JP2004351777A - Method and equipment for controlling pressure of hot-melt material, and method for producing electrical component coated for protection with thermoplastic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a pressure in a mold for lessening voids in a hot melt, in hot-melt molding. <P>SOLUTION: The pressure of the hot melt inside a gun 40 for injecting the hot melt into the mold 200 is detected by a pressure sensor 500 provided for the gun 40. Based on the detected pressure, the pressure of the hot melt to be injected into the mold 200 is controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and a device for controlling the pressure of a hot-melt material, and to a method for producing an electrical component which is protectively coated with a thermoplastic resin. In particular, the present invention relates to a method and apparatus for controlling the pressure of a hot melt material when the hot melt material is injected into a mold in hot melt molding.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is a method of sealing a circuit board on which electronic components are mounted by injection molding so as to cover almost the entire surface with a thermoplastic resin (for example, see Patent Document 1). According to this method, the resin material and the solder can be rapidly cooled and solidified before the solder of the electronic component is re-melted.
Also, in order to seal the printed circuit board on which the electronic components are mounted at a relatively low temperature and low pressure, the printed circuit board on which the electronic components are mounted is placed in a mold cavity, and a polyamide resin heated and melted at 160 to 230 ° C. 2.45 × 10 ⁵ ~ 24.5 × 10 ⁵ Pa (2.5 to 25 kg / cm ² There is a hot-melt molding method in which a mold is injected into a mold cavity within a pressure range of (1) and the printed circuit board is thereby sealed with a polyamide resin (for example, see Patent Document 2).
[0003]
[Patent Document 1]
JP-A-9-92668 (abstract)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-133665 (Claim 1)
[0004]
[Problems to be solved by the invention]
However, in the conventional hot-melt molding method, when a low-viscosity hot-melt is used, turbulence is likely to occur and voids are often generated. Therefore, every time a void is generated, it is necessary to change the design of the mold or add an air reservoir.
In hot melt molding, in general, when controlling the flow rate of hot melt during injection of hot melt into a mold, the diameter of a nozzle orifice is changed, the diameter of a mold gate, the length of a sprue or a runner is controlled. Or had to change.
If the flow rate of the hot melt is low, problems such as poor filling of the hot melt into the mold and poor adhesion between the hot melt and the circuit board occur.
Conversely, by increasing the injection pressure of the hot melt into the mold, the flow rate of the hot melt can be increased and the injection time of the hot melt can be shortened. However, when the hot melt is a low-viscosity material, turbulence occurs due to an increase in the flow rate of the hot melt. Due to this turbulence, the hot melt entrains the air, causing voids in the hot melt and causing defective products. Therefore, the injection pressure must be set so that the flow rate of the hot melt does not cause turbulence.
However, when voids cannot be prevented by changing the flow velocity, a large number of molds must be prototyped and remodeled in order to eliminate the voids (entrapment of air in the product). In addition, there was an increase in production costs due to the production of a large number of air chambers and runners.
[0005]
In a conventional hot melt molding apparatus using a gear pump, the gear pump is operated to open the valve of the gun and to inject the hot melt into the mold. At this time, the internal pressure of the gun temporarily decreases. When the filling of the mold with the hot melt is completed, the internal pressure of the gun increases, and the pressure is maintained while the valve of the gun is open. As a countermeasure against the generation of voids, there is a method of lowering the flow rate during injection and increasing the dwell time. In the pressure-holding step, cooling can be performed while replenishing a material corresponding to the decrease in the volume of the hot melt in the mold.
However, when a void occurs, it is only necessary to change the rotation speed of the gear pump or change the settings of the injection pressure and the holding pressure. For this reason, when a void is generated, it is necessary to change the design of the inflow path and the design of the mold.
