CN105271786A - Low-dielectric-constant glass fiber composite material and preparation method thereof - Google Patents

Abstract

The invention relates to a low-dielectric-constant glass fiber composite material and a preparation method thereof. The composite material is prepared by filling epoxy resin with glass fiber. The glass fiber is composed of, in percent by weight, 51%-52% of SiO2, 20%-25% of B2O3, 10%-15% of Al2O3, 2%-6% of CaO, 2%-6% of MgO, 0.15%-0.3% of Na2O, 0-0.3% of K2O, 0-0.3% of Li2O, 0-0.9% of CaF2, 0-2% of TiO2, and 0-0.5% of ZrO2. The composite material possesses relatively good dielectric property, and possesses the dielectric constant of about 4.5 under 1 MHz. Also, the raw material cost is low, subsequent processing is easy, and the composite material is applicable as an enhanced material for a substrate of a printing circuit, and possesses relatively large commercial prospect.

Description

A kind of glass fiber composite material with low dielectric constant and preparation method thereof

technical field

The invention belongs to the field of glass fiber composite material and its preparation method, in particular to a glass fiber composite material with low dielectric constant and its preparation method.

Background technique

As digital technology gradually penetrates into every aspect of daily life, many high-frequency applications are getting closer and closer to ordinary consumers. Higher frequencies mean higher electron propagation speeds, and thus stricter requirements on circuit board substrates. The dielectric constant is the ratio of the capacitance of a certain dielectric capacitor to the capacitance of a capacitor of the same structure in a vacuum state, commonly expressed by ε. If ε is large, it means that the stored electric energy is large, and the signal propagation speed in the circuit will be lower; if ε is small, the electrical signal propagation speed will be faster. Usually, the current direction of the current signal on the printed circuit board is alternately positive and negative. Such frequent exchange is equivalent to the process of "charging-discharging-charging". In the exchange, as long as there is a small amount of capacitance remaining, the transmission speed will be affected, and the energy lost will increase with the increase of the dielectric constant.

For circuit board substrates, several parameters are important. First, the minimum physical property requirements must be met, with suitable machinability for cutting and drilling microvias; second, the dielectric constant must meet the needs of the use, because they determine the energy loss of the substrate.

Electronic glass fiber is an alkali-free glass fiber of aluminoborosilicate system, which has the characteristics of high tensile strength, good electrical insulation performance, good heat resistance and corrosion resistance, and is widely used in substrate materials in the electronics industry. Low dielectric constant glass fiber is just a kind of electronic glass fiber. In recent years, due to the technological progress of the IT industry, as well as the rapid development of computers, mobile phones and other electronic products, it is estimated that the global electronics industry has a low The demand of the dielectric glass fiber and products industry will maintain high-speed growth, and the annual demand growth rate will reach 18.6%. The rapid development of the electronic information industry has put forward higher requirements for glass fiber and electronic cloth, copper clad laminate (CCL), and printed circuit board (PCB). On the one hand, the improvement of product performance requires high-frequency, high-fidelity, and high-security signal transmission; on the other hand, the increase in product functions requires copper-clad laminates to not only serve as substrates, but also to undertake the function of signal transmission lines and control the accuracy of characteristic impedance. Function, function as a built-in passive component in a multi-layer board, etc. The continuous high frequency has pushed the low dielectric constant of PCB to the limit. The space for reducing Dk by improving the resin and molding process is very limited, and it is urgent to reduce the dielectric constant of glass to meet the new requirements.

Through the literature and experimental summary, it is found that the electrical properties and working parameters of the glass cannot be both, that is, when the electrical properties meet the requirements, the fiber-forming temperature of the glass is too high due to the low content of alkali metal and alkaline earth metal ions; on the contrary, in order to make the glass With a suitable fiber-forming temperature, when the content of alkali metal and alkaline earth metal ions in the glass is increased, the electrical properties are affected again. Coupled with technical problems such as glass phase separation and boron volatilization, it hinders the practical application of low dielectric constant electronic glass fibers.

