A wave soldering process for PCB board and PCB board obtained by soldering

Abstract

The present application discloses a wave soldering process for a PCB board and a PCB board obtained by soldering, and relates to the field of soldering technology. The process includes placing a PCB board to be soldered on a fixed fixture, and spraying flux on the PCB board; after the spraying is completed, the PCB board is transported by a conveying device through a preheating zone for preheating and then enters a soldering zone; wherein, the copper content in the solder in the soldering zone is detected within a preset period, the copper content in the solder is compared with the preset copper content, and the amount of copper powder added in the soldering zone is adjusted according to the comparison result; the soldered PCB board enters a cooling zone for cooling; after the cooling is completed, the soldered PCB board is output. The present application can prevent the problem of batch product scrapping caused by failure of electrical connection of the PCB board due to corrosion of the PCB pad by controlling the value range of the influencing factors in the wave soldering process, so as to ensure that the thickness of the copper pad is above the industry electrical connection standard thickness.

Description

Technical Field

[0001] The present application relates to the technical field of welding, and in particular to a wave soldering process for a PCB board and a PCB board obtained by soldering. Background Art

[0002] Wave soldering technology, wave soldering refers to the process of molten soft solder (lead-tin or lead-free alloy) being sprayed into a solder wave peak as required by the design through an electric pump or an electromagnetic pump. It can also be formed by injecting nitrogen into the solder pool, so that a printed circuit board (PCB board) pre-installed with components passes through the solder wave peak, thereby achieving soft soldering of mechanical and electrical connections between the component terminals or pins and the PCB board; copper corrosion refers to the process in which the solder corrodes and dissolves the copper pads on the PCB board when it contacts the PCB board during wave soldering. When the pads are corroded to a certain extent, the electrical connection of the PCB board will fail.

[0003] PCB board with components is called circuit board assembly or PCBA. The components on the board can be surface mount components, plug-in components, pressed components or assembly parts. The wave soldering process is to load the PCBA with plug-in components on the fixture, pass through the flux spray system, preheating section and tin bath of the tin furnace in sequence through the conveyor belt, contact with the tin liquid in the tin bath to complete the welding, and then complete the whole wave soldering process through the cooling system.

[0004] In the actual welding process, due to different welding process conditions, when the printed circuit board is in the wave soldering process, the pad on the PCB board will be corroded by the solder when passing through the solder wave. If the pad thickness is lower than the lower limit of the industry electrical connection, the circuit board will fail and be scrapped. Based on the above problems, a better process condition is urgently needed to ensure that the thickness of the copper pad of the PCB material is above the industry electrical connection standard thickness when passing through the lead-free solder wave. Summary of the invention

[0005] In order to solve at least one of the problems mentioned in the above background technology, the present application provides a wave soldering process for a PCB board and a PCB board obtained by welding, which can prevent the problem of batch product scrapping caused by failure of electrical connection of the PCB board due to corrosion of the PCB pad by controlling the value range of the influencing factors in the wave soldering process, so as to ensure that the thickness of the copper pad is above the industry electrical connection standard thickness.

[0006] The specific technical solutions provided by the embodiments of this application are as follows:

[0007] In a first aspect, a PCB wave soldering process is provided, the process comprising:

[0008] Placing the PCB to be soldered on a fixed fixture and spraying flux on the PCB;

[0009] After spraying is completed, the PCB board is transported by a conveying device through a preheating zone for preheating and then enters a welding zone;

[0010] The copper content in the solder of the welding zone is detected within a preset period, the copper content in the solder is compared with a preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result;

[0011] The soldered PCB board enters the cooling area for cooling;

[0012] After cooling is completed, the PCB board after welding is output.

[0013] In a specific embodiment, the process further includes compensating the PCB board in the preheating zone, specifically including:

[0014] Temperature compensation for the PCB board after the waste heat, including:

[0015] Detecting the temperature of the surface of the PCB board by using a furnace temperature meter;

[0016] Comparing the temperature of the surface of the PCB board with the preheating temperature;

[0017] If the temperature of the surface of the PCB is lower than the preheating temperature, a heating furnace is set to continue heating the PCB so that the surface temperature of the PCB reaches the preheating temperature.