[0006]
In a conventional hot melt molding device (constant volume filling method) using an air cylinder, it is necessary to change the back pressure inside the gun in order to change the flow rate of the hot melt when injecting the hot melt into the mold. . In order to change the back pressure, it is necessary to change the diameter and length of the nozzle orifice, or to change the opening area between the needle and the valve seat using a gun equipped with a needle (valve element) clearance adjusting mechanism. As described above, since the back pressure inside the gun needs to be changed, there is a problem that even if the back pressure inside the gun is detected, the pressure inside the mold at the time of hot melt injection cannot be measured.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus capable of preventing the generation of voids in any melter or mold by controlling the pressure of a hot-melt material.
Another object of the present invention is to provide a method and apparatus for detecting the pressure of a hot melt material inside a gun and controlling the pressure of the hot melt material based on the detection result.
Another object of the present invention is to provide a method and an apparatus capable of preventing generation of voids in a product by controlling a pressure after a step of injecting a hot-melt material into a mold.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention adopts the following method for controlling the pressure of a hot-melt material.
That is, the pressure of the hot melt material inside the gun is detected by a pressure sensor provided in the gun for injecting the hot melt material into the mold, and the pressure of the hot melt material injected into the mold based on the detected pressure. Control.
According to the method of the present invention, since the pressure of the hot-melt material can be controlled, the generation of voids can be prevented without changing the nozzle orifice diameter or adjusting the opening area by the needle valve. . Since the generation of voids can be prevented, the orifice diameter can be made larger than before. Therefore, by detecting the pressure inside the gun, the pressure inside the mold can be detected more accurately than the conventional one. Thereby, the pressure of the hot-melt material can be controlled more accurately based on the detection result of the pressure sensor provided on the gun.
[0009]
After injecting the hot melt material into the mold, the pressure of the hot melt material may be controlled. Thereby, the voids generated and growing in the mold can be taken out of the hot-melt material.
[0010]
Further, the method of controlling the pressure of the hot-melt material of the present invention includes a step of injecting the hot-melt material into the mold, a pressure releasing step of rapidly reducing the pressure of the hot-melt material, And increasing the pressure gradually.
Since the present invention includes the pressure releasing step and the pressure increasing step, it is possible to prevent the occurrence of voids in the product.
The method may include a detection step of detecting the pressure of the hot melt material inside the gun by a pressure sensor provided on the gun for injecting the hot melt material into the mold.
The detecting step includes a step of detecting that the pressure of the hot-melt material has become equal to or higher than a predetermined pressure during the pouring step, and after the pressure of the hot-melt material has become equal to or higher than the predetermined pressure, the pressure releasing step is performed. May be.
The pressure releasing step may include maintaining the pressure of the hot-melt material at substantially zero for a predetermined time.
In the pressure increasing step, the pressure of the hot-melt material may be increased substantially linearly with a predetermined inclination.
In the pressure increasing step, the pressure of the hot-melt material may be increased in a number of steps in a stepwise manner.
In the pressure increasing step, the pressure of the hot-melt material may be increased along a first straight line having a first slope and a second straight line having a second slope.
[0011]
An apparatus for controlling the pressure of a hot-melt material according to the present invention includes a discharge port, a valve assembly for opening and closing the discharge port, and a hot-melt material chamber communicating with the discharge port. A gun module for injecting the hot melt material; a gear pump for pumping the hot melt material from a hot melt material source to the hot melt material chamber of the gun module; and controlling a pressure of the hot melt material in the hot melt material chamber. Control system, a pressure sensor attached to the gun module for detecting pressure in the hot-melt material chamber, and a control device for controlling the pressure control system based on the pressure detected by the pressure sensor And
[0012]
The method for producing an electric component that is protectively coated with a thermoplastic resin according to the present invention includes the steps of: injecting a thermoplastic resin from a gun into a cavity of a mold in which the electric component is disposed; A pressure releasing step of rapidly reducing the pressure of the thermoplastic resin when the pressure of the thermoplastic resin becomes equal to or higher than the first pressure, and a pressure increasing step of gradually increasing the pressure of the thermoplastic resin to the second pressure. And a pressure holding step of maintaining the pressure of the thermoplastic resin at the second pressure.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments are not intended to limit the scope of the present invention thereto unless otherwise specified. Absent.
