JP2014100879A - Hot warpage analysis method for a liquid crystal polymer injection-molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict, in a hot warpage analysis method for a liquid crystal polymer injection-molded article, a warpage deformation arising on an injection-molded article having a three-dimensional orientation distribution in a favorable precision so as to enable the inhibition of the warpage deformation thereof.SOLUTION: The hot warpage of an injection-molded article is calculated through steps of: acquiring, from three-dimensional images provided by X-ray computed tomography (CT), data, within an injection-molded article including a filler, on the three-dimensional orientation of the filler (first step); acquiring mutually associated data on the integrated shear stress value, molecular orientation state (orientation, degree of orientation), and linear expansion coefficient of a filler-free reference sample (second step); acquiring data on the integrated shear stress value and molecular orientation state of the injection-molded article (third step); determining, based on the respective data, data on the linear expansion coefficient of the injection-molded article (fourth step); calculating, by using a homogenizing method based on the respective data on the determined linear expansion coefficient and three-dimensional orientation of the filler, a linear expansion coefficient taking the filler into account (fifth step); and performing structural analyses by using the calculated coefficient (sixth and seventh steps).

Description

  The present invention relates to a method for analyzing a hot warp of a liquid crystal polymer injection molded product.

  Conventionally, liquid crystal polymers have been widely used as small, thin, fine-shaped injection molded products because of their excellent properties such as high fluidity, high elasticity, low linear expansion coefficient, and high heat resistance. Used in electronic parts. In addition, an injection-molded product of liquid crystal polymer called super heat resistant type I is also used for applications exposed to a high temperature of 200 ° C. or higher. Liquid crystal polymer injection molded articles usually have different thermal and mechanical properties depending on the orientation direction of the liquid crystal polymer molecules, and may have a multilayer structure. Such liquid crystal polymer injection-molded products undergo warpage deformation (hot warpage deformation) due to thermal load. Therefore, in order to ensure dimensional accuracy, molding is performed in a manner in which warpage deformation is less likely to occur, and molding. It is important to control the later warping deformation.

  The warpage deformation of the molded product is the shape of the molded product, the mode of liquid crystal polymer flow during molding, the distribution of thermal history to the molded product, the distribution of thermal and mechanical properties such as linear expansion coefficient and Young's modulus in the molded product, In addition, factors such as heat load on the molded product occur in combination. The warp deformation that occurs as a response of the molded product to a thermal load or the like depends on the distribution of thermal properties and mechanical properties of the molded product. Regarding such an injection molded product of liquid crystal polymer, there is known a hot warpage deformation prediction method for predicting warpage deformation of a molded product caused by heating after molding and suppressing warpage deformation (for example, Patent Document 1). reference).

JP 2012-96488 A

  However, the warpage deformation prediction method as shown in Patent Document 1 described above does not correspond to an injection molded product using a composite material in which a fibrous filler is included in a liquid crystal polymer. Due to the need to improve the rigidity of injection molded products with the recent miniaturization and thinning of electronic components, injection molded products are molded from composite materials in which fibrous fillers such as glass fibers are mixed into liquid crystal polymers. The In the case of injection-molded products made of composite materials containing fibrous fillers, the distribution of thermal and mechanical properties such as linear expansion coefficient and Young's modulus in the molded product is the distribution of the amount of fibrous filler at each point in the molded product. It depends on the distribution (orientation distribution) in the longitudinal direction of the fibrous filler. Therefore, it is necessary to perform a hot warp analysis in consideration of the distribution and orientation distribution of the fibrous filler in the molded product. In addition, hot warp analysis requires anisotropy data of the linear expansion coefficient corresponding to the anisotropy distribution at each point of the injection molded product to be analyzed. It is difficult to obtain data on the anisotropy of the linear expansion coefficient at each point because of the small size. This is because measurement of the data of the coefficient of linear expansion requires that the measurement test piece has a certain size or more due to the constraints imposed by the apparatus for measuring the coefficient of linear expansion.

  The present invention solves the above-described problems, and improves the prediction accuracy of warpage deformation occurring in an injection molded product containing a filler having a three-dimensional orientation distribution, and can improve the suppression of warpage deformation. An object is to provide a hot warpage analysis method.

