JP2007232717A - Disk flow system and fluidity evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting the deformation speed of low viscosity resin of quick deformation speed, a disk flow device for automatically calculating relation between the shearing speed and viscosity in the disk flow device, and evaluating fluidity in low shearing region by using the disk flow device. <P>SOLUTION: The disk flow device of non-contact type for calculating the shearing speed and the viscosity of resin comprises: the displacement detection device in position detection resolution is ≤2μm, and the time interval of outputting displacement signal is ≤100ms; and the calculating means of the shearing speed and the viscosity by successively acquiring the output data of displacement signal of measuring resin. The method of evaluating the fluidity of the resign evaluates the fluidity of the resin by the stress value represented by the product of shearing speed and the viscosity at the shearing speed of ≤1s<SP>-1</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a disk flow device and a fluidity evaluation method using the data.

The flow evaluation method, called the disk flow method, measures the change in the height (thickness) of a resin by sandwiching the resin to be measured between two flat plates and applying a desired load to cause the resin to spread in a disk shape. Thus, the fluidity of the resin is evaluated. Therefore, the disk flow method is positioned as a fluidity evaluation method suitable for a resin having a slow deformation speed, that is, an extremely high viscosity (viscosity: 10 ⁴ to 10 ⁶ Pa · s).

  The apparatus is commercialized under the name “parallel plate plastometer” (see Non-Patent Document 1). Since this “parallel plate plastometer” is intended for resins with high viscosity and slow deformation speed, displacement is detected by a contact-type dial gauge at a predetermined time interval (usually in the order of “minutes” to “hours”). ) To measure the change in the height (thickness) of the resin, graph the relationship between the elapsed time and the height (thickness) of the resin, calculate the deformation speed from the graph, and calculate the viscosity of the resin manually. Done in In addition, MFR (melt flow rate) and SR (swelling ratio) of thermoplastic resin are measured simultaneously with one automatic measuring device, so as to eliminate the complexity of MFR and SR measurement. In addition, a method and an apparatus for automatically measuring a swelling ratio have been proposed (see, for example, Patent Document 1).

Therefore, with a conventional disk flow method having a high deformation speed and a low viscosity resin, for example, an epoxy compound for semiconductor encapsulation (high flow type flow tester viscosity: 5 to 50 Pa · s), the deformation speed is accurately set. It is extremely difficult to measure, and calculation of shear rate and viscosity has not been realized. Therefore, in the prior art for the semiconductor sealing epoxy compound, the fluidity is evaluated by the evaluation method shown in FIGS. FIG. 9 is a schematic view showing an application example of a conventional disk flow method to a low viscosity resin. FIG. 10 shows the fluidity evaluation method of FIG. 9, where FIG. 10 (a) is a top view showing the size of the resin disk, and FIG. 10 (b) is a side view of the resin disk of FIG. As shown in FIG. 9, the resin 17 is pressed with a constant load by two heating flat plates 26 a and 26 b to cause a disc-like flow, and after pressing and curing, the magnitude of the disc-like flow of the resin shown in FIG. The diameter 27 of the resin disk is measured, and the fluidity of the resin is evaluated based on the size.
G. J. et al. Dienes and H.C. F. Klemm, “Theory and Application of the Parallel Plate Plasmeter”, Journal of Applied Physics, vol. 17, pp. 458 (1946) JP-A-8-278244

  In the conventional evaluation method based on the resin diameter after flow, the difference in flowability between resins can be evaluated, but a quantitative index relating to stress such as flow resistance cannot be obtained. Therefore, the present invention provides a disk flow device that accurately detects the deformation speed of a low-viscosity resin having a high deformation speed and automatically calculates the relationship between the shear rate and the viscosity in the disk flow. Furthermore, the present invention provides a method for evaluating the fluidity of a low shear region using the disk flow device.

  The present invention relates to (1) and (2) below.

(1) A disk flow device for calculating the shear rate and viscosity of a resin, which is a non-contact type, has a position detection resolution of 2 μm or less, and a displacement signal output time interval of 100 ms or less, and the displacement detection A disk flow apparatus comprising: means for sequentially acquiring data of a displacement signal output of a resin measured from a vessel, and calculating a shear rate and a viscosity from the data.

(2) From the data of the shear rate and the viscosity of the resin obtained by the disk flow device described in the preceding item (1), the stress value represented by the product of the shear rate and the viscosity at a shear rate of 1 s- ¹ or less, A fluidity evaluation method characterized by evaluating the fluidity of a resin.

