CN113385763B - Vacuum reflow soldering positive and negative pressure combined soldering process - Google Patents
Vacuum reflow soldering positive and negative pressure combined soldering process Download PDFInfo
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- CN113385763B CN113385763B CN202110792900.4A CN202110792900A CN113385763B CN 113385763 B CN113385763 B CN 113385763B CN 202110792900 A CN202110792900 A CN 202110792900A CN 113385763 B CN113385763 B CN 113385763B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
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Abstract
The invention discloses a positive and negative pressure combined welding process for vacuum reflow soldering, which relates to the technical field of vacuum reflow soldering and comprises the following steps: debugging vacuum chamber equipment; vacuumizing at normal temperature until the pressure in the vacuum chamber is less than or equal to a preset pressure value of negative pressure of 0.05-100 PA; filling a reducing agent into the vacuum chamber at normal temperature until the positive pressure is 1000-500000 PA; heating to 160-180 ℃; then heating to the melting point of the solder of 217 ℃; heating to 245-260 ℃ and keeping the temperature for 1-30 seconds; vacuumizing for 20-30 seconds, and maintaining the vacuum degree in the vacuum chamber at a negative pressure of 0.01-100 PA; cooling; the internal pressure of the vacuum chamber reaches the normal pressure; when the preset cooling temperature is reached, the weldment is taken out, bubbles in the solder are removed under the action of positive pressure, then the bubbles in the solder are removed again when the solder is vacuumized to negative pressure, and the discharge time of the bubbles is greatly prolonged by a positive-negative pressure combination mode, so that the voidage of the solder is far lower than that of the traditional process.
Description
Technical Field
The invention relates to the technical field of vacuum reflow soldering, in particular to a positive and negative pressure combined soldering process for vacuum reflow soldering.
Background
A vacuum reflow soldering process is a reflow soldering technology which introduces a vacuum environment in the reflow soldering process, compared with the traditional reflow soldering, the vacuum reflow soldering is performed on the rear section of a product entering a reflow region, a vacuum environment is manufactured, the atmospheric pressure can be reduced to below 500Pa and is kept for a period of time, so that the combination of vacuum and reflow soldering is realized, at the moment, a solder joint is still in a molten state, the external environment of the solder joint is close to vacuum, bubbles in the solder joint can overflow from the solder joint due to the effect of the pressure difference between the inside and the outside of the solder joint, the voidage of the solder joint can be reduced, the low voidage is particularly important for power devices with large-area solder pads, and as high-power devices need to transmit current and heat energy through the large-area solder pads, the voidage in the solder joint is reduced, and the electric conduction and heat conduction performance of the devices can be fundamentally improved.
The existing vacuum reflow soldering process flow is as follows: vacuumizing, filling nitrogen to a negative pressure of 50000 PA-100000 PA, heating to 160-180 ℃ at a constant temperature, then raising the temperature to a melting point of 217 ℃, heating to 245-260 ℃, keeping the temperature for 0-10 seconds, vacuumizing, keeping the temperature for 0-100 seconds, cooling to 200 ℃ -normal temperature, filling nitrogen to normal pressure, and taking a part, wherein the process has the following defects in practical application: bubbles in the solder cannot be automatically broken under the condition of negative pressure, and finally the void ratio is larger, the melting temperature of the solder is increased under the condition of negative pressure, and the bubble discharge time is longer, so that the vacuum-pumping time can only be prolonged in order to ensure the void ratio as far as possible, the temperature resistance time of a solder process and a device is strictly required, and if the void ratio is overlong, welding defects can be generated, and welding parts can be damaged.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a vacuum reflow soldering positive and negative pressure combined welding process, so that the voidage can be reduced and the quality of a weldment can be improved under the condition of keeping the vacuumizing time unchanged.