  In order to achieve the above object, the present invention provides a first step of acquiring data of three-dimensional orientation of a filler in an injection-molded product including a filler in a method for analyzing hot warpage of a liquid crystal polymer injection-molded product, and a filler. For reference samples injection-molded with liquid crystal polymer not included, data on integral values of shear stress due to flow and solidification during molding, data on molecular orientation, and data on linear expansion coefficient related to these data The second step of acquiring the data of the integral value of the shear stress resulting from the flow and solidification during the molding and the data of the molecular orientation state, the second step and the second step Based on the data acquired in the three steps, the fourth step for determining the data of the linear expansion coefficient for the injection molded product, and the filler acquired in the first step Based on the three-dimensional orientation data and the linear expansion coefficient data determined in the fourth step, the fifth step for obtaining the linear expansion coefficient in consideration of the filler using the homogenization method and the linear expansion obtained in the fifth step The sixth step of mapping coefficient data to each element of the finite element model for structural analysis of injection molded products, and the structural analysis using the finite element method model in which the linear expansion coefficient data is mapped by the sixth step And a seventh step of calculating the expansion and contraction generated in each element when the temperature of the injection-molded product is changed and analyzing the hot warpage of the injection-molded product.

  In this hot warpage analysis method, in the first step, data of the three-dimensional orientation of the filler may be acquired from the three-dimensional image of the filler in the injection molded product acquired using X-ray CT.

  In this hot warpage analysis method, the shape and arrangement of individual fillers in a three-dimensional image are acquired by image processing using a Monte Carlo method that is determined by randomly changing the shape and arrangement of a model representing the filler, You may acquire the data of the three-dimensional orientation of a filler.

  According to the hot warpage analysis method of the liquid crystal polymer injection molded article of the present invention, the linear expansion coefficient considering the filler is obtained using a homogenization method, and the structural analysis is performed using the linear expansion coefficient. It is possible to improve the prediction accuracy of warpage deformation occurring in an injection molded product. Also, since the linear expansion coefficient anisotropy data for the injection-molded product is determined based on the locally measurable integral value of the shear stress and the molecular orientation state data, the injection-molded product has a small size. However, necessary data can be obtained and hot warpage analysis can be performed.

The flowchart about the hot warp analysis method of the liquid crystal polymer injection-molded article which concerns on one Embodiment of this invention. The figure explaining the same analysis method. (A) is a diagram qualitatively showing the dependency of the linear expansion coefficient used in the analysis method on the degree of molecular orientation in the injection-molded product with respect to the orientation direction of the molecular orientation and the direction orthogonal to the orientation, and (b) is the same analysis. The figure which shows the shear stress integral value dependence about the injection-molded product of the linear expansion coefficient used in a method qualitatively about the orientation direction of a molecular orientation, and an orientation orthogonal direction. (A) is a top view which shows typically the orientation measurement position in the injection molded product of hot warp analysis object, (b) shows the orientation and orientation degree in the orientation measurement position of (a) by the inclination and length of the arrow. Plan view. The top view which shows typically the anisotropic distribution of the linear expansion coefficient in the injection molded product of the same hot warpage analysis object. The perspective view which shows a linear expansion coefficient anisotropic distribution typically by mapping a linear expansion coefficient to the element of a finite element model. (A) is a plan view of an injection molded product that is an object of the embodiment of the analysis method, (b) is a side view of the injection molded product, (c) is a cross-sectional view taken along line AA in (a), and (d). FIG. 3 is a perspective view showing a test piece set in the injection molded product. (A) is a diagram showing a three-dimensional image by X-ray CT of the entire test piece shown in FIG. 7 (d), (b) is a three-dimensional image in which a filler model extracted from the image is superimposed on the image and displayed. FIG. The graph of the integration frequency of the filler length about the filler extracted from each of the same test piece. The graph which shows the orientation distribution about the filler extracted from each of the same test piece with an integrated frequency. The scatter diagram which shows the measured value and calculated value of the amount of hot warpage change of an injection molded product about the same analysis method and a comparative example.