[0018] In a specific embodiment, the process further comprises:

[0019] Set the preheating temperature of the preheating zone to 95℃~120℃;

[0020] Preferably, the preheating temperature of the preheating zone is 100°C to 115°C.

[0021] In a specific embodiment, the process further comprises:

[0022] Set the chain speed of the conveyor device to 50cm / min~120cm / min;

[0023] Preferably, the chain speed of the conveyor is 65 cm / min to 100 cm / min.

[0024] In a specific embodiment, the process further comprises:

[0025] Setting the preset copper content range to: 0.5% to 0.9%;

[0026] Preferably, the preset copper content range is: 0.55% to 0.8%.

[0027] In a specific embodiment, the copper content in the solder of the welding area is detected within a preset period, and the amount of copper powder added is adjusted according to the detection result, which specifically includes:

[0028] Detecting the copper content in the solder at preset time intervals, and comparing the copper content in the solder with the preset copper content range of 0.55% to 0.8%;

[0029] When the copper content in the solder is less than 0.55%, copper powder is added to the solder;

[0030] When the copper content in the solder is greater than 0.8%, part of the solder is replaced with copper-free solder;

[0031] When the copper content in the solder is between 0.55% and 0.8%, the copper content in the solder is not adjusted.

[0032] In a specific embodiment, when the copper content in the solder is less than 0.55%, the weight of copper powder added to the solder is m1-m2, specifically:

[0033] m1=m0*(0.55%-w)

[0034] Wherein, m1 is the minimum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected;

[0035] m2=m0*(0.80%-w)

[0036] Among them, m2 is the maximum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; and w is the copper content in the solder detected.

[0037] In a specific embodiment, when the copper content in the solder is greater than 0.8%, the weight of the replaced part of the solder is G1-G2, specifically:

[0038]

[0039] Wherein, G1 is the minimum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected;

[0040]

[0041] Among them, G2 is the maximum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected.

[0042] In a specific embodiment, the process further comprises:

[0043] Setting the solder temperature of the soldering zone to 250°C to 270°C;

[0044] Preferably, the solder temperature of the welding zone is 260°C to 265°C.

[0045] In a second aspect, a PCB board is provided, wherein the PCB board is obtained by welding according to the PCB board wave soldering process.

[0046] The embodiments of the present application have the following beneficial effects:

[0047] 1. The embodiment of the present application provides a method of placing a PCB board to be welded on a fixed fixture, and then spraying flux on the PCB board. After the spraying is completed, the PCB board is transported through a preheating zone by a conveying device for preheating. When the surface of the PCB board reaches the preheating temperature, it enters the welding zone. During the welding process, the content of copper powder needs to be controlled. Specifically, the copper content in the solder in the welding zone is detected within a preset period, the copper content in the solder is compared with the preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result; the welded PCB board enters a cooling zone for cooling, and the welded PCB board is output after cooling. In the present application, the range of each parameter in the welding process is controlled, and the amount of copper powder added is carefully adjusted by a control method, so as to prevent the problem of batch product scrapping caused by failure of electrical connection of the PCB board due to PCB pad clothing, so as to ensure that the thickness of the copper pad is above the industry electrical connection standard thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0049] Figure 1 A schematic diagram of a PCB wave soldering process according to the present application is shown. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0051] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0053] As described in the background technology, in the actual welding process, due to different welding process conditions, when the printed circuit board is in the wave soldering process, the pads on the PCB board will be corroded by the solder when passing through the solder wave. If the pad thickness is lower than the industry electrical connection lower limit, the circuit board will fail and be scrapped. Based on the above problems, there is an urgent need for a better process condition that can ensure that the thickness of the copper pad of the PCB material is above the industry electrical connection standard thickness when passing through the lead-free solder wave. Based on the above problems, the present application proposes a PCB wave soldering process and a PCB board obtained by welding.