FIG. 1 is a schematic configuration diagram of a hot melt material injection apparatus 1 using a method of injecting a hot melt material into a mold according to the present invention.
[0014]
(Hot-melted material supply source)
A tank 10 serving as a hot melt material supply source stores a hot melt material 12. As the hot melt material 12, there is a thermoplastic resin such as hot melt or polyamide resin. The hot-melt material 12 in the tank 10 is pressure-fed to the gun module 40 via the filter 16 by the gear pump 14. The air valve 22 adjusts the pressure of the hot melt material 12 sent to the gun module 40. The air valve 22 includes an inlet chamber 24, an outlet chamber 26, a cylinder chamber 28, and a valve assembly 30. An opening 25 through which the hot-melt material 12 passes is provided between the inlet chamber 24 and the outlet chamber 26. The valve assembly 30 is provided in a valve chamber 30a, a valve element 30b provided at one end of the valve rod 30a to open and close the opening 25, and provided in a cylinder chamber 28 provided at the other end of the valve rod 30a. And a piston portion 30c. The air pressure in the cylinder chamber 28 is P1, the pressure of the hot melt material in the inlet chamber 24 is P2, the area of the piston 30c is A1, and the area of the opening 25 is A2. When the pressure P2 of the inlet chamber 24 rises and the condition of P2 × A2> P1 × A1 is satisfied, the valve assembly 30 moves rightward in FIG. 1 against the pressure P1 of the air by the pressure P2 of the hot-melt material. And the opening 25 is opened. Thereby, the hot-melt material flows from the inlet chamber 24 through the opening 25 to the outlet chamber 26, and is returned from the outlet chamber 26 to the tank 10 via the conduit 27.
[0015]
(Gun module)
The gun module 40 includes a main body 42 and a nozzle tip 44. The main body 42 has a hot-melt material chamber 46, a cylinder chamber 48, and a valve assembly 50. The hot melt material chamber 46 communicates with an inlet 42 a for receiving the hot melt material 12 from the tank 10 via the conduit 18. Further, the hot-melt material chamber 46 communicates with a discharge port 42b for discharging the hot-melt material. The discharge port 42b communicates with an orifice 45 provided in a nozzle tip 44 attached to the tip of the main body 42. The hot melt material 12 is injected into the mold 200 through the orifice 45. The cylinder chamber 48 communicates with an air inlet 48a for receiving air from an air supply source 70 via a solenoid valve 60. The valve assembly 50 is disposed in the cylinder chamber 48 provided at one end of the valve stem 50a, provided at one end of the valve stem 50a for opening and closing the discharge port 42b, and provided at the other end of the valve stem 50a. And a piston portion 50c. The spring 52 is disposed in the cylinder chamber 48 and engages with the piston 50c. The spring 52 urges the piston portion 50c so that the valve body 50b closes the discharge port 42b. The control device 300 controls opening and closing of the solenoid valve 60. When the solenoid valve 60 is opened, air pressurized from the air supply source 70 is supplied to the cylinder chamber 48 via the air inlet 48a. The pressurized air acts on the piston portion 50c, moves the valve assembly 50 upward in FIG. 1 against the urging force of the spring 52, and opens the discharge port 42b. When the discharge port 42b is opened, the hot-melt material is injected into the mold 200 from the hot-melt material chamber 46 through the discharge port 42b and the orifice 45.