  Hereinafter, a hot warp analysis method for a liquid crystal polymer injection-molded product according to an embodiment of the present invention will be described with reference to the drawings. 1 to 5 show a hot warpage analysis method (hereinafter referred to as an analysis method) of a liquid crystal polymer injection-molded product containing a filler. In this analysis method, as shown in FIGS. 1 and 2, the hot warpage of the injection-molded product is analyzed by the structural analysis using the finite element method model from the first step (S1) for acquiring the three-dimensional orientation data of the filler. 7 steps (S1 to S7) up to the seventh step (S7). The execution order of each of these seven steps is not limited to the order shown in FIG. 1, and as shown in FIG. The mutual execution order of the steps can be appropriately changed. Hereinafter, each process is demonstrated in order.

  The first step (S1) is a step of acquiring three-dimensional orientation data of the filler in the injection-molded product, and the data is, for example, the three-dimensional filler of the injection-molded product acquired using X-ray CT. It can be acquired from the image. In this case, data acquisition can be performed by image processing using a Monte Carlo method in which the shape and arrangement of individual fillers in a three-dimensional image are determined by randomly changing the shape and arrangement of a model representing the filler. .

  The second step (S2) is a step of acquiring data shown in FIGS. 3 (a) and 3 (b). That is, in this second step (S2), with respect to a reference sample injection-molded with a liquid crystal polymer without including a filler, data on the integral value of shear stress resulting from flow and solidification during molding, and data on the molecular orientation state , And linear expansion coefficient data are obtained in association with each other. Here, the molecular orientation state is a term that expresses the degree of orientation and orientation of the liquid crystal polymer molecules together, and the degree of orientation represents the degree of alignment of the longitudinal direction (angle) of a number of molecules in a certain region. It is an index, and the orientation represents the direction in which the directions of those molecules are aligned most.

  The data of the linear expansion coefficient shown in FIG. 3A is related to the data of the molecular orientation state of the liquid crystal polymer molecules in the injection molded product. In the case of this analysis method, anisotropy of the linear expansion coefficient corresponding to the orientation of the liquid crystal polymer molecules occurs in the liquid crystal polymer injection molded product. As shown in FIG. 3A, the linear expansion coefficient decreases in the molecular orientation direction MD as the degree of molecular orientation increases, and in the orientation orthogonal direction TD, which is a direction orthogonal to the molecular orientation direction MD, It shows a tendency to increase as the degree increases. In addition, the linear expansion coefficient in the alignment orthogonal direction TD shows a larger value than the linear expansion coefficient in the alignment direction MD.

  Further, for example, as shown in FIG. 3B, the data of the linear expansion coefficient is associated with data of an integral value of shear stress, which is a temporal integral value of shear stress generated during the injection molding of the liquid crystal polymer. The increase and decrease of each linear expansion coefficient in the orientation direction MD and the orientation orthogonal direction TD with respect to the magnitude of the shear stress integral value has the same tendency as the increase and decrease of each linear expansion coefficient in the orientation direction MD and the orientation orthogonal direction TD with respect to the strength of the molecular orientation described above. Show. This is because the degree of molecular orientation of the liquid crystal polymer molecules in the injection-molded product and the integral value of shear stress during injection molding are closely related to each other. For example, this is also due to the fact that the molecular orientation state is manifested by shear stress generated in the liquid crystal polymer during flow and solidification during molding by injection of the liquid crystal polymer into the mold. Accordingly, in the acquisition of the data in the second step (S2), the data on the molecular orientation of the liquid crystal polymer molecules in the injection molded product and the data on the integrated value of the shear stress at the time of injection molding can be replaced by the other data. In some cases, only one of these data can be acquired.

  Data acquisition will be specifically described. In the second step (S2), the reference sample prepared for obtaining the material properties formed by using the injection-molded product made of the liquid crystal polymer containing no filler is associated with the integral value of the shear stress and the molecular orientation state data. As the data, linear expansion coefficient data is measured. The reference sample for measuring the linear expansion coefficient data is a sample whose shear stress integral value data or molecular orientation state data is known or known, and is prepared regardless of the shape of the injection molded product subject to warpage analysis. can do. The data of the linear expansion coefficient is measured for each of the molecular orientation direction and the molecular orientation orthogonal direction in the reference sample, for example, using a thermomechanical analyzer (TMA). The reference sample is desirably one in which the molecular orientation state is uniformly distributed within a range where the measurement of the linear expansion coefficient is performed, and such a reference sample can be prepared relatively easily.