[0054] Embodiment 1

[0055] A PCB wave soldering process, such as Figure 1 As shown, the process includes the following steps:

[0056] Step S1: placing a PCB to be soldered on a fixed fixture, and spraying soldering flux on the PCB.

[0057] Specifically, the PCB circuit board with components already inserted is embedded in the jig, and is sent into the wave soldering machine at a preset inclination angle and conveying speed by the docking device at the entrance of the machine. It is then clamped by the continuously running chain claws and sensed by the sensor. The nozzle sprays back and forth at a uniform speed along the starting position of the jig, so that the exposed pad surface of the circuit board, the pad via hole and the surface of the component pin are evenly coated with a thin layer of flux.

[0058] Step S2: After spraying is completed, the PCB board is transported by a conveying device through a preheating zone for preheating and then enters a welding zone.

[0059] In a specific embodiment, the preheating temperature of the preheating zone is set to 95°C ~ 120°C by a furnace temperature tester, and the PCB board is heated by adjusting each heating zone module of the wave soldering. Preferably, the preheating temperature of the preheating zone is 100°C ~ 115°C.

[0060] In a specific embodiment, after the PCB board enters the preheating area, the welding part of the PCB board is heated to the wetting temperature. At the same time, due to the increase in the temperature of the components, a large thermal shock when immersed in molten solder is avoided. The temperature of the preheating zone is specifically set to 100°C ~ 115°C.

[0061] In a specific embodiment, the chain speed of the transmission device is set to 50cm / min to 120cm / min by directly inputting the speed value control; preferably, the chain speed of the conveying device is 65cm / min to 100cm / min, thereby realizing the conveying of the PCB board by the conveying device within a suitable speed range.

[0062] In a specific embodiment, the process also includes compensating the PCB board in the preheating zone, specifically including: detecting the surface temperature of the PCB board through a furnace temperature meter; comparing the surface temperature of the PCB board with the preheating temperature; if the surface temperature of the PCB board is lower than the preheating temperature, setting a heating furnace to continue heating the PCB to achieve the surface temperature of the PCB board reaching the preheating temperature. Specifically, the surface temperature of the PCB board detected by the furnace temperature meter is 95°C, at which time 95°C is lower than the lowest temperature of the preheating zone of 100°C, and it is necessary to set a heating furnace to continue heating the PCB board until the surface temperature of the PCB board detected by the furnace temperature meter reaches 100°C to 115°C, thereby confirming that the PCB board reaches the preheating temperature. Specifically, if the surface temperature of the PCB board detected by the furnace temperature meter is 110°C, at this time 110°C is within the preheating temperature range, that is, the PCB board reaches the preset temperature, so at this time, the welding area can be entered to weld the PCB board.

[0063] In a specific embodiment, the PCB board is preheated in the preheating zone and then enters the welding zone. The welding temperature is first set before welding. Wave soldering has a real-time temperature measurement function of a thermocouple, and the solder temperature is controlled according to the heating power output by the PID control. The solder temperature of the welding zone is specifically set to 250°C to 270°C; preferably, the solder temperature of the welding zone is 260°C to 265°C. At the same time, the amount of solder to be added is confirmed, and the content of copper powder in the solder is adjusted according to the amount of solder to be added.

[0064] Specifically, the copper content in the solder of the welding zone is detected within a preset period, the copper content in the solder is compared with a preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result.

[0065] In a specific embodiment, the amount of solder added in the first cycle is obtained, wherein the amount of solder in the second cycle is set to be the same as the amount of solder in the first cycle. When the first cycle of welding is completed, the time of the first cycle is specifically set to "one week". After the first cycle of welding is completed, the copper content in the solder of the welding area in the first cycle is detected, and the copper content in the solder in the first cycle is obtained through the detection. The data of the copper content obtained by the detection is compared with the preset copper content, and the amount of copper powder added in the welding area is adjusted according to the comparison result.

[0066] In a specific embodiment, the process further includes: setting the preset copper content range to: 0.5% to 0.9%; preferably, the preset copper content range is: 0.55% to 0.8%.