[0016]
(Pressure control system)
The pressure P3 of the hot melt material in the hot melt material chamber 46 of the gun body 42 can be changed by controlling the pressure P1 of the air in the cylinder chamber 28 of the air valve 22. The pressure P3 of the hot melt material in the hot melt material chamber 46 is measured by a pressure sensor 500 provided in the hot melt material chamber 46. The cylinder chamber 28 of the air valve 22 is connected to a shuttle valve 80. Shuttle valve 80 has two inlets 80a and 80b. When the air pressure at the inlet 80a is higher than the air pressure at the inlet 80b, the shuttle valve 80 closes the inlet 80b and supplies the air from the inlet 80a to the cylinder chamber 28. Conversely, when the air pressure at the inlet 80b is higher than the air pressure at the inlet 80a, the inlet 80a is closed and the air from the inlet 80b is supplied to the cylinder chamber 28. One inlet 80a of the shuttle valve 80 is connected to a solenoid valve 82 for initial injection. The initial injection solenoid valve 82 is connected to the air supply source 70 via an injection pressure regulator 84. The injection pressure regulator 84 adjusts the pressure of the air from the air supply source 70 to a predetermined set pressure. The other inlet 80b of the shuttle valve 80 is connected to the electropneumatic conversion regulator 86. The electropneumatic conversion regulator 86 is connected to the air supply source 70. The electropneumatic conversion regulator 86 adjusts the air pressure according to the magnitude of the applied voltage. The control device 300 controls the initial injection electromagnetic valve 82 and the electropneumatic conversion regulator 86.
[0017]
(Mold)
In the present embodiment, the mold 200 is shown as a two-piece mold composed of the upper mold 201 and the lower mold 202, but is not particularly limited to this. An upper mold 201 and a lower mold 202 constitute a cavity 204. A circuit board 250 to be sealed is arranged in the cavity 204. The upper mold 201 is provided with a gate 206 for receiving the hot melt material from the nozzle tip 44 of the gun module 40, a sprue 208 communicating with the gate 206, and a runner 210 communicating with the sprue 208 and the cavity 204.
[0018]
(motion)
Next, the operation of the hot melt material injection device 1 will be described.
The air supply source 70 is always about 5 × 10 ⁵ ~ 8 × 10 ⁵ Air with a pressure of Pa is supplied. The injection pressure regulator 84 adjusts the pressure of the air from the air supply source 70 to the initial set pressure Pin. The initial set pressure Pin is about 1 × 10 ⁵ ~ 2 × 10 ⁵ It is set in the range of Pa.
[0019]
The gun module 40 is moved to the mold 200 by a moving mechanism (not shown), and connects the nozzle tip 44 to the gate 206 of the mold 200. As a result, the orifice 45 and the gate 206 communicate with each other. The control device 300 issues an ON signal to the initial injection electromagnetic valve 82 to open the initial injection electromagnetic valve 82. As a result, air at the initial set pressure Pin is supplied from the inlet 80 a of the shuttle valve 80 to the cylinder chamber 28 of the air valve 22. The pressure P1 of the cylinder chamber 28 is maintained at the initial set pressure Pin, and the valve body 30b of the air valve 22 closes the opening 25.
[0020]
Since the ratio of the area A1 of the piston portion 30c of the air valve 22 to the area A2 of the opening 25 is set to about 10: 1, the pressure P2 of the inlet chamber 24 is set to an initial injection pressure about 10 times the initial set pressure Pin. When the PIN is exceeded, the valve assembly 30 moves rightward in FIG. 1 and the valve 30b opens the opening 25. That is, the initial injection pressure PIN of the inlet chamber 24 for opening the opening 25 is about 10 × 10 ⁵ ~ 20 × 10 ⁵ It is set in the range of Pa.