  Acquisition of molecular orientation state (orientation, degree of orientation) data for reference samples, for example, a microwave molecular orientation meter, a measurement method using a transmission wide-angle X-ray, a measurement method based on the polarization intensity of transmitted light, or any other arbitrary It can be performed by measurement using the measurement method. Further, the data of the integrated value of the shear stress is acquired by calculation using a three-dimensional resin flow analysis software based on computer aided engineering (CAE). The shear stress of the liquid crystal polymer at the time of injection molding changes in each space in the mold every moment while the liquid crystal polymer solidifies while flowing in the mold. Each molecule of the liquid crystal polymer receives a shearing force, and the alignment state at the final stop position is determined according to the time when the force is received. Therefore, the data of the shear stress integral value obtained by integrating the shear stress over time is data representing the molecular orientation state.

  In the third step (S3), for an actual injection-molded product of a liquid crystal polymer containing a filler for analyzing warp deformation, data on the integrated value of shear stress resulting from flow and solidification during molding, and data on the molecular orientation state Is acquired as closely as possible to reflect local anisotropy. Data acquisition of this process is possible even if the data is acquired so that local anisotropy can be reproduced by using an injection molding product for analysis equivalent to the injection molding product instead of the actual injection molding product. Good. The equivalent injection-molded product for analysis is such an injection-molded product in which occurrence of hot warpage equivalent to that in the actual injection-molded product can be found by this analytical injection-molded product. .

  The molecular orientation state data is obtained by measurement. The measurement can be performed using, for example, a test piece TP cut out from an injection molded product as shown in FIG. 4A, or can be performed using the injection molded product as it is. In order to acquire local molecular orientation state data, for example, a measurement method using transmission wide-angle X-ray diffraction with a measurement diameter of 300 μm is used. The degree of molecular orientation is calculated from the half width of the orientation peak appearing in the Debye ring obtained by transmission wide-angle X-ray diffraction. By measurement by such X-ray diffraction, it is possible to obtain molecular orientation state (orientation, degree of orientation) distribution data with a resolution about the measurement diameter. From the measurement data at a large number of local measurement points in a large number of test pieces TP cut out in multiple layers from the injection molded product, three-dimensional data of the molecular orientation state can be acquired for each internal point of the injection molded product. For example, as shown in FIG. 4B, the molecular orientation state data is acquired at each measurement point. In this figure, the orientation is indicated by the direction of the vector, and the degree of orientation is indicated by the length of the vector. In FIG. 4B, the molecular orientation state data is displayed two-dimensionally in a plane, but the vector representing the actual molecular orientation data is a vector in a three-dimensional space. Data is also acquired as data in such a three-dimensional space.

  As with the case of the above-described second step (S2), three-dimensional resin flow based on computer aided engineering (CAE) is used for the integral value of the shear stress for the actual injection molded product or the injection molded product at the design stage. Obtained by calculation using analysis software. The data of the integrated value of the shear stress can be expressed by, for example, a three-dimensional space vector in which the orientation direction MD based on the flow direction of the resin is a vector direction and the integrated value of the shear stress is the magnitude of the vector. The direction of the three-dimensional space vector can be a direction in which the flow direction of the resin is corrected based on various conditions.

  The fourth step (S4) is a step of determining linear expansion coefficient data for the injection-molded product based on the data acquired in the second step (S2) and the third step (S3). For example, when the degree of molecular orientation is used as a characteristic representing anisotropy, the linear expansion coefficient in each direction of the orientation direction MD and the orientation orthogonal direction TD at a certain point of the injection molded product is obtained by using the value of the degree of orientation at that point. These can be determined by reading from the graph of FIG. Further, when using the data of the integral value of the shear stress, it can be similarly determined by reading the linear expansion coefficient in each of the orientation direction MD and the orientation orthogonal direction TD from the graph of FIG. . Thus, as shown in FIG. 5, the linear expansion coefficient of each point in an actual injection molded product is determined.

  The fifth step (S5) uses a homogenization method based on the three-dimensional orientation data of the filler obtained in the first step (S1) and the linear expansion coefficient data determined in the fourth step (S4). This is a step of obtaining a linear expansion coefficient in consideration of the filler. The calculation of the homogenization method can be performed by using a general commercial calculation service, using commercially available software, or configuring a program. As the principle of the homogenization method, for example, the Mori-Tanaka theory can be used.