[0067] In a specific embodiment, the copper content in the solder of the welding area is detected within a preset period, and the amount of copper powder added is adjusted according to the detection result, which specifically includes:

[0068] The copper content in the solder is detected at preset time intervals, and the copper content in the solder is compared with the preset copper content range of 0.55% to 0.8%; when the copper content in the solder is less than 0.55%, copper powder is added to the solder; when the copper content in the solder is greater than 0.8%, part of the solder is replaced with copper-free solder; when the copper content in the solder is between 0.55% and 0.8%, the copper content in the solder is not adjusted.

[0069] In a specific embodiment, when the copper content in the solder is less than 0.55%, the weight of copper powder added to the solder is m1-m2, specifically:

[0070] m1=m0*(0.55%-w)

[0071] Wherein, m1 is the minimum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected;

[0072] m2=m0*(0.80%-w)

[0073] Among them, m2 is the maximum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; and w is the copper content in the solder detected.

[0074] Specifically, when it is detected that the copper content in the solder of the first cycle is less than 0.55%, the weight of copper powder added to the solder during the second cycle of welding is m1-m2.

[0075] In a specific embodiment, the copper content in the solder of the first week is detected in the second week, that is, the copper content in the solder of the first week is detected to be 0.4%. At this time, the copper content is 0.4%. Since 0.4% is less than the preset copper content of 0.55%, copper powder needs to be added to the solder; the weight m0 of the solder in the first week is further set to 50kg, and w is 0.4%. At this time, m1 is calculated to be 0.07kg according to the above formula, and m2 is calculated to be 0.2kg according to the above formula. Then, the weight of copper powder added to the solder during the welding process of the second week is 0.07-0.2kg. If the copper content in the solder of the first week is detected in the second week, and the copper powder content detected is 0.65%, the copper powder content detected at this time is within the preset content range, and the copper powder content in the solder does not need to be adjusted at this time. If the copper content in the solder of the first week is tested in the second week, the copper content in the solder in the first week is detected to be 0.87%. At this time, the copper content of 0.87% detected in the solder is greater than the preset maximum copper content of 0.8%. Therefore, it can be explained that the copper content in the solder at this time exceeds the preset copper content range. At this time, part of the solder needs to be replaced with copper-free solder to reduce the copper content in the solder.

[0076] In a specific embodiment, when the copper content in the solder is greater than 0.8%, the weight of the replaced part of the solder is G1-G2, specifically:

[0077]

[0078] Wherein, G1 is the minimum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected;

[0079]

[0080] Among them, G2 is the maximum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected.

[0081] Specifically, when the copper content of the solder in the first cycle is detected to be greater than 0.8%, a portion of the original solder is first removed during the second cycle of soldering, and then an equal weight of copper-free solder is added, wherein the weight of the removed original solder or the added copper-free solder is G1 to G2.

[0082] In a specific embodiment, the copper content of the first week is detected during the second week, that is, the copper content of the solder detected in the first week is 0.95%. At this time, the copper content of 0.95% exceeds the preset range of copper content of 0.55% to 0.8%, and the solder needs to be replaced according to the detected copper content. The weight m0 of the solder in the first week is continued to be set to 50kg, and w is 0.95%. At this time, G1 is calculated to be 0.079kg according to the above formula, and G2 is calculated to be 0.21kg according to the above formula. During the welding process of the second week, a part of the original solder is first taken out, and then the same weight of copper-free solder is added to the welding area. At this time, before welding in the second week, the weight of the original solder to be taken out is 0.079kg to 0.21kg, and the weight of the original solder taken out can be "0.08kg", "0.085kg", "0.09kg", "0.095kg", "0.18kg", "0.19kg", "0.20kg", etc. When the above weight of original solder is taken out, an equal weight of copper-free solder is added to the solder and then the soldering process is started again.

[0083] In a specific embodiment, the first wave of welding is a "turbulent" flow with a narrow nozzle with a fast flow rate, which has better penetration for the welding part with shadows. At the same time, the upward jet force of the turbulent wave allows the flux gas to be discharged smoothly, greatly reducing the defects of missed welding and insufficient vertical filling.