Aiming at the existing problems, domestic and foreign workers have also launched a series of research. Han Lixiong and others mentioned in "High Performance Glass Fiber Characteristics and Research Status" that the early low dielectric constant glass fiber is also called D glass, and its main composition is about 73% SiO ₂ , 22% B ₂ O ₃ , 3 % _R2O . The dielectric properties of D glass fiber are very good. At 10GHz frequency, its dielectric constant is about 4.1, while the dielectric constant of E glass is about 6.6 under the same conditions. However, the forming temperature of D glass is as high as above 1400°C, so it is difficult to melt and form, the production is too difficult, and the cost is very high. Moreover, the drillability, heat resistance, and water resistance of the product CCL are poor, so it is difficult to be widely used in printed circuit boards.

CN101012105A discloses a glass fiber with low dielectric constant, and its optimal ratio is: expressed in weight percent, SiO ₂ 52%-57%, Al ₂ O ₃ 6%-9.5%, B ₂ O ₃ 30.5%-35% %, Na ₂ O0-0.3%, K ₂ O0-0.3%, Li ₂ O0-0.3%, CaO 0-2.5%, MgO 0-2.5%, ZnO 0.5%-2.5%, TiO ₂ 0.5%-3%. The glass fiber manufactured by adopting the composition ratio provided by the invention has better dielectric properties. At room temperature, when the frequency is 1MHz, the dielectric constant is 3.9-4.4, and the drawing temperature is basically not higher than 1350°C. However, the proportion _of B2O3 in the _formula provided by the invention is too high, which will easily cause glass phase separation, and the volatilization amount is too large, which will easily cause filament breakage during the spinning process, which is not conducive to industrial continuous production.

CN101594987A also discloses a glass fiber with low dielectric constant, which contains SiO ₂ 52%-60%, Al ₂ O ₃ 11%-16%, B ₂ O ₃ 20%-30%, CaO 4% by weight ~8%, substantially free of MgO, Li ₂ O, Na ₂ O, K ₂ O and TiO ₂ , may also contain up to about 2% by weight of CaF ₂ ; Containing MgO, in order to avoid the increase of the dielectric constant of the glass composition and the decrease of the water resistance of the glass composition, basically free of Li ₂ O, K ₂ O and Na ₂ O, while avoiding the chemical persistence of the glass fiber caused by phase separation The reduction is substantially free of TiO ₂ . However, it is difficult for the glass fiber disclosed in this invention to achieve the coordination and unification of dielectric properties and drawing temperature. When the dielectric constant is less than 4.5, the drawing temperature is often high, and when the drawing temperature is lowered, the dielectric constant will not meet the requirements.

CN101696089A relates to a low-dielectric constant glass fiber used for high-frequency high-density circuit boards, the optimal composition and the weight percentage of each component include: SiO ₂ 50%-55%, Al ₂ O ₃ 12.7%-15.6% , CaO0.02～0.08%, MgO1.0%～1.9%, ZnO0.5%～1.3%, B2O3 ₂₂ %～ ₂₆ %, _Li2O0.07 %～0.18%, _Na2O0.05 % ~ 0.17%, TiO ₂ 0.4% ~ 2.1%, CaF ₂ 0.8% ~ 2.3%, CeO ₂ 0.25% ~ 0.5%; the glass fiber provided has low dielectric constant, and is easy to produce, good water resistance, and resin Good focus, easy to follow-up processing, etc., but the drawing temperature is too high.

Contents of the invention

The technical problem to be solved by the present invention is to provide a glass fiber composite material with low dielectric constant and its preparation method. The composite material is composed of glass fiber filled epoxy resin, has a low dielectric constant, and is suitable as a printed circuit Substrate material. Filled glass fiber has lower drawing temperature and higher strength, which is suitable for industrial continuous production.

A glass fiber composite material with low dielectric constant of the present invention, the composite material is composed of glass fiber filled epoxy resin; wherein, the weight ratio of glass fiber to epoxy resin is 2-4:10.

The composition of the glass fiber includes: SiO ₂ 51%-52%, B ₂ O ₃ 20%-25%, Al ₂ O ₃ 10%-15%, CaO2%-6%, MgO2%-6%. , Na ₂ O 0.15%-0.3%, K ₂ O 0-0.3%, Li ₂ O 0-0.3%, CaF ₂ 0-0.9%, TiO ₂ 0-2%, ZrO ₂ 0-0.5%.

The sum of the weight percentages of CaO and MgO is 8%.

