High-reliability reflow soldering method for perforated plug-in

Abstract

The invention discloses a high-reliability reflow soldering method for a perforated plug-in. The method comprises the following steps: determining the boundary dimensions of coaxial bonding pads and plug-ins on the front and back surfaces of a printed circuit board; calculating the theoretical soldering tin amount between the through hole and the plug-in of the printed circuit board according to the boundary dimension; calculating a volume parameter of a prefabricated welding ring matched with the plug-in according to the theoretical soldering tin amount; and according to the volume parameters of the prefabricated welding ring, selecting the prefabricated welding ring, assembling the printed circuit board, the plug-in and the prefabricated welding ring, and then performing reflow soldering. The theoretical soldering tin amount is calculated according to the size information of the through hole and the plug-in at the position to be welded, the prefabricated welding ring with the equivalent volume is adopted as a process auxiliary material, the plug-in pin extending out of the surface of the printed circuit board is sleeved with the prefabricated welding ring, and the surface-mounted element and the plug-in are fused and welded in the same production method. Precise control over the soldering tin amount of reliable welding of the perforated plug-in is achieved, the assembling efficiency of the perforated plug-in is improved, and the reject ratio of abnormal products such as insufficient soldering tin and excessive soldering tin is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic packaging, in particular to a high-reliability reflow soldering method for through-hole plug-in components. BACKGROUND

[0002] Through-hole plug-in technology is a traditional soldering technology in modern PCB manufacturing industry, which is favored by high-reliability military or aerospace products due to its strong mechanical connection strength and high power heat dissipation characteristics. Through-hole plug-in technology is mainly applied to through-hole plug-in component soldering scenarios, and its process method is only wave soldering or manual soldering technology, which has strong dependence on manual operation, complex process flow, high production cost, and cannot meet the process requirements of high-density substrate double-sided soldering. In order to adapt to the demand of product lightening and miniaturization, under the premise of ensuring the high reliability and high applicability of the product, the industry begins to try to mix and integrate surface mount components and through-hole plug-in components into the same process method, which is compatible with SMT production line, and realizes the mixed soldering of miniaturized high-density devices and through-hole plug-in components. This production method can greatly improve production efficiency, reduce 30% of the process flow, and reduce production cost. At present, the tin plating method of through-hole plug-in reflow soldering is generally steel mesh printing, selective coating or manual dot coating, but for the special mixed structure of through-hole plug-in components protruding from the front surface of the PCB, the conventional steel mesh printing process of SMT cannot be used, and selective coating or manual dot coating is prone to uneven soldering, which causes soldering defects such as less soldering, bridge connection and void, affects production efficiency and production quality, and makes the cost reduction advantage of through-hole reflow soldering lost. Therefore, for the soldering of through-hole plug-in components with special structure, a soldering tin amount control method for through-hole plug-in components is needed to improve production efficiency and production quality. SUMMARY

[0003] In view of the above problems of the prior art, the technical problem to be solved by the present application is to provide a high-reliability reflow soldering method for through-hole plug-in components. By calculating the theoretical soldering tin amount between the through-hole and the plug-in component according to the coaxial pads on the printed circuit board and the outer dimensions of the plug-in component, and calculating the volume parameter of the prefabricated solder ring according to the theoretical soldering tin amount, a prefabricated solder ring suitable for the plug-in component can be selected, and the precise control of the soldering tin amount can be realized.

[0004] The technical solution adopted by the present application is to provide a high-reliability reflow soldering method for through-hole plug-in components, which comprises the following steps: S1: determining the coaxial pads on the front and back surfaces of the printed circuit board and the outer dimensions of the plug-in component; S2: calculating the theoretical soldering tin amount between the through-hole of the printed circuit board and the plug-in component according to the outer dimensions; S3: calculating the volume parameter of the prefabricated solder ring suitable for the plug-in component according to the theoretical soldering tin amount; S4: selecting a prefabricated solder ring according to the volume parameter of the prefabricated solder ring, and assembling the printed circuit board, the plug-in component and the prefabricated solder ring, and then performing reflow soldering.

[0005] Further, the S1 step further comprises a dehumidification operation on the printed circuit board.

[0006] Further, the dehumidification operation is performed at a temperature of 120℃±5℃ for 4-7 hours.

[0007] Further, the S2 step is calculated as follows: ; ; ; ; wherein, represents the theoretical solder amount, represents the solder volume in the through hole, represents the actual solder climbing amount forming a meniscus climbing on the coaxial pad of the printed circuit board, represents the residual solder volume, and h represents the substrate thickness of the printed circuit board, represents the radius of the inner coaxial pad, represents the radius of the plug pin, represents half of the diameter of the plug pin, and is equivalent to , represents the average distance between the plug pin side surface and the outer edge of the outer coaxial pad, represents the radius of the outer coaxial pad.