[0084] Step S3: The soldered PCB board enters the cooling zone for cooling.

[0085] Specifically, after welding is completed, the welded PCB board is cooled down through the cooling zone. The refrigeration system causes the temperature of the PCB board to drop sharply, thereby significantly improving the problems of cavitation and pad peeling generated during the production of lead-free solder eutectic.

[0086] Step S4: After cooling is completed, the PCB board after welding is output.

[0087] Through the above scheme, the PCB board to be welded is placed on a fixed fixture, and then the PCB board is sprayed with flux. After the spraying is completed, the PCB board is transported through the preheating zone by a conveying device for preheating. When the surface of the PCB board reaches the preheating temperature, it enters the welding zone. The content of copper powder needs to be controlled during the welding process. Specifically, the copper content in the solder in the welding zone is detected within a preset period, and the copper content in the solder is compared with the preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result; the welded PCB board enters the cooling zone for cooling, and the welded PCB board is output after cooling. In this application, by controlling the range of each parameter in the welding process and carefully regulating the amount of copper powder added by the control method, the problem of batch product scrapping caused by the failure of the electrical connection of the PCB board due to the PCB pad clothing is prevented, so as to ensure that the thickness of the copper pad is above the industry electrical connection standard thickness. The scheme in this application enables the problem of batch product scrapping caused by the failure of the electrical connection of the PCB board due to the corrosion of the PCB pad to be prevented by controlling the value range of the influencing factor in the wave soldering process, so as to ensure that the thickness of the copper pad is above the industry electrical connection standard thickness.

[0088] Embodiment 2

[0089] Corresponding to the above embodiments, the present application provides an experimental process of the welding process. The specific welding process is as follows: place the PCB board to be welded on a fixed jig, and spray flux on the PCB board. Specifically, the PCB circuit board with the components inserted is embedded in the jig, and is sent into the wave soldering machine at a preset inclination angle and transmission speed by the docking device at the entrance of the machine, and then clamped by the continuously running chain claw, and sensed by the sensor. The nozzle sprays back and forth at a uniform speed along the starting position of the jig, so that the exposed pad surface of the circuit board, the pad via hole and the surface of the component pin are evenly coated with a thin layer of flux. After the spraying is completed, the PCB board is transported through the preheating zone by the conveying device for preheating, and then enters the welding zone after preheating. The preheating temperature of the preheating zone is set to 110°C by the furnace temperature tester, and the PCB board is heated by adjusting the modules of each heating zone of the wave soldering. During the preheating process, the PCB board in the preheating zone is also compensated, specifically, the temperature of the surface of the PCB board is detected by a furnace temperature meter; the temperature of the surface of the PCB board is compared with the preheating temperature; if the temperature of the surface of the PCB board is lower than the preheating temperature, a heating furnace is set to continue heating the PCB to achieve the surface temperature of the PCB board reaching the preheating temperature. After the PCB board is preheated in the preheating zone, it enters the welding zone, and the welding temperature is first set before welding. Wave soldering has a real-time temperature measurement function of a thermocouple, and the solder temperature is controlled according to the heating power output by the PID control. The solder temperature of the welding zone is specifically set to 265°C. At the same time, the amount of solder to be added is confirmed, and the content of copper powder in the solder is adjusted according to the amount of solder to be added. The amount of solder added in the first cycle is obtained, wherein the amount of solder in the second cycle is set the same as the amount of solder in the first cycle. After the first cycle of welding is completed, the time of the first cycle is specifically set to "one week". After the first cycle of welding is completed, the copper content in the solder of the welding area in the first cycle is detected. The copper content in the solder in the first cycle is obtained through the detection, and the copper content data obtained by the detection is compared with the preset copper content. The amount of copper powder added in the welding area is adjusted according to the comparison result. The copper content in the solder is set to 0.6% in this process.