In order to solve the technical problems, the invention adopts the following technical scheme:
a positive and negative pressure combined welding process for vacuum reflow soldering comprises the following steps:
step S1: debugging equipment of a vacuum chamber;
step S2: the method comprises the following steps that a PLC (programmable logic controller) controls a vacuum baffle valve to be opened, vacuumizing is started at a normal temperature, the vacuumizing time is 10-120 seconds, and when the PLC detects that the pressure in a vacuum cabin is less than or equal to a preset pressure value of negative pressure 0.05-100 PA through a pressure sensor, the vacuum baffle valve is closed;
step S3: opening a reducing agent valve by a PLC (programmable logic controller), filling a reducing agent into the vacuum chamber to a positive pressure of 1000-500000 PA (Power Amplifier) under a normal temperature state, and closing the reducing agent valve when the PLC detects that the positive pressure value in the vacuum chamber reaches 1000-500000 PA through a pressure sensor;
step S4: heating to 160-180 ℃;
step S5: then heating to the melting point of the solder of 217 ℃, wherein the heating time is 60-120 seconds;
step S6: heating to 245-260 ℃ and keeping the temperature for 1-30 seconds;
step S7: then, a vacuum baffle valve is opened through a PLC controller, vacuumizing is carried out for 20-30 seconds, and the vacuum degree in a vacuum chamber is maintained at negative pressure of 0.01-100 PA;
step S8: cooling;
step S9: the internal pressure of the vacuum chamber reaches the normal pressure;
step S10: and when the detection result shows that the preset cooling temperature is reached, closing the cooling system to stop cooling, pressing a cabin opening button, opening an upper cover or a cabin door of the vacuum cabin, and taking out the weldment.
Preferably, the first and second electrodes are formed of a metal,in step S3, the reducing agent is N 2 Formic acid, H 2 CO or N 2 +H 2 Any one of the mixed gases.
Preferably, when the reducing agent is H 2 CO or N 2 +H 2 In the case of any one of the mixed gases, the following steps are further included between step S2 and step S3:
step a: the PLC controls the nitrogen filling valve to be opened, nitrogen is filled into the vacuum chamber at normal temperature, and when the PLC detects that the pressure in the vacuum chamber reaches a normal pressure value through the pressure sensor, the nitrogen filling valve is closed;
step b: the method comprises the steps that a PLC (programmable logic controller) controls a vacuum baffle valve to be opened, vacuumizing is started at a normal temperature, the vacuumizing time is set to be 10-120 seconds, and when the PLC detects that the pressure in a vacuum cabin is less than or equal to a preset pressure value of negative pressure of 0.05-100 PA through a pressure sensor, the vacuum baffle valve is closed;
step c: and (c) repeating the step a and the step b, and converting the oxygen molecules in the vacuum cabin out of the cabin until the process requirement of the weldment on the oxygen molecule content is met.
Preferably, when the reducing agent is H 2 CO or N 2 +H 2 In the case of any one of the mixed gases, the following steps are further included between step S6 and step S7:
step A: and starting the gas combustion device through the PLC at the constant temperature of 245-260 ℃ to combust and discharge the generated reductive combustible gas.
Preferably, the gas combustion device comprises a cooling cylinder, the cooling cylinder is used for connecting a gas pipeline, the top of the cooling cylinder is connected with a burner, the top of the cooling cylinder is connected with a plurality of supporting columns which are arranged around the burner, the top of each supporting column is provided with a housing, the housing is of a hollow structure, the top of the burner is located in the housing, a pulse igniter close to the top of the burner is arranged on the housing, the side wall of the cooling cylinder is provided with a lifting cylinder, the top of the lifting cylinder is provided with an igniter and a temperature sensor, one end of the igniter is close to the ignition end of the top of the burner and the pulse igniter, one end of the temperature sensor is close to the top of the burner, a movable port is formed in the side wall of the housing, the igniter penetrates through the movable port and can move up and down in the movable port, the top of the housing is provided with a combustion chamber, and the top of the combustion chamber is provided with an exhaust fan.
Preferably, the step a specifically includes:
step A1: the PLC controller controls the lifting cylinder to enable the igniter to descend, the pulse igniter is used for igniting the igniter, and when the PLC controller detects that the igniter burns normally through the temperature sensor, the PLC controller controls the lifting cylinder to enable the igniter to ascend to the position above the combustion nozzle;
step A2: discharging air of the gas pipeline to the outside of the burner;
step A3: the PLC controller controls a baffle valve of the gas combustion device to be opened;
step A4: the PLC controls a nitrogen valve to be opened, and nitrogen is filled from the bottom of the vacuum chamber;
step A5: and when the nitrogen gas filling amount is detected to be larger than or equal to the volume in the vacuum cabin, closing the gas combustion device.
Preferably, the heating ramp rate is 1.5 to 3 ℃/sec in step S4, and the heating ramp rate is 1 to 3 ℃/sec in step S6.
Preferably, step S8 is specifically:
and under the condition that the vacuum degree is maintained at the negative pressure of 0.01-100 PA, closing the heating system, opening the cooling system, and cooling the welding piece and the heating platform.