The weight percent of Na ₂ O, K ₂ O and Li ₂ O satisfies: Na ₂ O+K ₂ O+Li ₂ O=0.3%～0.6%, wherein, Na ₂ O=K ₂ O or Na ₂ O= K2O _{+ Li2O} .

The weight percentage of the CaF ₂ is 0.9%.

The weight percentage of the TiO ₂ is 2%.

The weight percent of the ZrO ₂ is 0.5%.

The spinning temperature of the glass fiber is 1340-1350° C., and it can be drawn continuously.

The tensile strength of the glass fiber is equivalent to that of the alkali-free glass fiber.

When the frequency of the composite material is 1MHz, the dielectric constant is about 4.5, which is more than 30% lower than that of the composite material filled with the same amount of alkali-free glass fiber.

A kind of preparation method of the glass fiber composite material with low dielectric constant of the present invention, comprises:

(1) Weigh the components of the glass fiber, put them in a crucible after mixing, melt at 1500-1550°C for 6-8 hours, and quench to obtain cullet; add the cullet to the crucible of the glass fiber monofilament test line, 1340 ～1350℃ secondary melting for 0.5～1h, wire drawing to obtain glass fiber, take 0.5～1g of glass fiber and spread it in the mold, put it into a 50℃ oven for preheating;

(2) Get epoxy resin and curing agent and mix by mass ratio 10:1, stir, ultrasonic, leave standstill; Then join in the mold of step (1), solidify, obtain the glass fiber composite material with low dielectric constant; Wherein, the weight ratio of glass fiber and epoxy resin in the mold is 2-4:10.

Preheating in the step (1) is carried out in an oven to remove surface air bubbles.

The stirring time in the step (2) is 10 minutes, stirring to a slightly exothermic liquid state; the ultrasonic time is 5 minutes, and the standing time is 30 minutes to eliminate the bubbles generated during the stirring process.

The curing process in the step (2) is to keep the temperature at 50°C for 0.5h, 80°C for 2h, and 120°C for 4h in a vacuum oven.

Among the glass fiber components, SiO ₂ is a glass former and forms a glass network structure. When the content of SiO ₂ is too small, the general dielectric constant is large, and the water resistance and chemical stability of the glass fiber will decrease. When the SiO ₂ content is too much, it is not conducive to the melting and clarification of the molten glass, and the spinning temperature is too high.

B ₂ O ₃ is also a network former, which has good fluxing properties and can reduce the high-temperature viscosity of glass. When B ₂ O ₃ is less, the fluxing effect is reduced, which is not conducive to the melting of glass. If the content is too high, the chemical stability of the glass fiber will be deteriorated due to volatilization and other reasons.

Al ₂ O ₃ is a network intermediate, which mainly plays the role of inhibiting glass devitrification and improving the chemical stability of glass. If the content is too small, the dielectric constant of the glass fiber will be too large, and the water resistance will be poor. When the content is too much, the high-temperature viscosity of the glass liquid is too high, and wire breakage is likely to occur during the wire drawing process.

Both CaO and MgO are exosomes of the network. They cannot form glass alone and do not participate in the network. The main function is to provide additional oxygen ions. The introduction of CaO and MgO can reduce the high-temperature viscosity of the glass and improve the stability of the glass. Generally, if CaO+MgO is too small, it will not work; if the content is too high, the dielectric constant of the glass fiber will be high.

Na ₂ O, K ₂ O, and Li ₂ O are also network exosomes, which can effectively reduce the melting temperature and drawing temperature of the glass, but the damage to the glass network structure is also very significant, affecting the dielectric properties, and need to be properly introduced.

_TiO2 acts to reduce the viscosity, which helps the glass to melt. However, if it is too much, it will cause crystallization and the dielectric constant will increase.

F ^- has the effect of melting and clarifying the glass, reducing the melting temperature and time, but if added too much, the chemical stability of the glass will deteriorate.

On the basis of not reducing the basic performance of glass, ZrO ₂ introduces some auxiliary components to help melting and clarification, and can also increase the strength of glass fiber.