[0090] The same as in Example 1, the difference from Example 1 is that the parameter settings for each process condition are different, (1) the initial thickness of the copper pad is specifically set to 40um, the preheating temperature of the PCB board is 110°C, the copper content is set to 0.6%, the solder temperature is 265°C, and then different chain speeds are set. The data of the remaining thickness of the pad obtained by the above settings are shown in Table 1:

[0091] Table 1 Welding results obtained by welding process under different chain speed conditions

[0092]

[0093] It can be seen from the data test results in Table 1 that within a certain chain speed range, that is, when the chain speed is 60cm / min to 100cm / min, as the chain speed increases, that is, the time for the conveyor to transport the PCB board to be processed through the welding area, the preheating area, etc. is reduced, the wave soldering time of the PCB board to be processed is shortened. Therefore, under the condition that the welding strength remains unchanged, the welding strength of the PCB board is reduced due to the shortened time for the PCB board transported by the conveyor to pass through the welding area. Under the condition that other factors remain unchanged, the remaining thickness of the pad after wave soldering increases with the increase of the chain speed.

[0094] (2) Specifically, the initial thickness of the copper pad is set to 40um, the chain speed is set to 80cm / min, the copper content is set to 0.6%, the solder temperature is set to 265°C, and then different PCB board preheating temperatures are set. The data of the remaining thickness of the pad obtained by the above settings are shown in Table 2:

[0095] Table 2 Welding results obtained by welding process under different preheating temperature conditions

[0096]

[0097] From the data in Table 2, it can be seen that when the preheating temperature of the PCB board is between 100℃ and 120℃, as the preheating temperature of the PCB board increases, the remaining thickness of the pad ranges from 22.5um to 27.8um. ​​This proves that within the appropriate preheating temperature range, as the preheating temperature increases, the soldering speed of the wave soldering increases, so the remaining thickness of the pad decreases as the preheating temperature increases. However, the thickness of the remaining PCB board obtained after welding is also within the industry standard, which shows that the increase in the PCB preheating temperature will accelerate the copper corrosion speed of the pad, thereby reducing the thickness of the pad as the preheating temperature increases.

[0098] (3) Specifically, the initial thickness of the copper pad is set to 40um, the chain speed is set to 80cm / min, the copper content is set to 0.6%, and the PCB board preheating temperature is set to 110°C. Then, different solder temperatures are set. Specifically, the solder temperature range is set to 260°C to 270°C. The data of the remaining thickness of the pad obtained by the above settings are shown in Table 3:

[0099] Table 3 Welding results obtained by welding process under different solder temperature conditions

[0100]

[0101]

[0102] It can be seen from the data in Table 3 that when the solder temperature is in the range of 260℃~270℃, as the solder temperature increases, the remaining thickness of the pad decreases from 31.2um to 26.4um, but the remaining thickness of the solder is still within the industry standard range. Therefore, within the appropriate solder range, as the solder temperature increases, the corrosion of the pad by wave soldering is accelerated, so within a certain temperature range, as the solder temperature increases, the remaining thickness of the pad gradually decreases.

[0103] (4) Specifically, the initial thickness of the copper pad is set to 40um, the chain speed is set to 80cm / min, the solder temperature is set to 265°C, and the PCB board preheating temperature is set to 110°C. Then, different copper contents are set. Specifically, the copper content range is set to 0.5% to 0.8%. The data of the remaining thickness of the pad obtained by the above settings are shown in Table 4:

[0104] Table 4 Welding results obtained by welding process under different copper content solder conditions

[0105]

[0106]

[0107] It can be seen from the data in Table 4 that within the copper content range of the table, that is, the copper content range is 0.5% to 0.8%, and under the welding conditions of preheating temperature of 110°C, chain speed of 80 / cm / min, and solder temperature of 265°C, the original thickness of the copper pad is 40um. As the copper content in the solder increases, it can be found from the thickness data of the remaining pad that the thickness of the remaining pad also gradually increases. The remaining thickness of the pad increases from 6.2um to 28.4um, further verifying that the degree of corrosion will decrease with the increase of copper content. In the experiment, when the copper content is less than or equal to 0.54%, the remaining thickness of the pad is 13.2um and 6.2um, respectively, and the remaining thickness of the pad does not meet the standard, which shows that the copper content in the solder needs to be controlled above 0.54%.