Preferably, the step S9 specifically includes:
step S91: when the temperature is cooled to 100-200 ℃, closing the vacuum baffle valve, and opening a nitrogen valve to fill nitrogen into the vacuum chamber;
step S92: and when the PLC detects that the pressure in the vacuum chamber reaches the normal pressure through the pressure sensor, the nitrogen valve is closed.
Preferably, the step S1 specifically includes:
step S11: firstly, writing the program of the whole welding process on an upper computer;
step S12: sending the welding process compiled on the upper computer to a PLC (programmable logic controller);
step S13: pressing down a cabin opening button to open an upper cover or a cabin door of the vacuum cabin;
step S14: placing a workpiece to be welded or a tool with the workpiece to be welded on a heating platform;
step S15: after an upper cover or a cabin door of the vacuum cabin is closed, a cabin closing button is pressed, and the upper cover or the cabin door locking cylinder locks the upper cover or the cabin door of the vacuum cabin;
step S16: and pressing a start button to automatically run the program.
The invention has the beneficial effects that:
1. before heating, a reducing agent is filled into a vacuum chamber to a positive pressure of 1000-500000 PA, the melting point of solder is lower than that of the solder under the normal pressure, when the temperature reaches 217 ℃ of the melting point of the solder, the solder is already in a molten state, so that bubbles in the solder are removed under the action of the positive pressure, a certain discharge time is increased in the process of heating to the melting point of 217 ℃ for 60-120 seconds, then the solder can be directly vacuumized to a negative pressure of 0.01-100 PA when the temperature is increased to 245-260 ℃, the bubbles in material welding are removed again in the process, the bubble discharge time is greatly increased in a positive-negative pressure combination mode, and under the condition of keeping the vacuum-pumping time unchanged, the void ratio of the solder is far lower than that of the traditional process, so that the quality of a welded part is improved.
2. When the reducing agent is H 2 CO or N 2 +H 2 When any one of the mixed gases is used, the reducing gas needs to be combusted, so that a special gas combustion device is configured, and in the process of discharging, combusting and reducing the combustible gas, the deflagration, explosion and the like caused by air backflow can be avoided, and the welding quality, the production safety and the personal safety are protected.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a schematic diagram of a process curve of a vacuum reflow soldering positive and negative pressure combined soldering process (N is a reducing agent) 2 Or formic acid);
FIG. 2 is a schematic diagram of a process curve of a vacuum reflow soldering positive and negative pressure combined soldering process (the reducing agent is H) 2 Or CO or N 2 +H 2 Mixed gas);
FIG. 3 is a schematic view of a vacuum chamber apparatus useful in the present invention;
FIG. 4 is a schematic structural view of a gas combustion device in the vacuum chamber apparatus;
FIG. 5 is a schematic view showing the internal structure of the gas combustion apparatus of the present invention;
FIG. 6 is a schematic view of the top view of FIG. 5;
FIG. 7 is a diagram of X-RAY detection results of weldment shots obtained by using a conventional welding process;
FIG. 8 is a diagram of X-RAY detection results of weldment punching obtained by the process of the present invention.