  According to the present invention, a disk flow device that accurately detects the deformation rate of a low-viscosity resin having a high deformation rate and automatically calculates the relationship between the shear rate and the viscosity in the disk flow, and a low shear using the disk flow device. It has become possible to provide a method for assessing the fluidity of a region.

  In the disk flow method, in order to measure a resin having a low viscosity and a high deformation speed, it is preferable to first reduce the applied load. When the load is reduced, it is preferable that the measurement load does not affect the load condition in the displacement measurement for measuring the resin height (thickness).

  Therefore, in the present invention, a non-contact type displacement meter is employed as the displacement meter. Furthermore, since the deformation speed of the resin is high, it is preferable that the position detection resolution is high and the displacement signal is output at short time intervals, and more preferably output automatically. For example, an electronic displacement meter that satisfies the above can be employed.

  The position detection resolution of the displacement meter according to the present invention is 2 μm or less, preferably 1 μm or less. The time interval of displacement signal output is 100 ms or less, preferably 50 ms or less.

  A laser displacement meter can be employed as an electronic displacement meter that can measure displacement without contact and that automatically outputs a displacement signal at short time intervals. This laser displacement meter detects the displacement of the flat plate by irradiating a laser to the flat plate that pressurizes the resin or the portion connected to it, and reading the position change of the reflected laser. The load by measurement is not applied. The laser displacement meter can measure displacement with a resolution of 2 μm or less and can output a displacement signal every 60 ms of 100 ms or less, which is suitable for measurement of a resin having a low viscosity and a high deformation speed.

  On the other hand, the disk flow device of the present invention further includes means for sequentially acquiring data of the displacement signal output of the resin measured from the displacement detector and calculating the shear rate and viscosity from the data. In calculating the shear rate and viscosity by the disk flow method, the output displacement signal is input to the calculation means such as a personal computer (hereinafter referred to as a personal computer). Thus, the deformation speed is obtained by time differentiation of the displacement, the shear rate and the viscosity are calculated by the following formula (1), and a series of operations for graphing the resin height (thickness), the shear rate, the viscosity and the like are performed. Can be automated.

Regarding the fluidity evaluation method, from the data of the shear rate and the viscosity of the resin obtained as described above, the fluidity of the resin is expressed by the stress value represented by the product of the shear rate and the viscosity at a shear rate of 1 s ⁻¹ or less. It is characterized by evaluating.

A resin system filled with a large amount of filler, such as an epoxy resin compound for semiconductor encapsulation, exhibits a flow behavior as a pseudoplastic fluid and has a yield value τ _y .

The yield value τ _y is a shear stress necessary for the resin to start flowing. Therefore, in the present invention, a stress value “low shear region flow stress” when the shear rate is 1 s ⁻¹ or less is newly defined as a flow stress in place of the yield value from the shear rate and viscosity obtained by the disk flow device. And an index for evaluating the fluidity of the resin.

The “low shear region flow stress” will be described below. First, displacement signal data relating to the resin height (thickness) from the displacement detector is input to a personal computer, and the deformation speed is obtained by taking a time derivative of the displacement data. The following equations (2) and (3) ) [Refer to Non-Patent Document 1] automatically calculates the shear rate and viscosity η as a function of time.

Substituting the relational expression between the shear stress τ and the viscosity η shown in the following formula (4) into the relational expression between the shear stress and the shear rate of the pseudoplastic fluid shown in the previous formula (1), the following formula is obtained. (5) is obtained.

  In the equation (5), if the shear rate is reduced, the second term on the right side may be ignored.

Therefore, the “low shear region flow stress” τ ^* shown in the following formula (6) defined by the product of the shear rate and the viscosity in a low shear region of a shear rate of 1 s ⁻¹ or less is used as a fluidity evaluation index. In particular, the value at the shear rate of 1 s ⁻¹ is defined as “representative / low shear region flow stress” [τ ^* ₁ ] of the resin.