[0021]
When the gear pump 14 starts driving in response to a signal from the control device 300, the hot melt material 12 in the tank 10 is pumped to the gun module 40 via the filter 16 and the conduit 18. When the valve body 50b of the gun module 40 closes the discharge port 42b, the hot-melt material is not discharged out of the orifice 45 of the gun module 40. Accordingly, the hot-melt material is pumped through the filter 16 and the conduit 17 to the inlet chamber 24 of the air valve 22 to increase the pressure P2 in the inlet chamber 24. When the pressure P2 in the inlet chamber 24 exceeds the initial injection pressure PIN, the opening 25 opens. The hot-melt material flows from the inlet chamber 24 through the opening 25 to the outlet chamber 26, and is returned from the outlet chamber 26 to the tank 10 via the conduit 27. At this time, the pressure P3 of the conduit 18 and the hot-melt material chamber 46 of the gun module 40 communicating with the conduit 18 is also maintained at the initial injection pressure PIN.
[0022]
FIG. 2 is a diagram showing the relationship among the opening and closing of the gun module 40, the discharge flow rate of the hot melt material, the pressure in the cylinder chamber 28 of the air valve 22, and the pressure in the hot melt material chamber 46 of the gun module 40. Control device 300 outputs an ON signal to solenoid valve 60. Thereby, the air pressure from the air supply source 70 is applied to the cylinder chamber 48 of the gun module 40, and the valve assembly 50 is moved upward in FIG. 1 against the urging force of the spring 52, and the discharge port 42b is closed. open. When the discharge port 42b is opened, the hot-melt material is injected into the mold 200 from the hot-melt material chamber 46 through the discharge port 42b and the orifice 45. The hot melt material is injected at an initial injection pressure PIN. However, as shown in FIG. 2, when the discharge port 42b is opened, the pressure in the hot-melt material chamber 46 temporarily decreases, and gradually recovers. The pressure fluctuation during the filling period may take various patterns depending on conditions, but has no direct relation to the pressure control of the present invention. By increasing the initial injection pressure PIN, or by increasing the diameter of the orifice 45, the injection time of the hot-melt material can be shortened. However, when the hot-melt material is a low-viscosity material, turbulence occurs due to an increase in the flow rate of the hot-melt material. This turbulence causes the hot melt material to entrain air and create voids in the hot melt material. In the related art, the void causes a product defect. Therefore, in the prior art, the initial injection pressure PIN or the diameter of the orifice 45 must be set so that the flow rate of the hot-melt material does not cause turbulence. However, since the void can be removed by the pressure control method of the hot-melt material according to the present invention, the initial injection pressure PIN can be increased or the diameter of the orifice 45 can be increased according to the present invention. can do.
[0023]
Due to the opening of the discharge port 42b, the pressure P3 in the hot-melt material chamber 46 of the gun module 40 once drops significantly. Then, as the hot melt material is filled into the cavity 204 of the mold 200, the pressure P3 in the hot melt material chamber 46 increases. The pressure P3 in the hot-melt material chamber 46 corresponds to the pressure in the cavity 204. In the present embodiment, the diameter of the orifice 45 can be made larger than before, so that the pressure P3 in the hot-melt material chamber 46 can be considered to be substantially the same as the pressure in the cavity 204. The pressure P3 of the hot melt material in the hot melt material chamber 46 is measured by a pressure sensor 500 provided in the hot melt material chamber 46.
[0024]
When the cavity 204 is almost filled with the hot melt material, the pressure P3 in the hot melt material chamber 46 reaches the primary set pressure Pf. The primary set pressure Pf is set to substantially the same pressure as the initial injection pressure PIN. However, the primary set pressure Pf may be set lower or higher than the initial injection pressure PIN. When the pressure sensor 500 detects the primary set pressure Pf, the control device 300 closes the initial injection electromagnetic valve 82 and opens the cylinder chamber 28 of the air valve 22 to the atmosphere. Thereby, the pressure P1 of the cylinder chamber 28 becomes substantially zero (atmospheric pressure). Therefore, the valve 30 b of the air cylinder 22 opens the opening 25 by the pressure of the hot-melt material pumped from the gear pump 14, and the hot-melt material is returned to the tank 10. Therefore, the pressure P3 in the hot-melt material chamber 46 of the gun module 40 is also reduced to a pressure close to substantially zero (atmospheric pressure).