Reference numerals:
110-vacuum chamber, 120-gas pipeline, 130-cooling cylinder, 140-combustion nozzle, 150-housing, 151-movable port, 160-pulse igniter, 170-lifting cylinder, 180-igniter, 190-temperature sensor, 210-combustion chamber, 220-exhaust fan, 230-vacuum flapper valve, 240-locking cylinder.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the embodiments of the present invention, it should be noted that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or the orientations or positional relationships that the products of the present invention are usually placed in when used, the orientations or positional relationships are only used for convenience of describing the present invention and simplifying the description, but the terms do not indicate or imply that the devices or elements indicated must have specific orientations, be constructed in specific orientations, and operate, and therefore, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
Furthermore, the terms "horizontal", "vertical", "overhang" and the like do not require that the components be absolutely horizontal or overhang, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the embodiments of the present invention, it should be further noted that unless otherwise explicitly stated or limited, the terms "disposed," "mounted," "connected," and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Examples
As shown in fig. 1 to 6, the present embodiment provides a vacuum reflow positive and negative pressure bonding process, which includes the following steps:
step S1: preparing for equipment debugging of the vacuum chamber 110;
step S2: the PLC controls the vacuum flapper valve 230 to be opened, vacuumizing is started at normal temperature, the vacuumizing time is 10-120 seconds, and when the PLC detects that the pressure in the vacuum cabin 110 is less than or equal to a preset pressure value of negative pressure 0.05-100 PA through the pressure sensor, the vacuum flapper valve 230 is closed;
step S3: opening a reducing agent valve by a PLC (programmable logic controller), filling a reducing agent into the vacuum cabin 110 to a positive pressure of 1000-500000 PA (Power Amplifier) in a normal temperature state, and closing the reducing agent valve when the PLC detects that the positive pressure value of 1000-500000 PA in the vacuum cabin 110 is reached through a pressure sensor;
step S4: heating to 160-180 ℃;
step S5: then heating to the melting point of the solder of 217 ℃ for 60-120 seconds;
step S6: heating to 245-260 ℃ and keeping the temperature for 1-30 seconds;
step S7: then, the vacuum flapper valve 230 is opened through a PLC controller, vacuum pumping is carried out for 20-30 seconds, and the vacuum degree in the vacuum cabin 110 is maintained at the negative pressure of 0.01-100 PA;
step S8: cooling;
step S9: the pressure inside the vacuum chamber 110 reaches the normal pressure;
step S10: and when the preset cooling temperature is detected, closing the cooling system to stop cooling, pressing a cabin opening button, opening the upper cover or the cabin door of the vacuum cabin 110, and taking out the weldment.
In the process, a reducing agent is filled into a vacuum chamber 110 to a positive pressure of 1000-500000 PA before heating, the melting point of the solder is lower than that of the solder under normal pressure (namely one atmospheric pressure of 100000PA), when the temperature reaches the melting point of the solder 217 ℃, the solder is already in a molten state, so that bubbles in the solder are already removed under the action of the positive pressure, certain discharge time is added in the process of heating to the melting point of 217 ℃ (60-120 seconds), then when the temperature is increased to 245-260 ℃, the solder can be directly vacuumized to a negative pressure of 0.01-100 PA, in the process, a welding device or a workpiece can be fully heated, the solder is in the molten state, the bubbles are automatically broken under a high-pressure environment, the bubbles in material welding are discharged again, the bubble discharge time is greatly increased in a positive-negative pressure combination mode, and tests show that the removal of the bubbles in the process is 60-130 seconds longer than that in the conventional vacuum reflow welding process, the method can remove the bubbles completely, so that the voidage of the solder is far lower than that of the traditional process under the condition of keeping the vacuumizing time unchanged, thereby improving the quality of the weldment.
Specifically, in step S3, the reducing agent is N 2 Formic acid, H 2 CO or N 2 +H 2 Any of the mixed gases has a good reducibility.
In addition, when the reducing agent is N 2 Or formic acid, charging reducing agent to a positive pressure of 1000-500000 PA, and when the reducing agent is H 2 CO or N 2 +H 2 When any one of the mixed gases is used, the reducing agent is charged to a positive pressure range of 1000 to 300000 PA.
Specifically, when the reducing agent is H 2 CO or N 2 +H 2 In the case of any one of the mixed gases, the following steps are further included between step S2 and step S3:
step a: the PLC controls the nitrogen filling valve to be opened, nitrogen is filled into the vacuum chamber 110 at normal temperature, and when the PLC detects that the pressure in the vacuum chamber 110 reaches a normal pressure value through the pressure sensor, the nitrogen filling valve is closed;
step b: the PLC controls the vacuum flapper valve 230 to be opened, vacuumizing is started at normal temperature, the vacuumizing time is set to be 10-120 seconds, and when the PLC detects that the pressure in the vacuum cabin 110 is less than or equal to a preset pressure value of negative pressure 0.05-100 PA through the pressure sensor, the vacuum flapper valve 230 is closed;
step c: and repeating the step a and the step b, and converting the oxygen molecules in the vacuum chamber 110 out of the chamber until the process requirement of the weldment on the oxygen molecule content is met.
Steps a to c are mainly directed to reducing agent H 2 CO or N 2 +H 2 When any gas is mixed, the welding device has special requirements on the oxygen molecule content, so that the oxygen molecules in the vacuum chamber can be further transferred out of the chamber, the normal operation of the subsequent reduction reaction is ensured, and the corresponding relation curve chart is shown in figure 1.
It should be noted that, if the reducing agent is N 2 Or formic acid, the steps a to c may be omitted, and the corresponding relationship graph is shown in FIG. 2.