Beneficial effect

(1) The composite material of the present invention has better dielectric properties, and the dielectric constant is about 4.5 at 1 MHz, which is more than 30% lower than the dielectric constant of the composite material filled with an equivalent amount of alkali-free glass fiber;

(2) The drawing temperature of the glass fiber filled in the present invention is below 1350°C, the fiber forming property is very good, it can be drawn continuously, which is beneficial to industrial production; at the same time, it has a tensile strength equivalent to that of the alkali-free glass fiber, and is easy for subsequent processing. It is suitable as a reinforcing material for printed circuit substrates and has great commercial prospects;

(3) The composite material of the present invention contains less or substantially no Li ₂ O, which can effectively reduce the cost of raw materials. At the same time, it does not contain toxic Sb ₂ O ₃ , so as to avoid affecting human health and causing pollution to the environment;

(4) The method of the present invention is simple and universal, and is suitable for industrial continuous production.

Description of drawings

Fig. 1 is the scanning electron micrograph of glass fiber in embodiment 1;

Fig. 2 is the tensile strength contrast of glass fiber and E glass fiber in embodiment 1;

Fig. 3 is the dielectric constant of epoxy resin, E glass fiber and the composite material obtained in Examples 1-4.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

The glass fiber composition of this embodiment and the weight percentage of each component include: SiO ₂ 51.3%, B ₂ O ₃ 25%, Al ₂ O ₃ 12%, CaO 5.5%, MgO 2.5%, Na ₂ O0. 15%, K ₂ O 0.15%, CaF ₂ 0.9%, TiO ₂ 2%, ZrO ₂ 0.5%. Accurately weigh 200 g of various raw materials in an agate mortar according to the formula, mix the powder evenly and put it into an alumina crucible, put it into an electric furnace for high-temperature melting, the melting temperature is 1500 ° C, and keep it for 8 hours. After the melting is completed, the molten glass is poured into cold water prepared in advance for quenching to obtain broken glass. The cullet was added to the crucible of the glass fiber monofilament test line, and the temperature of the crucible was 1340°C. The glass needs to be kept warm in the crucible for 1 hour for secondary melting. Observe the state of the molten glass through the discharge port. When the glass liquid can fall naturally from the discharge port, close the discharge port and start drawing glass fibers from the spinneret hole. Fig. 1 is a scanning electron micrograph of the glass fiber of this embodiment, with a diameter of about 10 μm. Fig. 2 is the tensile strength of the glass fiber of this embodiment, which is equivalent to the alkali-free glass fiber (E glass fiber). 1 g of the prepared glass fiber was spread in the mold, and the mass ratio of the prepared glass fiber to the epoxy resin was 4:10. Preheat it in a 50°C oven to remove surface air bubbles. The epoxy resin and the curing agent diethylenetriamine were mixed according to the mass ratio of 10:1, and stirred for 10 minutes to a slightly exothermic liquid state. After ultrasonication for 5 minutes, let it stand for 30 minutes to eliminate the bubbles generated during the stirring process, then pour it into a preheated mold with glass fiber laid flat, put it in a vacuum oven, keep it at 50°C for 0.5h, and keep it at 80°C for 2h. Insulate at 120°C for 4 hours to make it fully cured. The surface of the sample obtained in this way is flat, with few defects and almost no air bubbles. The composite material sample is in the shape of a disc with flat surfaces on both sides, with a diameter of 3 cm and a thickness of 5 mm. The STD-A non-metallic material dielectric loss and dielectric constant meter is used for testing, the method is the resonance method, and the frequency is 1MHz. As shown in FIG. 3 , the dielectric constant of the composite material of this embodiment is 4.49.