[0025]
When the pressure sensor 500 detects the primary set pressure Pf, the timer 310 of the control device 300 starts measuring a predetermined time T1. The predetermined time T1 is a period in which the pressure P3 in the hot-melt material chamber 46 is released to almost zero (atmospheric pressure), that is, a period in which the pressure in the cavity of the mold 200 is released. In the present embodiment, the predetermined time T1 is set in a range from about 0.5 seconds to 1.0 seconds. However, this predetermined time T1 should not be construed as being limited to the above numerical range, but is appropriately set according to the size of the mold, the shape of the mold, the hot-melt material, and the like.
[0026]
When the timer 310 finishes measuring the predetermined time T1, the sequencer 320 of the control device 300 starts controlling the electropneumatic conversion regulator 86. The sequencer 320 gradually increases the pressure P1 of the cylinder chamber 28 of the air valve 22 by gradually increasing the voltage applied to the electropneumatic conversion regulator 86. As a result, the pressure P3 of the hot melt material chamber 46 of the gun module 40 gradually increases, and the pressure of the hot melt material in the mold 200 gradually increases. The electropneumatic conversion regulator 86 increases the pressure from substantially zero pressure to the secondary set pressure Pho over a predetermined time T2. In the present embodiment, the predetermined time T2 is set in the range of 1 to 2 seconds, and the secondary set pressure Pho is about 2 × 10 ⁵ Pa is set. The predetermined time T2 and the secondary set pressure Pho are appropriately selected depending on the size, shape, and hot-melt material of the mold, and should not be construed as being limited to the above values. As the pressure P1 in the cylinder chamber rises, the pressure P3 in the hot-melt material chamber of the gun module 40 rises. In the present embodiment, as shown in FIG. 2, the pressure is increased along a straight line having a predetermined inclination. When the pressure P1 in the cylinder chamber reaches Pho, the pressure P3 in the hot-melt material chamber reaches the holding pressure PHO. The holding pressure PHO may be higher or lower than the initial injection pressure PIN, but the holding pressure PHO can be set to substantially the same pressure as the initial injection pressure PIN. However, it is considered that the case where the holding pressure PHO is larger than the initial injection pressure PIN improves the adhesion between the heat-fusible material and the substrate, and is effective in preventing sinking when the heat-fusible material is cured.
[0027]
The electropneumatic conversion regulator 86 holds the pressure P1 in the cylinder chamber at Pho for a predetermined time T3. The predetermined period T3 is set to about 5 to 10 seconds, but is not particularly limited to this range. This predetermined period T3 is generally called a dwell period. During the dwelling period, the hot-melt material is replenished so as to compensate for the cooling shrinkage after filling, and the molding accuracy can be improved. It is also possible that the hot-melt material cools and hardens during this dwell period.
[0028]
Control device 300 outputs an OFF signal to solenoid valve 60. As a result, the air pressure from the air supply source 70 is shut off, the pressure in the cylinder chamber 48 of the gun module 40 decreases, and the urging force of the spring 52 moves the valve assembly 50 downward in FIG. The discharge port 42b is closed. After that, the control device 300 stops applying the voltage to the electropneumatic conversion regulator 86. The gun module 40 is separated from the mold 200 by a moving mechanism (not shown). Then, the upper mold 201 is opened, and the circuit board sealed (coated) with the hot-melt material is taken out. When working continuously, the circuit board to be sealed next is placed in the lower mold 202, and after closing the upper mold 201, the gun module 40 is connected to the mold 200, and Repeat the operation. When a different product is sealed, a new mold is sent, the gun module 40 is connected to the mold 200, and the above operation is repeated.