Specifically, when the reducing agent is H 2 CO or N 2 +H 2 In the case of any one of the mixed gases, the following steps are further included between step S6 and step S7:
step A: and starting the gas combustion device through the PLC at the constant temperature of 245-260 ℃ to combust and discharge the generated reductive combustible gas.
When the reducing agent is H 2 Or CO or N 2 +H 2 In the case of the mixed gas, the reduced combustible gas generated in the subsequent step needs to be burned, and therefore, a gas combustion apparatus needs to be provided.
Specifically, the gas combustion device includes a cooling cylinder 130, the cooling cylinder 130 is used for connecting a gas pipeline 120, a burner 140 is connected to the top of the cooling cylinder 130, a plurality of support columns arranged around the burner 140 are connected to the top of the cooling cylinder 130, a cover 150 is arranged on the top of each support column, the cover 150 is of a hollow structure, the top of the burner 140 is located in the cover 150, a pulse igniter 160 close to the top of the burner 140 is arranged on the cover 150, a lifting cylinder 170 is arranged on the side wall of the cooling cylinder 130, a pilot burner 180 and a temperature sensor 190 are arranged on the top of the lifting cylinder 170, one end of the pilot burner 180 is close to the top of the burner 140 and the ignition end of the pulse igniter 160, one end of the temperature sensor 190 is close to the top of the burner 140, a movable port 151 is arranged on the side wall of the cover 150, the pilot burner 180 penetrates through the movable port 151 and can move up and down in the movable port 151, a combustion chamber 210 is arranged on the top of the cover 150, the top of the combustion chamber 210 is provided with an exhaust fan 220.
When the device is used, the igniter 180 is ignited by the pulse igniter 160 to be in a normal combustion state, the igniter 180 is made to rise above the burner tip 140, at this time, the vacuum flapper valve 230 is opened, and meanwhile, nitrogen is filled into the vacuum chamber 110 through the nitrogen filling port (the bottom of the vacuum chamber 110), so that the pressure inside the vacuum chamber 110 is always greater than the normal pressure in the combustion chamber 210, air is prevented from flowing back into the vacuum chamber 110 to cause secondary oxidation damage of welding devices, and the risk of explosion due to deflagration is prevented. Meanwhile, when the discharge concentration of the reducing combustible gas in the vacuum chamber 110 is lower than the combustible concentration, and the combustible gas passes through open fire, the combustible gas can be fully combusted, the internal pressure of the burner tip 140 is higher than the external pressure of the burner tip 140, so that the combustion can be completed only outside the burner tip 140, and the outer flame of the combustion can be performed above the burner tip 140 due to the pressure, so that the aging of the burner tip 140 is reduced.
Specifically, the step a specifically includes:
step A1: the PLC controller controls the lifting cylinder 170 to enable the igniter 180 to descend, the pulse igniter 160 is used for igniting the igniter 180, and when the PLC controller detects that the igniter 180 burns normally through the temperature sensor 190, the PLC controller controls the lifting cylinder 170 to enable the igniter 180 to ascend to the upper portion of the combustion nozzle 140;
step A2: discharging the air of the gas line 120 to the outside of the burner tip 140;
step A3: the PLC controller controls a baffle valve of the gas combustion device to be opened;
step A4: the PLC controller controls a nitrogen valve to be opened, and nitrogen is filled from the bottom of the vacuum chamber 110 to the inside;
step A5: and when the nitrogen gas filling amount is detected to be larger than or equal to the volume in the vacuum chamber 110, closing the gas combustion device.
The gas combustion device specially made based on the invention can avoid deflagration, explosion and the like caused by air backflow in the process of discharging, burning and reducing combustible gas, and protect welding quality, production safety and personal safety.
Specifically, in step S4, the temperature rising slope during heating is 1.5-3 ℃/S, and in step S6, the temperature rising slope during heating is 1-3 ℃/S, so that the temperature rising speed is ensured, and the process conditions are met.
Specifically, the step S8 specifically includes:
and under the condition that the vacuum degree is maintained at the negative pressure of 0.01-100 PA, closing the heating system, opening the cooling system, and cooling the welding piece and the heating platform.
Specifically, the step S9 specifically includes:
step S91: when the temperature is cooled to 100-200 ℃, closing the vacuum baffle valve 230, and opening a nitrogen valve to fill nitrogen into the vacuum chamber 110;
step S92: when the PLC detects that the pressure in the vacuum chamber 110 reaches the normal pressure through the pressure sensor, the nitrogen valve is closed.