  As shown in FIG. 6, the sixth step (S6) is a step of mapping the linear expansion coefficient data obtained in the fifth step (S5) to each element of the finite element model for structural analysis of the injection molded product. is there. This can be performed by a general data mapping method using various existing structural analysis software and tools.

  The seventh step (S7) is a step of performing structural analysis using the finite element method model in which the linear expansion coefficient data is mapped in the sixth step (S6). In this step, the hot warpage of the injection molded product is obtained by calculating the expansion and contraction that occurs in each element when the temperature of the injection molded product is changed.

  According to this analysis method, the linear expansion coefficient considering the filler is obtained using the homogenization method, and the structural analysis is performed using the linear expansion coefficient. Therefore, the prediction accuracy of the warp deformation occurring in the injection-molded product containing the filler is improved. It can be improved. Also, since the linear expansion coefficient anisotropy data for the injection-molded product is determined based on the locally measurable integral value of the shear stress and the molecular orientation state data, the injection-molded product has a small size. However, necessary data can be obtained and hot warpage analysis can be performed.

(Example)
7 to 11 show an embodiment. As shown in FIGS. 7 (a) and 7 (b), the injection molded product 1 subjected to warp analysis is a long box-shaped molded product having a length of 17.8 × width 1.83 × height 0.4 mm. In the AA cross section, the bottom surface thickness is 0.12 mm, and the side surface thickness is 0.163 mm. The injection-molded product 1 was obtained by injection molding using a pre-plastic injection molding machine with a maximum clamping force of 196 kN using, as a molding resin, an I-type liquid crystal polymer added with glass fibers having an average fiber length of 88 μm as a filler. Molding resin is injected into the longitudinal direction end of the molded product from a position indicated by a pin gate with an arrow. The molecular orientation of the liquid crystal polymer and the orientation of the filler (glass fiber) are globally along the longitudinal direction of the molded product, which is almost the flow direction of the resin. Depending on the degree of spread, the position of the corners, the temperature distribution, etc., various orientation distributions are obtained.

  Test pieces TP1 to TP4 shown in FIGS. 7C and 7D are test pieces for explaining an example of acquiring three-dimensional orientation data of the filler. In other words, in this example, the three-dimensional orientation data (position, fiber length, orientation) of the filler was obtained from the three-dimensional image of the filler in the injection molded product 1 obtained using microfocus X-ray CT. Fig.8 (a) shows the three-dimensional image by X-ray CT of the part of test piece TP1-TP4. For filler orientation, a filler candidate portion is cut out from a three-dimensional image by threshold processing, and a virtual cylinder (filler model) having parameters of length and diameter is fitted to each of a large number of fillers included in the filler candidate portion. It was confirmed and acquired. The fitting of the virtual cylinder to the filler candidate portion was performed using the Monte Carlo method in which the parameters are changed randomly. FIG. 8B shows a virtual cylinder superimposed on the position of the fitted filler.

  FIG. 9 shows the cumulative frequency of the filler length for the filler extracted from each of the test pieces TP1 to TP4. The test pieces TP1 and TP2 on the side surface portion contain relatively long fillers, but the test pieces TP3 and TP4 on the bottom surface portion contain almost no filler of 200 μm or more. Possible causes include interference due to the cavity shape and filler breakage. Since the anisotropy of the liquid crystal polymer is usually influenced by the filler filling amount, it is considered that such a filler inflow inhibition phenomenon in the thin portion of the bottom portion affects the warp analysis accuracy.

  FIG. 10 shows the orientation distribution regarding the filler extracted from each of the test pieces TP1 to TP4 in terms of cumulative frequency. The filler is divided into 0.1 × [rad] by dividing the orientation of the filler extracted in the range of each test piece TP1 to TP4 by 0.1π [rad] for each of the θ axis and φ axis of the spherical coordinates, The orientation was determined in a three-dimensional space. FIG. 10 shows an orientation angle distribution when the orientation in the three-dimensional space is viewed on a wide two-dimensional plane in each of the test pieces TP1 to TP4. As indicated by the arrows in the figure, the global flow direction of the molding resin is 0.5π [rad], and the orientation main axis of the filler is not greatly deviated. It can be seen that the degree of orientation (the degree of alignment) in each of the test pieces TP1 to TP4 is different from each other depending on the position of each of the test pieces TP1 to TP4 in the injection molded product 1.