[0108] (5) Based on the test process in (1) to (4), it can be seen that the higher the preheating temperature of the PCB board, the faster the pad corrodes; the lower the chain speed, the faster the pad corrodes; the higher the solder temperature, the faster the pad corrodes; the lower the copper content in the solder, the faster the pad corrodes. Based on the above results, welding processes with different conditions are set, as shown in Table 5:

[0109] Table 5 Welding results obtained by welding process under comprehensive solder conditions

[0110]

[0111] Based on the test results in Table 5, the initial thickness of the PCB pad provided by the customer is 40um, and when the copper content in the solder is greater than or equal to 0.55%, the welding temperature is less than or equal to 265℃, the chain speed is greater than or equal to 65cm / min, and the PCB preheating temperature is less than or equal to 115℃, the remaining thickness of the pad is greater than or equal to 12.7um, that is, the remaining pad thickness is within the industry standard. The optimal conditions for the welding process are: the copper content in the solder ranges from 0.55% to 0.8%, the PCB board preheating temperature ranges from 100℃ to 115℃, the chain speed ranges from 65cm / min to 100cm / min, and the solder temperature ranges from 260℃ to 265℃.

[0112] Through the above scheme, the PCB board to be welded is placed on a fixed fixture, and then the flux is sprayed on the PCB board. After the spraying is completed, the PCB board is transported through the preheating zone by a conveying device for preheating. When the surface of the PCB board reaches the preheating temperature, it enters the welding zone. During the welding process, the content of copper powder needs to be controlled. Specifically, the copper content in the solder in the welding zone is detected within a preset period, the copper content in the solder is compared with the preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result; the welded PCB board enters the cooling zone for cooling, and the welded PCB board is output after cooling. In this application, the range of each parameter in the welding process is controlled, and the amount of copper powder added is carefully adjusted by the control method, so as to prevent the problem of batch product scrapping caused by the failure of the electrical connection of the PCB board due to the PCB pad clothing, so as to ensure that the thickness of the copper pad is above the industry electrical connection standard thickness.

[0113] Embodiment 3

[0114] A PCB board is provided, wherein the PCB board is obtained by welding according to the PCB board wave soldering process as described above, and the process comprises:

[0115] Placing the PCB to be soldered on a fixed fixture and spraying flux on the PCB;

[0116] After spraying is completed, the PCB board is transported by a conveying device through a preheating zone for preheating and then enters a welding zone;

[0117] The copper content in the solder of the welding zone is detected within a preset period, the copper content in the solder is compared with a preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result;

[0118] The soldered PCB board enters the cooling area for cooling;

[0119] After cooling is completed, the PCB board after welding is output.

[0120] In a specific embodiment, the PCB board in the preheating zone is compensated, specifically including: detecting the surface temperature of the PCB board by a furnace temperature meter; comparing the surface temperature of the PCB board with the preheating temperature; if the surface temperature of the PCB board is lower than the preheating temperature, setting a heating furnace to continue heating the PCB so that the surface temperature of the PCB board reaches the preheating temperature.

[0121] In a specific embodiment, the preheating temperature of the preheating zone is set to 95°C to 120°C; preferably, the preheating temperature of the preheating zone is 100°C to 115°C.

[0122] In a specific embodiment, it also includes: setting the chain speed of the conveying device to 50 cm / min to 120 cm / min; preferably, the chain speed of the conveying device is 65 cm / min to 100 cm / min.

[0123] In a specific embodiment, the preset copper content range is set to 0.5% to 0.9%; preferably, the preset copper content range is 0.55% to 0.8%.