An example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional schematic view showing an example of a disk flow device 1 according to the present invention. FIG. 2 is an enlarged cross-sectional view of the resin pressurization unit and the flow deformation state of the resin of the disk flow device 1 of FIG. The disk flow device 1 includes a base 2 having a circular flat surface portion 4 and a circular flat plate disk 5 for pressurizing the measurement resin 17 above the base 2. The disc 5 has a structure that can move up and down while maintaining parallel to the circular flat portion 4 of the base 2 by the connected shaft 6 and the sleeve of the frame 8 connected to the base 2. The surface of the base 2 that presses the resin between the circular flat portion 4 and the disk 5 is preferably finished to a matte surface having a surface roughness R _{Z of 2 to} 15 μm by electric discharge machining or sandblasting, and further, hard chrome plating or the like It is preferable that anti-wear measures are taken. The base 2 includes an electric heater 3 so that the measurement temperature can be set to a desired temperature. The support 9 of the frame 8 is provided with a heat insulating material 10 made of reinforced plastic so that heat from the base 2 does not affect a laser displacement meter 12 (described later) and the like.

  A laser displacement meter mounting stand 11 is provided on the upper surface of the frame 8, and a laser displacement meter 12 is attached to the stand 11. Laser light 13 is emitted from the laser displacement meter 12 toward the shaft cap 7. The laser beam reflected by the cap 7 is received by the laser displacement meter 12, and the displacement of the cap 7 is detected. Therefore, if the state where the disk 5 is in contact with the circular flat surface portion 4 of the base 2 is the origin (displacement 0 mm) and the upper side displacement is set to a positive value, the displacement of the cap 7 will be the height of the measurement resin ( Thickness).

  The following (1) to (5) are exemplified as the measurement procedure. (1) A tablet of resin 17 for measurement is prepared. (2) Place the tablet on the center of the circular flat surface portion 4 of the base 2 with the disk 5 raised. (3) The disk 5 is lowered until it contacts the upper surface of the tablet, and is stopped and held by the electromagnetic actuator 18. (4) After preheating the tablet, the disk 5 is released from being stopped by the electromagnetic actuator 18 and is naturally lowered in the displacement direction 20. As a result, the resin flows in a disk shape. (5) After the resin 21 after the disc-like flow is cured, the disk 5 is raised to release the cured resin.

  The size of the tablet may be determined from the heat transfer efficiency from the base plane portion 4, the final diameter after flow, and the size of the plane portion 4 and the disk 5. Considering tablet production and heat transfer, a diameter of about 10 to 20 mm and a mass of about 0.5 to 1.5 g are suitable. The measurement temperature (preheating temperature and curing temperature), preheating time, and curing time of the tablet are appropriately set depending on the resin composition. For example, in the case of an epoxy resin composition, the measurement temperature is 170 to 180 ° C., and the preheating time is 5 to 5. 10 seconds and a curing time of about 50 to 100 seconds are preferable.

  The load applied to the resin may be the load of its own weight due to the total mass of the disk 5, the shaft 6 and the shaft cap 7 of the apparatus. May be adjusted.

  The personal computer 16 receives the displacement signal 14 of the disk 5 simultaneously with the stop and release of the disk 5 by the electromagnetic actuator 18. In the personal computer 16, based on the displacement data, a graph of the change in resin height (thickness), shear rate, and viscosity with time is created using a pre-installed calculation formula and graph creation function.

  The displacement signal 14 from the laser displacement meter 12 is synchronized with the holding release signal (measurement start signal 19) of the electromagnetic actuator 18 used for holding the position of the shaft cap 7 to the personal computer 16 via the amplifier 15. Entered.

  Hereinafter, the present invention will be described by way of examples.

Example 1
A disk flow apparatus 1 shown in FIGS. 1 and 2 was prepared. The disk flow device 1 includes a base 2 having a circular flat surface portion 4 and a circular flat plate disk 5 for pressurizing the measurement resin 17 above the base 2. The disk 5 can move up and down while being parallel to the circular flat portion 4 of the base 2 by the connected shaft 6 and the sleeve of the frame 8 connected to the base 2.

The surface of the base 2 that presses the resin of the circular flat portion 4 and the disk 5 is finished to a matte surface having a surface roughness R _{Z of} 6 μm by electric discharge machining, and further subjected to hard chrome plating as a wear countermeasure. used. Moreover, the displacement detection accuracy (resolution) of the laser displacement meter 12 (manufactured by Keyence Corporation, model number LB-02) was 2 μm, and the time interval for transmitting the displacement signal was 60 ms.