  FIG. 11 shows the calculated value (□) of the hot warpage change amount obtained by the present analysis method and the calculated value (▲) of the hot warp change amount obtained by the calculation method of the comparative example for the injection molded product 1. The scatter plot with the horizontal axis as the measured value and the vertical axis as the calculated value is shown for two samples. The calculated value (▲) of the comparative example is a calculation result by a calculation method that does not use the homogenization method and does not consider the orientation distribution of the filler. The calculated value (□) of this analysis method is a homogenization method based on the three-dimensional filler arrangement information (position, fiber length, orientation) and the anisotropy of the linear expansion coefficient at each position in the injection molded product 1. This is the result of obtaining the amount of change in hot warp by structural analysis using the anisotropy of the obtained linear expansion coefficient. In this embodiment, the filler orientation is quantitatively evaluated in three dimensions, but the molecular orientation state of the liquid crystal polymer is evaluated only in the two-dimensional transmission direction of X-ray diffraction. The calculation by the homogenization method was performed using commercial non-linear multi-scale material modeling software ((e-Xstreamengeneering Digimat)) and the Mori-Tanaka model. The deformation state was calculated and calculated with respect to the heat load (temperature raised from 25 ° C. to 275 ° C.) As shown in FIG. 11, according to this analysis method, the deformation was obtained by a homogenization method that quantitatively considered the filler orientation. It can be seen that by considering the anisotropy of the linear expansion coefficient, the accuracy of the absolute value is improved as compared with the comparative example not considering the anisotropy of the linear expansion coefficient.

  The present invention is not limited to the above-described configuration, and various modifications can be made. For example, the three-dimensional orientation data of the filler is not limited to being acquired from three-dimensional image data obtained by X-ray CT, and can be acquired from, for example, MRI image data, optical CT image data, and other image data. . Moreover, you may make it acquire the data of the three-dimensional orientation of a filler not based on image data.

1 Injection molded product G0 X-ray CT image (3D image)
MD orientation direction TD orientation orthogonal direction

Claims (3)

In the hot warp analysis method for liquid crystal polymer injection molded products,
A first step of acquiring three-dimensional orientation data of the filler in the injection-molded product including the filler;
For reference samples injection molded with liquid crystal polymer without filler, data on integral values of shear stress due to flow and solidification during molding, data on molecular orientation, and linear expansion coefficient associated with these data A second step of acquiring the data of
For the injection molded product, a third step of acquiring data on the integrated value of shear stress resulting from flow and solidification at the time of molding, and data on the molecular orientation state;
A fourth step of determining data of a linear expansion coefficient for the injection molded product based on the data acquired in the second step and the third step;
A fifth step of obtaining a linear expansion coefficient in consideration of the filler using a homogenization method based on the three-dimensional orientation data of the filler obtained in the first step and the linear expansion coefficient data determined in the fourth step; ,
A sixth step of mapping linear expansion coefficient data obtained in the fifth step to each element of a finite element model for structural analysis of an injection molded product;
By performing structural analysis using the finite element method model in which linear expansion coefficient data is mapped in the sixth step, the expansion and contraction that occurs in each element when the temperature of the injection molded product is changed is calculated. And a seventh step of analyzing the hot warpage of the injection-molded product. A method of analyzing a hot warp of a liquid crystal polymer injection-molded product, comprising:   2. The liquid crystal polymer injection molding according to claim 1, wherein the first step acquires data of a three-dimensional orientation of the filler from a three-dimensional image of the filler in the injection molded product acquired using X-ray CT. Analysis method for hot warpage of products.   By acquiring the shape and arrangement of the individual fillers in the three-dimensional image by image processing using a Monte Carlo method in which the shape and arrangement of the model representing the filler are determined at random, thereby determining the three-dimensional orientation of the filler. The method for analyzing a hot warp of a liquid crystal polymer injection-molded product according to claim 2, wherein data is acquired.

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