Example 2

The glass fiber composition of this embodiment and the weight percent example of each component include: _SiO2 51.3%, B2O3 ₂₂ %, _{Al2O3 15} %, _CaO5.5 %, MgO2.5%, _Na2O2 . 5%, K ₂ O 0.15%, CaF ₂ 0.9%, TiO ₂ 2%, ZrO ₂ 0.5%. Accurately weigh 200g of various raw materials in an agate mortar according to the formula, mix the powder evenly and put it into an alumina crucible, put it into an electric furnace for high-temperature melting, the melting temperature is 1500°C, and keep it warm for 8 hours. After the melting is completed, the molten glass is poured into cold water prepared in advance for quenching to obtain broken glass. The cullet was added to the crucible of the glass fiber monofilament test line, and the temperature of the crucible was 1340°C. The glass needs to be kept warm in the crucible for 1 hour for secondary melting. Observe the state of the molten glass through the discharge port. When the glass liquid can fall naturally from the discharge port, close the discharge port and start drawing glass fibers from the spinneret hole. 1 g of the prepared glass fiber was spread in the mold, and the mass ratio of the prepared glass fiber to the epoxy resin was 4:10. Preheat it in a 50°C oven to remove surface air bubbles. The epoxy resin and the curing agent diethylenetriamine were mixed according to the mass ratio of 10:1, and stirred for 10 minutes to a slightly exothermic liquid state. After ultrasonication for 5 minutes, let it stand for 30 minutes to eliminate the bubbles generated during the stirring process, then pour it into a preheated mold with glass fiber laid flat, put it in a vacuum oven, keep it at 50°C for 0.5h, and keep it at 80°C for 2h. Insulate at 120°C for 4 hours to make it fully cured. The surface of the sample obtained in this way is flat, with few defects and almost no air bubbles. The composite material sample is in the shape of a disc with flat surfaces on both sides, with a diameter of 3 cm and a thickness of 5 mm. The STD-A non-metallic material dielectric loss and dielectric constant meter is used for testing, the method is the resonance method, and the frequency is 1MHz. As shown in FIG. 3 , the dielectric constant of the composite material of this embodiment is 4.52.

Example 3

The glass fiber composition of this embodiment and the weight percentage of each component include: SiO ₂ 51.3%, B ₂ O ₃ 25%, Al ₂ O ₃ 12%, CaO 2.5%, MgO 5.5%, Na ₂ O0. 15%, K ₂ O 0.15%, CaF ₂ 0.9%, TiO ₂ 2%, ZrO ₂ 0.5%. Accurately weigh 200g of various raw materials in an agate mortar according to the formula, mix the powder evenly and put it into an alumina crucible, put it into an electric furnace for high-temperature melting, the melting temperature is 1550°C, and keep it warm for 6 hours. After the melting is completed, the molten glass is poured into cold water prepared in advance for quenching to obtain broken glass. The cullet was added to the crucible of the glass fiber monofilament test line, and the temperature of the crucible was 1350°C. The glass needs to be kept warm for 0.5h in the crucible for secondary melting. Observe the state of the molten glass through the discharge port. When the glass liquid can fall naturally from the discharge port, close the discharge port and start drawing glass fibers from the spinneret hole. 0.5 g of the prepared glass fiber was spread in the mold, and the mass ratio of the prepared glass fiber to the epoxy resin was 2:10. Preheat it in a 50°C oven to remove surface air bubbles. The epoxy resin and the curing agent diethylenetriamine were mixed according to the mass ratio of 10:1, and stirred for 10 minutes to a slightly exothermic liquid state. After ultrasonication for 5 minutes, let it stand for 30 minutes to eliminate the bubbles generated during the stirring process, then pour it into a preheated mold with glass fiber laid flat, put it in a vacuum oven, keep it at 50°C for 0.5h, and keep it at 80°C for 2h. Insulate at 120°C for 4 hours to make it fully cured. The surface of the sample obtained in this way is flat, with few defects and almost no air bubbles. The composite material sample is in the shape of a disc with flat surfaces on both sides, with a diameter of 3 cm and a thickness of 5 mm. The STD-A non-metallic material dielectric loss and dielectric constant meter is used for testing, the method is the resonance method, and the frequency is 1MHz. As shown in FIG. 3 , the dielectric constant of the composite material of this embodiment is 4.48.