Using the above-described disk flow apparatus according to the present invention, the fluidity was measured under the conditions listed in Table 1. The resin system to be measured is an epoxy resin compound for semiconductor sealing (hereinafter referred to as sealing resin), which is “sealing resin A” filled with 90% by mass of silica filler and 85% by mass. Two types of sealing resins of low-viscosity grade “sealing resin B” filled with silica filler were taken up. The measurement temperature is 175 ° C., which is the same as the molding temperature, and the load applied to the resin is a load of 1.86 N based on the total mass of the disk 5, shaft 6 and shaft cap 7 of the apparatus, and a weight of 0.98 N ( 2 conditions with 2.84N added (not shown). The slit viscosity for comparison was measured with a slit type viscosity measuring device manufactured by Hitachi Chemical Co., Ltd. under conditions of a shear rate of 100 s ⁻¹ and a temperature of 175 ° C.

(Measurement Example 1)
The sealing resin A was measured under the conditions of a temperature of 175 ° C. and a load load of 1.86 N.

  The measurement procedure was as follows. (1) A tablet of sealing resin A (diameter 20 mm, mass 1 g) was produced. (2) With the disk 5 raised, the tablet was placed on the center of the circular flat surface portion 4 of the base 2. (3) The disk 5 was lowered until it contacted the upper surface of the tablet, and stopped and held by the electromagnetic actuator 18. (4) After pre-heating the tablet (pre-heating time 5 seconds), the disk 5 was released from the stop-hold state by the electromagnetic actuator 18 and naturally lowered. (5) The resin flowed in a disk shape, and after curing (curing time 60 seconds), the disk 5 was raised to release the cured resin.

  A displacement signal 14 of the disk 5 was input to the personal computer 16 at the same time as the stop and release of the disk 5 by the electromagnetic actuator 18 was released. In the personal computer 16, based on the displacement signal data, a diagram of the temporal change in the resin height (thickness), shear rate, and viscosity was created by using a pre-installed calculation formula and graph creation function.

FIG. 3 shows changes over time in the resin height (thickness) 22a, the shear rate 23a, and the viscosity 24a obtained by this measurement. FIG. 4 illustrates the relationship between the shear rate and the viscosity. From FIG. 3, the change in the resin height (thickness) decreases with the elapsed time, and the resin thickness settles to a constant value. The shear rate also decreases correspondingly. In contrast, the viscosity is increasing. As shown in FIG. 4, this is due to the shear rate dependence of the viscosity. In this case, the flow index n shown in the above equation (1) is close to zero. In general, the shear rate in the disc flow method is smaller than the shear rate of the slit type viscometer, and it can be seen that the disc flow device according to the present invention is suitable for viscosity evaluation at a shear rate of 0.1 to 10 s ⁻¹ .

(Measurement example 2)
Next, with respect to the same sealing resin A as in Measurement Example 1, only the load was changed from 1.86N to 2.84N, and the same measurement was performed. The load load was changed by placing a ring-shaped weight 0.98N on the disk 5 so that the total load was 2.84N. The relationship between the shear rate and the viscosity was determined from the obtained resin height, shear rate, and viscosity data, and is shown in FIG. 5 in comparison with the load of 1.86 N in Measurement Example 1. From FIG. 5, it can be seen that the viscosity characteristics obtained do not change even when the load condition is changed. From this, it can be said that the measurement by the disk flow apparatus according to the present invention is general in practice.

(Measurement Example 3)
It measured on the same conditions as the measurement example 1 using the sealing resin B which is a low-viscosity grade whose filling rate of a silica filler is 85 mass%. In FIG. 6, the time change of resin height (thickness) 22b obtained by the measurement example 3, the shear rate 23b, and the viscosity 24b is shown. Since the sealing resin B has a lower viscosity and better fluidity than the resin A, the amount of deformation is large and the final resin height (thickness) is small. Furthermore, the relationship between the shear rate and the viscosity was determined from the data of FIG. 6 and shown in FIG. From FIG. 7, the viscosity [η ₁ ] at a shear rate of 1 s ⁻¹ was 260 Pa · s for the sealing resin A and 39 Pa · s for the resin B.

  For comparison, Resin A and Resin B were evaluated from the resin diameter after flowing by the conventional low viscosity disk flow method shown in FIGS. As a result, the resin A was 28.7 mm, and the resin B with good fluidity was 41.5 mm.

  According to the present invention, it can be seen that the difference between the two resins appears larger than the difference in slit viscosity and the difference in resin diameter after conventional flow.