[0029]
By the way, during the filling period of the hot-melt material, it is considered that the air entrained in the hot-melt material grows as bubbles and forms voids. When the pressure sensor 500 detects the primary set pressure Pf, the pressure inside the mold is suddenly reduced, so that it is considered that air bubbles go out of the hot-melt material. Then, it is considered that the bubbles are pushed out of the mold through the mating surfaces of the mold by gradually increasing the pressure in the mold.
[0030]
(Pressure rise pattern)
The pressure rising pattern of the hot-melt material during the pressure rising period is not limited to the linear pattern shown in FIG. 2, but may be, for example, as shown in FIG. The pressure may be gradually increased gradually.
Also, as shown in FIG. 4, the pressure rise period is divided into two, the pressure rise rate is reduced so that voids are released from the hot-melt material in the first period T2a, and when the voids are released, In the second period T2b, the pressure increase rate may be increased. The pressure rise period may be divided into three or more periods.
Other pressure increase patterns may be used as long as the present invention can be achieved by gradually increasing the pressure. It is important to gradually increase the pressure.
[0031]
(Another pressure control system)
Another pressure control system is shown in FIG. In the hot melt material injection apparatus shown in FIG. 1, a solenoid valve 82 for initial injection, an injection pressure regulator 84, and an electropneumatic conversion regulator 86 are used to control the pressure. However, the method for injecting the hot-melt material into the mold according to the present invention can be implemented in another pressure control system as shown in FIG. That is, the air valve 22 is controlled by one electropneumatic conversion regulator 186.
5, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description will be omitted. That is, the control device 300 controls the voltage applied to the electropneumatic conversion regulator 186 to control the air pressure supplied to the air valve. This controls the pressure of the hot-melt material.
[0032]
INDUSTRIAL APPLICABILITY The present invention can be suitably used not only for sealing (coating) electronic circuit boards, but also for sealing or filling electric and electronic components such as wire harnesses, waterproof connectors, collective connectors, and various sensors. In addition, since the present invention is sealing by low pressure, it is possible to minimize damage to electric components and electronic components of a circuit board.
[0033]
【The invention's effect】
As is apparent from the above description, according to the present invention, the pressure of the hot-melt material can be controlled, which is particularly useful.
According to the method of the present invention, since the pressure of the hot-melt material can be controlled, the opening area of the needle and the valve seat can be reduced by changing the orifice diameter of the nozzle or using a gun equipped with a needle (valve) gap adjusting mechanism. Even without adjustment, the generation of voids can be prevented. Since the generation of voids can be prevented, the orifice diameter can be made larger than before. Therefore, by detecting the pressure inside the gun, the pressure inside the mold can be detected more accurately than the conventional one. Thereby, the pressure of the hot-melt material can be controlled more accurately based on the detection result of the pressure sensor provided on the gun.
[0034]
In the prior art, when the orifice diameter of the nozzle is increased and the hot-melt material is injected into the mold at the conventionally required initial injection pressure, the flow rate of the hot-melt material increases, and turbulence occurs. Due to this turbulence, many voids were generated in the hot-melt material filled in the mold. Therefore, the orifice diameter of the nozzle was reduced so that the flow rate did not increase. When the diameter of the orifice is reduced, the back pressure of the hot melt material in the hot melt material chamber of the gun body increases, and the pressure difference between the pressure in the hot melt material chamber and the pressure in the mold cavity increases. Therefore, even when the pressure in the hot-melt material chamber is detected by the pressure sensor, the pressure in the cavity cannot be accurately detected due to such a large pressure difference.
[0035]
According to the present invention, since the generation of voids can be prevented, the orifice diameter of the nozzle can be increased. Therefore, the pressure difference between the pressure in the hot-melt material chamber and the pressure in the cavity of the mold can be reduced. Therefore, there is an effect that the pressure in the cavity can be more accurately detected by detecting the pressure in the hot-melt material chamber by the pressure sensor. Further, since the diameter of the orifice can be increased, the frequency of occurrence of nozzle clogging can be reduced.