Example 4

The glass fiber composition and the weight percentage of each component in this embodiment include: SiO ₂ 51%, B ₂ O ₃ 25%, Al ₂ O ₃ 12%, CaO 5.5%, MgO 2.5%, Na ₂ O0. 3%, K ₂ O 0.15%, CaF ₂ 0.9%, TiO ₂ 2%, ZrO ₂ 0.5%. Accurately weigh 200g of various raw materials in an agate mortar according to the formula, mix the powder evenly and put it into an alumina crucible, put it into an electric furnace for high-temperature melting, the melting temperature is 1550°C, and keep it warm for 6 hours. After the melting is completed, the molten glass is poured into cold water prepared in advance for quenching to obtain broken glass. The cullet was added to the crucible of the glass fiber monofilament test line, and the temperature of the crucible was 1350°C. The glass needs to be kept warm for 0.5h in the crucible for secondary melting. Observe the state of the molten glass through the discharge port. When the glass liquid can fall naturally from the discharge port, close the discharge port and start drawing glass fibers from the spinneret hole. 0.5 g of the prepared glass fiber was spread in the mold, and the mass ratio of the prepared glass fiber to the epoxy resin was 2:10. Preheat it in a 50°C oven to remove surface air bubbles. The epoxy resin and the curing agent diethylenetriamine were mixed according to the mass ratio of 10:1, and stirred for 10 minutes to a slightly exothermic liquid state. After ultrasonication for 5 minutes, let it stand for 30 minutes to eliminate the bubbles generated during the stirring process, then pour it into a preheated mold with glass fiber laid flat, put it in a vacuum oven, keep it at 50°C for 0.5h, and keep it at 80°C for 2h. Insulate at 120°C for 4 hours to make it fully cured. The surface of the sample obtained in this way is flat, with few defects and almost no air bubbles. The composite material sample is in the shape of a disc with flat surfaces on both sides, with a diameter of 3 cm and a thickness of 5 mm. The STD-A non-metallic material dielectric loss and dielectric constant meter is used for testing, the method is the resonance method, and the frequency is 1MHz. As shown in FIG. 3 , the dielectric constant of the composite material of this embodiment is 4.45.

Claims (10)

1. A glass fiber composite material with a low dielectric constant, characterized in that the composite material is composed of glass fiber filled epoxy resin; wherein the weight ratio of glass fiber to epoxy resin is 2 to 4:10. 2. A glass fiber composite material with low dielectric constant according to claim 1, characterized in that, the composition of the glass fiber comprises: SiO ₂ 51%-52%, B ₂ O ₃ 20 %~25%, _{Al2O3 10} %~15%, CaO2%~6%, MgO2%~ ₆ %, Na2O0.15%~0.3%, _K2O0 ~0.3%, _Li2O0 ~0.3% , CaF ₂ 0-0.9%, TiO ₂ 0-2%, ZrO ₂ 0-0.5%. 3 . The glass fiber composite material with low dielectric constant according to claim 2 , wherein the weight percentage of CaO and MgO satisfies: CaO+MgO=8%. 4. A glass fiber composite material with a low dielectric constant according to claim 2, characterized in that the weight percent of Na ₂ O, K ₂ O and Li ₂ O satisfies: Na ₂ O+K ₂ O+Li ₂ O=0.3%˜0.6%, wherein, Na ₂ O=K ₂ O or Na ₂ O=K ₂ O+Li ₂ O. 5. A glass fiber composite material with low dielectric constant according to claim 2, characterized in that the weight percentage of the CaF ₂ is 0.9%. 6. A glass fiber composite material with low dielectric constant according to claim 2, characterized in that the weight percentage of said TiO ₂ is 2%. 7. A glass fiber composite material with low dielectric constant according to claim ₂ , characterized in that the weight percentage of said ZrO2 is 0.5%. 8. A glass fiber composite material with low dielectric constant according to claim 1, characterized in that the spinning temperature of the glass fiber is 1340-1350°C. 9. A glass fiber composite material with low dielectric constant according to claim 1, characterized in that, when the frequency of the composite material is 1 MHz, the dielectric constant is about 4.5. 10. A method for preparing a glass fiber composite material with a low dielectric constant, comprising: (1) Weigh the components of the glass fiber, put them in a crucible after mixing, melt at 1500-1550°C for 6-8 hours, and quench to obtain cullet; add the cullet to the crucible of the glass fiber monofilament test line, 1340 Secondary melting at ~1350°C for 0.5~1h, wire drawing, to obtain glass fibers, take 0.5~1g of glass fibers and spread them in a polytetrafluoroethylene mold, put them in an oven at 50°C for preheating; (2) Get epoxy resin and curing agent and mix by mass ratio 10:1, stir, ultrasonic, leave standstill; Then join in the mold of step (1), solidify, obtain the glass fiber composite material with low dielectric constant; Wherein, the weight ratio of glass fiber to epoxy resin is 2-4:10.