT1), and ΔE(BT3-AT2) of the two electrolytic copper foils AB on the plate to be pressed is ≥3.5%, then the plate may warp after the copper foil combination is pressed; otherwise, the plate will not warp, and the determination ends.

[0037] Step 1: The gradient temperature range uses the pressing plate temperature as the midpoint T2, with three temperatures selected above and below it (T1 and T3 respectively), for a total of three temperatures. The temperature gradient can be 5-15℃, and the heat treatment time is the same as the pressing plate time. Step 2: The sample elongation is tested at room temperature. Samples at each temperature are measured at least three times, and the average result is taken. The ratio of the range to the average should be ≤0.3. Step 3: The difference processing and temperature difference processing values ​​are all taken as absolute values ​​to ensure that all differences are positive. Step 4: The judgment is divided into two steps. The first step is a matching judgment to evaluate the matching of the elongation of the two electrolytic copper foils. 2% is an empirical value, applicable to copper foil dimensions of 1 meter in both length and width. This can be adjusted based on actual results after changing the dimensions. Step 4: The second step is a temperature sensitivity judgment to evaluate the sensitivity of the electrolytic copper foil elongation to temperature. 3.5% is an empirical value, applicable to copper foil dimensions of 1 meter in both length and width. This can be adjusted based on actual results after changing the dimensions.

[0038] Comparative experiment

[0039] In actual production, we collected a batch of 35μm copper foil from different manufacturers for use in a 180℃ high-temperature pressing process, totaling six master rolls (named A, B, C, D, E, and F). Following the predictive method of this invention, samples were taken from each master roll, with designed temperature gradients T1, T2, and T3 of 173℃, 180℃, and 187℃, and a heat treatment time of 1 hour (consistent with the pressing time). After the samples cooled, the elongation was tested. At least three points were measured for each sample at each temperature, and points with large dispersion were excluded (the range of test results ≤ 0.3). The average elongation was taken, and the results are shown in Table 1.

[0040] Table 1. Sample elongation test results

[0041] A 24.2 25.7 27.0 B 22.7 23.1 23.3 C 24.2 24.6 24.9 D 25.9 26.2 26.6 E 24.1 27.7 29.8 F 31.3 31.4 31.7

[0042] These 6 types of copper foil can be randomly combined to obtain 21 different pressure plate combinations, as shown in Table 2.

[0043] Table 2. Copper Foil Plate Assembly Methods

[0044] A A-A A-B A-C A-D A-E A-F B - B-B B-C B-D B-E B-F C - - C-C C-D C-E C-F D - - - D-D D-E D-F E - - - - E-E E-F F - - - - - F-F

[0045] The results of elongation difference processing and temperature difference processing for the above pressure plate combination are shown in Table 3.

[0046] Table 3. Results of Elongation Rate Data Processing

[0047]

[0048] Based on the experimental results in Table 3, we can analyze the results using the judgment method provided in this paper. Table 3 shows that using the first step of the judgment, we can conclude that AB, AE, AF, BD, BE, BF, CE, CF, DF, and EF may have board warping issues. Using the second step, we can conclude that DE and EE may also have board warping issues. Furthermore, we found that combinations that may have board warping issues according to the first step often yield the same result using the second step. Most board warping issues can be identified through the first step; only a few combinations cannot be identified by the first step but can be identified by the second step.

[0049] These 6 types of copper foil were randomly combined and pressed at 180°C for 1 hour with the same prepreg. The same combination of copper foil was used for each pressing, and 50 CCL sheets were formed at one time. Each copper foil was 1 meter long and 1 meter wide. The experimental results are shown in Table 4.

[0050] Table 4 Results of Pressure Plate Treatment for Plate Warping

[0051]

[0052] Based on the results shown in Table 4, we can see that the experimental results are basically consistent with the predictions made by this method. Furthermore, the greater the deviation of the data processing results from the empirical values ​​during prediction, the higher the proportion of board warping tends to be, showing a positive correlation. The only inaccurate group was group DE, where the initial results were close to the theoretical values, and the warping was only identified in the second step of the judgment. Therefore, this judgment method is more rigorous, can identify the risk of board warping to the greatest extent, and has a high accuracy rate.

[0053] In summary, this invention provides a method for predicting copper foil plate warping. Through a two-step judgment, it can identify copper foil combinations at risk of warping with a high accuracy rate. This can effectively improve the scientific matching of copper foil when using copper clad laminates, reduce the risk of plate warping, thereby improving product qualification rate and reducing losses and risks.

[0054] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0055] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for predicting the warping of an electrolytic copper foil pressure plate, characterized in that: Specifically, the following steps are included: Step 1: Gradient Temperature Heat Treatment Each type of electrolytic copper foil to be pressed was sampled and cut, and placed in ovens with gradient temperatures T1, T2 and T3 for heat treatment. After a specific time, the samples were taken out and cooled to room temperature. Step 2, Elongation Test: The elongation of the electrolytic copper foil samples after gradient temperature heat treatment was tested. The average value of multiple tests was taken to obtain the elongation of the samples at different temperatures, namely E(T1), E(T2), and E(T3). Step 3: Data Processing The temperature elongation E(T) of the two types of electrolytic copper foils A and B on the plate to be pressed is calculated by difference, and the elongation difference ΔE(A) of each copper foil combination AB on the plate to be pressed at different temperatures is obtained. T1 -B T1 ), ΔE(A T2 -B T2 ), ΔE(A T3 -B T3 The different temperature elongation E(T) of the upper and lower electrolytic copper foils A and B of the plate to be pressed are processed by temperature difference value processing to obtain ΔE(A) respectively. T2 -B T1 ), ΔE(A T3 -B T2 ), ΔE(B T2 -A T1 ), ΔE(B T3 -A T2 ); Step 4: Determine if the board is warped: The first step is a matching determination: if the difference in elongation of the two electrolytic copper foils AB at the pressing temperature T2 is ΔE(A T2 -B T2 If the value is ≥2%, then the copper foil assembly of the plate to be pressed may warp after pressing, and the judgment ends; otherwise, the second judgment step needs to be performed. The second step is to determine the temperature sensitivity: the thermal elongation ΔE(A) of the two types of electrolytic copper foils AB on the upper and lower parts of the platen under a gradient temperature. T2 -B T1 ), ΔE(A T3 -B T2 ), ΔE(B T2 -A T1 ), ΔE(B T3 -A T2 If any of the values ​​is ≥3.5%, the copper foil assembly to be pressed may warp after pressing. Conversely, if the board does not tilt, the judgment ends.

2. The method for predicting the warping of an electrolytic copper foil pressure plate according to claim 1, characterized in that: In step one, the gradient temperature range is defined by taking the platen temperature as the midpoint T2, with two additional temperatures, T1 and T3, selected above and below it respectively, for a total of three temperatures. The temperature gradient is 5-15℃, and the heat treatment time is the same as the platen time.

3. The method for predicting the warping of an electrolytic copper foil pressure plate according to claim 1, characterized in that: In step two, the sample elongation is tested at room temperature. The sample at each temperature is tested at least three times, and the average value is taken. The ratio of the range to the average value is ≤0.

3.

4. The method for predicting the warping of an electrolytic copper foil pressure plate according to claim 1, characterized in that: In step three, the values ​​for difference processing and temperature difference processing are all taken as absolute values ​​to ensure that all differences are positive.

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