Specifically, the step S1 specifically includes:
step S11: firstly, writing the program of the whole welding process on an upper computer;
step S12: sending the welding process compiled on the upper computer to a PLC (programmable logic controller);
step S13: pressing the capsule opening button to open the upper cover or the capsule door of the vacuum capsule 110;
step S14: placing a workpiece to be welded or a tool with the workpiece to be welded on a heating platform;
step S15: after the upper cover or the hatch door of the vacuum chamber 110 is closed, the upper cover or the hatch door of the vacuum chamber 110 is locked by the upper cover or the hatch door locking cylinder 240 by pressing a closing button;
step S16: and pressing a start button to automatically run the program.
The results of the invention compared with the welding experiments of the traditional process are as follows (a total of 3 groups tested):
test one (in one set):
and (3) testing equipment: vacuum reflow soldering GYY-3023T;
protective gas: n is a radical of 2 ；
Welding materials: brand name: thousands of people; the model is as follows: m705; the components: SN96.5AG3.0CU0.5, respectively; melting point: 217 deg.C; peak temperature: at 255 deg.c.
The X-RAY detection result graph of the weldment obtained by adopting the traditional process is shown in figure 7-a, the X-RAY detection result graph of the weldment obtained by adopting the process of the invention is shown in figure 8-a, and the graph shows that the voidage of the weldment obtained by the process of the invention is obviously improved, through tests, the voidage of the weldment obtained by the traditional process of the group of tests is more than 3.7 percent, and the voidage of the weldment obtained by the invention is lower than 1 percent and is close to zero.
Test two (two sets):
testing equipment: vacuum reflow soldering GYY-3023T;
protective gas: h 2 ；
Welding materials: brand name: thousands of people; the components: a gold-tin soldering lug; melting point: 280 ℃; peak temperature: at 320 ℃.
The X-RAY detection result graph of the weldment obtained by adopting the traditional process is shown in figures 7-b and 7-c, the X-RAY detection result graph of the weldment obtained by adopting the process of the invention is shown in figures 8-b and 8-c, and the graph shows that the voidage of the weldment obtained by adopting the process of the invention is obviously improved, and through tests, in two groups of tests, the voidage of the weldment obtained by adopting the traditional process is more than 2.5 percent, and the voidage of the weldment obtained by adopting the process of the invention is lower than 1 percent and is close to zero.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.
Claims (6)
1. A positive and negative pressure combined welding process for vacuum reflow soldering is characterized by comprising the following steps:
step S1: debugging equipment of a vacuum chamber;
step S2: the method comprises the following steps that a PLC (programmable logic controller) controls a vacuum baffle valve to be opened, vacuumizing is started at a normal temperature, the vacuumizing time is 10-120 seconds, and when the PLC detects that the pressure in a vacuum cabin is less than or equal to a preset pressure value of negative pressure 0.05-100 PA through a pressure sensor, the vacuum baffle valve is closed;
step S3: opening a reducing agent valve by a PLC (programmable logic controller), filling a reducing agent into the vacuum chamber to a positive pressure of 1000-500000 PA (Power Amplifier) under a normal temperature state, and closing the reducing agent valve when the PLC detects that the positive pressure value in the vacuum chamber reaches 1000-500000 PA through a pressure sensor;
step S4: heating to 160-180 ℃;
step S5: then heating to the melting point of the solder of 217 ℃ for 60-120 seconds;
step S6: heating to 245-260 ℃ and keeping the temperature for 1-30 seconds;
step S7: then, a vacuum baffle valve is opened through a PLC controller, vacuumizing is carried out for 20-30 seconds, and the vacuum degree in a vacuum chamber is maintained at negative pressure of 0.01-100 PA;
step S8: cooling;
step S9: the internal pressure of the vacuum chamber reaches the normal pressure;
step S10: when the preset cooling temperature is detected, the cooling system is closed to stop cooling, the cabin opening button is pressed, the upper cover or the cabin door of the vacuum cabin is opened, and the weldment is taken out;
in step S3, the reducing agent is N 2 Formic acid, H 2 CO or N 2 +H 2 Any one of the mixed gases;
when the reducing agent is H 2 CO or N 2 +H 2 In the case of any one of the mixed gases, the following steps are further included between step S6 and step S7:
step A: starting a gas combustion device through a PLC (programmable logic controller) at a constant temperature of 245-260 ℃ to combust and discharge the generated reductive combustible gas;