(Example 2)
Here, based on the measurement data obtained by the apparatus shown in Example 1, an example of the fluidity evaluation method according to the present invention will be described.

That is, the evaluation method uses “low shear region flow stress” as a fluidity evaluation index. “Low shear region flow stress” is the product of the shear rate and the viscosity, as defined in the above equation (6). FIG. 8 shows the relationship between the low shear region flow stresses 25a and 25b between the sealing resins A and B and the shear rate. This “low shear flow stress” shows a substantially constant value in a low shear region of 1 s ⁻¹ or less. As a representative value of “low shear region flow stress”, a stress value “representative / low shear region flow stress” [τ ^* ₁ ] at a shear rate of 1 s ⁻¹ is shown in Table 2.

  Also from this “representative low shear region flow stress”, the good fluidity of the sealing resin B is clearer than the comparison by the conventional slit viscosity.

  Next, as an application example of the fluidity evaluation method based on “low shear region flow stress” to formability evaluation, deformation of a gold wire in sealing molding of a semiconductor package was evaluated. The gold wire was deformed by a compression (compression) sealing molding method using the sealing resins A and B, and the specification of the gold wire was 15 μm in diameter and 6 mm in length. The main molding conditions were a resin temperature of 175 ° C. and a compression speed of 0.1 mm / s.

  As a result of molding, the wire deformation was as small as about 10% in the case of the sealing resin A and about 2% in the case of the resin B. Here, the deformation rate is a percentage of the arcuate displacement with respect to the span distance of the gold wire. Considering the difference ratio of wire deformation (about 5: 1), it is evaluated by the difference (about 7: 1) of "typical / low shear region flow stress" rather than the difference of conventional capillary viscosity (about 2: 1). It seems that is better for the situation. This is probably because in compression molding, the shear rate of the resin flow with respect to the gold wire is very small, and a yield stress force acts on the gold wire. Therefore, in such sealing molding, it can be said that the “low shear region flow stress” according to the present invention is more suitable as a fluidity index than the conventional slit viscosity.

It is a partial section schematic diagram showing an example of a disk flow device by the present invention. It is sectional drawing which expands and shows the resin pressurization part of the disk flow apparatus by this invention, and the flow deformation state of resin. It is a figure which shows the data of the measurement example 1 by the disk flow apparatus by this invention. It is a figure which shows the relationship between the shear rate of the measurement example 1, and a viscosity. It is a comparison figure of the shear rate of a measurement example 1 and the measurement example 2, and a viscosity. It is a figure which shows the data of the measurement example 3. It is a comparison figure of the viscosity by the fluidity evaluation method by the present invention. It is a figure which shows the low shear area flow stress by the fluidity | liquidity evaluation method by this invention. It is a figure which shows the example of application to the low viscosity resin of the disk flow method by a prior art. It is a figure which shows the fluidity evaluation method by the disk flow method by a prior art, (a) is a top view which shows the magnitude | size of a resin disk, (b) is a side view of the resin disk of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Disk flow apparatus 2 ... Base 3 ... Electric heater 4 ... Plane part on base 5 ... Disk 6 ... Shaft 7 ... Shaft cap 8 ... Frame 9 ... Frame support | pillar 10 ... Heat insulating material 11 ... Stand 12 ... Laser displacement meter 13 ... Laser beam 14 ... Displacement signal 15 ... Amplifier 16 ... Personal computer (PC)
DESCRIPTION OF SYMBOLS 17 ... Resin 18 ... Electromagnetic actuator 19 ... Measurement start signal 20 ... Displacement direction of disk 21 ... Resin 22a, 22b ...
23a, 23b ... Shear rate 24a, 24b ... Viscosity 25a, 25b ... Low shear region flow stress 26a, 26b ... Flat plate 27 ... Size of disk-like flow (diameter of resin disk)

Claims (2)

  A disk flow device for calculating the shear rate and viscosity of a resin, which is a non-contact type, has a position detection resolution of 2 μm or less and a displacement signal output time interval of 100 ms or less, and measurement from the displacement detector A disk flow apparatus comprising: means for sequentially taking in data of displacement signal output of a resin to be calculated and calculating a shear rate and a viscosity from the data. From the shear rate and viscosity data of the resin obtained by the disk flow apparatus according to claim 1, the fluidity of the resin is expressed by a product of the shear rate and the viscosity at a shear rate of 1 s ⁻¹ or less. The fluidity evaluation method characterized by evaluating.

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