[0036]
The present invention is particularly effective for hot-melt materials having a low viscosity when heated, such as polyamide resins.
[0037]
The present invention is not limited to the above embodiments, and can be embodied in other various forms without departing from the characteristics thereof. Therefore, the above-described embodiment is merely an example in every aspect, and should not be interpreted in a limited manner. The scope of the present invention is defined by the appended claims, and is not limited by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hot melt material injection apparatus 1 using a method of injecting a hot melt material into a mold according to the present invention.
FIG. 2 is a diagram showing a relationship among an opening / closing timing of a gun module 40, a discharge flow rate of a hot melt material, a pressure in a cylinder chamber 28 of an air valve 22, and a pressure in a hot melt material chamber 46 of the gun module 40.
FIG. 3 is a diagram showing a pressure increase pattern in which the pressure of a hot-melt material is gradually increased gradually and gradually many times.
FIG. 4 is a diagram showing a pressure pattern in which the pressure of a hot-melt material is gradually increased in accordance with two pressure rising straight lines having different slopes.
FIG. 5 is a schematic configuration diagram of a hot-melt material injection apparatus according to another embodiment of the present invention.
[Explanation of symbols]
10 tanks
14 Gear pump
40 Gun Module
42b outlet
46 Heat melting material room
50 Valve assembly
200 mold
300 control device
500 pressure sensor

Claims (11)

The pressure of the hot melt material inside the gun is detected by the pressure sensor provided in the gun for injecting the hot melt material into the mold,
A method for controlling the pressure of a hot-melt material, wherein the pressure of the hot-melt material injected into a mold is controlled based on the detected pressure. The method according to claim 1, wherein the pressure of the hot melt material is controlled after injecting the hot melt material into the mold. An injection step of injecting the hot melt material into the mold,
A pressure release step for rapidly reducing the pressure of the hot melt material,
A pressure increasing step of gradually increasing the pressure of the hot-melt material. The method according to claim 3, further comprising a detecting step of detecting a pressure of the hot melt material inside the gun by a pressure sensor provided on the gun for injecting the hot melt material into the mold. The detecting step includes a step of detecting that the pressure of the hot-melt material has become equal to or higher than a predetermined pressure during the pouring step,
The method according to claim 4, wherein the pressure releasing step is performed after the pressure of the hot-melt material becomes equal to or higher than a predetermined pressure. The method of any of claims 3 to 5, wherein the step of relieving comprises maintaining the pressure of the hot melt material at substantially zero for a predetermined time. 7. The method according to claim 3, wherein the pressure increasing step increases the pressure of the hot-melt material in a substantially linear manner with a predetermined slope. 7. The method according to claim 3, wherein the step of increasing the pressure increases the pressure of the hot-melt material in multiple steps in a stepwise manner. 7. The pressure increasing step according to claim 3, wherein the pressure of the hot-melt material is increased along a first straight line having a first slope and a second straight line having a second slope. the method of. A discharge port, a valve assembly for opening and closing the discharge port, and a hot melt material chamber communicating with the discharge port, a gun module for injecting the hot melt material into the mold,
A gear pump for pumping hot melt material from a hot melt material source to the hot melt material chamber of the gun module;
A pressure control system for controlling the pressure of the hot melt material in the hot melt material chamber,
A pressure sensor attached to the gun module to detect pressure in the hot melt material chamber;
A controller for controlling the pressure control system based on the pressure detected by the pressure sensor. A method for producing an electrical component that is protectively coated with a thermoplastic resin,
An injection step of injecting a thermoplastic resin from a gun into a mold cavity in which electric components are arranged,
When the pressure of the thermoplastic resin in the gun is equal to or higher than the first pressure in the injection step, a pressure release step of rapidly reducing the pressure of the thermoplastic resin,
A pressure increasing step of gradually increasing the pressure of the thermoplastic resin to the second pressure,
Holding the pressure of the thermoplastic resin at the second pressure.

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