the gas combustion device comprises a cooling cylinder, the cooling cylinder is used for being connected with a gas pipeline, the top of the cooling cylinder is connected with a burner, the top of the cooling cylinder is connected with a plurality of support columns which are arranged around the burner, the top of each support column is provided with a housing, the housing is of a hollow structure, the top of the burner is positioned in the housing, the housing is provided with a pulse igniter close to the top of the burner, the side wall of the cooling cylinder is provided with a lifting cylinder, the top of the lifting cylinder is provided with an igniter and a temperature sensor, one end of the igniter is close to the top of the burner and an ignition end of the pulse igniter, one end of the temperature sensor is close to the top of the burner, the side wall of the housing is provided with a movable port, the igniter penetrates through the movable port and can move up and down in the movable port, the top of the housing is provided with a combustion chamber, and the top of the combustion chamber is provided with an exhaust fan;
the step A specifically comprises the following steps:
step A1: the PLC controller controls the lifting cylinder to enable the igniter to descend, the pulse igniter is used for igniting the igniter, and when the PLC controller detects that the igniter burns normally through the temperature sensor, the PLC controller controls the lifting cylinder to enable the igniter to ascend to the position above the combustion nozzle;
step A2: discharging air of the gas pipeline to the outside of the burner;
step A3: the PLC controller controls a baffle valve of the gas combustion device to be opened;
step A4: the PLC controls a nitrogen valve to be opened, and nitrogen is filled from the bottom of the vacuum chamber;
step A5: and when the nitrogen gas filling amount is detected to be larger than or equal to the volume in the vacuum cabin, closing the gas combustion device.
2. A vacuum reflow positive and negative pressure combination soldering process in accordance with claim 1, wherein when the reducing agent is H 2 CO or N 2 +H 2 In the case of any of the mixed gases, the following steps are further included between step S2 and step S3:
step a: the PLC controls the nitrogen filling valve to be opened, nitrogen is filled into the vacuum chamber at normal temperature, and when the PLC detects that the pressure in the vacuum chamber reaches a normal pressure value through the pressure sensor, the nitrogen filling valve is closed;
step b: the method comprises the steps that a PLC (programmable logic controller) controls a vacuum baffle valve to be opened, vacuumizing is started at a normal temperature, the vacuumizing time is set to be 10-120 seconds, and when the PLC detects that the pressure in a vacuum cabin is less than or equal to a preset pressure value of negative pressure of 0.05-100 PA through a pressure sensor, the vacuum baffle valve is closed;
step c: and (c) repeating the step a and the step b, and converting oxygen molecules in the vacuum cabin out of the cabin until the process requirement of the weldment on the oxygen molecule content is met.
3. The positive-negative pressure bonding process of claim 1, wherein the heating ramp rate is 1.5-3 ℃/sec in step S4, and 1-3 ℃/sec in step S6.
4. The vacuum reflow positive-negative pressure combination soldering process according to claim 1, wherein the step S8 is specifically as follows:
and under the condition that the vacuum degree is maintained at the negative pressure of 0.01-100 PA, closing the heating system, opening the cooling system, and cooling the welding piece and the heating platform.
5. The vacuum reflow positive-negative pressure combination soldering process according to claim 1, wherein the step S9 specifically includes:
step S91: when the temperature is cooled to 100-200 ℃, closing the vacuum baffle valve, and opening a nitrogen valve to fill nitrogen into the vacuum chamber;
step S92: and when the PLC detects that the pressure in the vacuum chamber reaches the normal pressure through the pressure sensor, the nitrogen valve is closed.
6. The vacuum reflow positive-negative pressure combination soldering process according to claim 1, wherein the step S1 specifically includes:
step S11: firstly, writing the program of the whole welding process on an upper computer;
step S12: sending the welding process compiled on the upper computer to a PLC (programmable logic controller);
step S13: pressing down a cabin opening button to open an upper cover or a cabin door of the vacuum cabin;
step S14: placing a workpiece to be welded or a tool with the workpiece to be welded on a heating platform;
step S15: after an upper cover or a cabin door of the vacuum cabin is closed, a cabin closing button is pressed, and the upper cover or the cabin door locking cylinder locks the upper cover or the cabin door of the vacuum cabin;
step S16: and pressing a starting button to automatically run the program.
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