[0124] In a specific embodiment, the copper content in the solder of the welding area is detected within a preset period, and the amount of copper powder added is adjusted according to the detection result, specifically including: detecting the copper content in the solder at each preset time interval, and comparing the copper content in the solder with the preset copper content range of 0.55% to 0.8%; when the copper content in the solder is less than 0.55%, copper powder is added to the solder; when the copper content in the solder is greater than 0.8%, part of the solder is replaced with copper-free solder; when the copper content in the solder is between 0.55% and 0.8%, the copper content in the solder is not adjusted.

[0125] In a specific embodiment, when the copper content in the solder is less than 0.55%, the weight of copper powder added to the solder is m1-m2, specifically:

[0126] m1=m0*(0.55%-w)

[0127] Wherein, m1 is the minimum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected;

[0128] m2=m0*(0.80%-w)

[0129] Among them, m2 is the maximum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; and w is the copper content in the solder detected.

[0130] In a specific embodiment, when the copper content in the solder is greater than 0.8%, the weight of the replaced part of the solder is G1-G2, specifically:

[0131]

[0132] Wherein, G1 is the minimum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected;

[0133]

[0134] Among them, G2 is the maximum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected.

[0135] In a specific embodiment, it also includes: setting the solder temperature of the welding zone to 250°C to 270°C; preferably, the solder temperature of the welding zone is 260°C to 265°C.

[0136] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A PCB wave soldering process, characterized in that: The process comprises: Placing the PCB to be soldered on a fixed fixture and spraying flux on the PCB; After spraying is completed, the PCB board is transported by a conveying device through a preheating zone for preheating and then enters a welding zone; The copper content in the solder of the welding zone is detected within a preset period, the copper content in the solder is compared with a preset copper content, and the amount of copper powder added in the welding zone is adjusted according to the comparison result; Wherein, the preset copper content range is set to: 0.55% to 0.8%, the copper content in the solder is detected at each preset time interval, and the copper content in the solder is compared with the preset copper content range of 0.55% to 0.8%; when the copper content in the solder is less than 0.55%, copper powder is added to the solder; when the copper content in the solder is greater than 0.8%, part of the solder is replaced with copper-free solder; when the copper content in the solder is between 0.55% and 0.8%, the copper content in the solder is not adjusted; The soldered PCB board enters the cooling area for cooling; After cooling is completed, the PCB board after welding is output.

2. The PCB wave soldering process according to claim 1, characterized in that: The process also includes compensating the PCB board in the preheating zone, specifically including: Detecting the temperature of the surface of the PCB board by using a furnace temperature meter; Comparing the temperature of the surface of the PCB board with the preheating temperature; If the temperature of the surface of the PCB is lower than the preheating temperature, a heating furnace is set to continue heating the PCB so that the surface temperature of the PCB reaches the preheating temperature.

3. The PCB wave soldering process according to claim 2, characterized in that: The process also includes: Set the preheating temperature of the preheating zone to 100℃~115℃.

4. The PCB wave soldering process according to claim 3, characterized in that: The process also includes: Set the chain speed of the conveyor to 65cm / min~100cm / min.

5. The PCB wave soldering process according to claim 1, characterized in that: When the copper content in the solder is less than 0.55%, the weight of copper powder added to the solder is m1-m2, specifically: m1=m0*(0.55%-w) Wherein, m1 is the minimum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected; m2=m0*(0.80%-w) Among them, m2 is the maximum weight of copper powder that needs to be added to the solder; m0 is the weight of the solder in the previous cycle; and w is the copper content in the solder detected.

6. The PCB wave soldering process according to claim 5, characterized in that: When the copper content in the solder is greater than 0.8%, the weight of the replaced solder is G1 to G2, specifically: Wherein, G1 is the minimum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected; Among them, G2 is the maximum weight of the solder that needs to be replaced; m0 is the weight of the solder in the previous cycle; w is the copper content in the solder detected.

7. The PCB wave soldering process according to claim 1, characterized in that: The process also includes: The solder temperature of the soldering area is set to 260°C to 265°C.

8. A PCB board, characterized in that: The PCB board is obtained by welding according to the PCB board wave soldering process according to any one of claims 1 to 7.

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