[0008] Further, the S3 step is calculated as follows: ; ; ; L represents the actual number of turns of the preformed solder ring, represents the turn diameter of the preformed solder ring, C represents the turn circumference of the preformed solder ring, and A represents the cross-sectional area of the preformed solder ring wire, represents the diameter of the preformed solder ring wire.

[0009] Further, the turn diameter is 0.3-0.4mm larger than the diameter of the plug pin.

[0010] Further, the S4 step comprises the following sub-steps: S41: placing the plug to be soldered in the limiting hole of the reflow clamp; S42: placing the printed circuit board on the limiting step of the reflow clamp, so that the plug to be soldered passes through the through hole and extends out of the top surface of the printed circuit board; S43: according to the pre-made solder ring volume parameter, selecting a pre-made solder ring matched with the to-be-soldered plug and sleeving the pre-made solder ring on the to-be-soldered plug protruding from the top surface of the printed circuit board; S44: placing the reflow fixture together with the assembled printed circuit board in a reflow furnace for reflow soldering.

[0011] Further, the reflow fixture is made of hard aluminum, the limiting step is arranged at the top of the reflow fixture and used for placing the printed circuit board, and the limiting holes correspond to the through holes on the printed circuit board placed on the limiting step one by one.

[0012] Further, the reflow furnace is a hot air reflow furnace and includes ten independent temperature zones.

[0013] Further, the method further includes: S5: performing quality inspection on the soldered printed circuit board.

[0014] The perforated plug high-reliability reflow soldering method has at least the following beneficial effects: the perforated plug high-reliability reflow soldering method can 1. The pre-made solder ring has a low-cost manufacturing process and stable solid content, effectively controls the volume of solder in the through hole, and solves the process difficulty that the perforated plug cannot be printed, further effectively reduces the internal cavity of the perforated plug solder joint, and 2. The hot air reflow soldering of the perforated plug of the special structure of the module power supply product, the operator uses a specific pre-made solder ring to assemble the reflow, controls the solder amount of the perforated plug, forms a meniscus-shaped soldering surface climbing morphology meeting the quality standard of the national military standard, effectively reduces the defects of less solder and more solder, and avoids batch quality problems. BRIEF DESCRIPTION OF DRAWINGS

[0015] The drawings described herein are used to provide further understanding of the present application, constitute a part of the present application, the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1 The perforated plug high-reliability reflow soldering method is a flow chart of an embodiment of the present application.

[0016] Figure 2 The reflow fixture structure is a schematic view of an embodiment of the present application.

[0017] Figure 3 The soldering section is a schematic view of an embodiment of the present application.

[0018] Explanation of reference signs: ​Printed circuit board-1; coaxial pad-11; plug-in pin-2; reflow clamp-3; limiting step-31; limiting hole-32; meniscus climb-4; DETAILED DESCRIPTION The application will be further described below with reference to the drawings.

[0019] Please refer to Figure 1 , the flow chart of the high-reliability reflow soldering method for perforated plug-in. The high-reliability reflow soldering method for perforated plug-in includes the following steps: S1: Determine the coaxial pads 11 on the front and back of the printed circuit board 1 and the external dimensions of the plug-in; the external dimension data can be obtained by querying the substrate of the printed circuit board 1 and the material manual information of the plug-in in this S1 step. If there is no relevant information in the material manual information, the operator can measure the external dimension data through the three-dimensional drawing of the corresponding product. If there is no three-dimensional drawing, high-precision detection equipment can be used for actual measurement.

[0020] At the same time, it should be noted that, in order to remove the water vapor and local oxidation inside the circuit board, the printed circuit board 1 can also be dried and baked before this S1 step. The PCB board is baked in a constant temperature oven, and the baking parameters can be set as follows: the drying and baking temperature is 120±5℃, and the drying time is 6 hours.

[0021] S2: Calculate the theoretical soldering amount between the through hole of the printed circuit board 1 and the plug-in according to the external dimensions; The specific calculation method of this S2 step is as follows: ; ; ; ; Among them, represents the theoretical soldering amount, represents the soldering volume in the through hole, represents the actual soldering amount of the meniscus climb 4 formed at the coaxial pad 11 of the printed circuit board 1, represents the excess soldering volume, h represents the thickness of the substrate of the printed circuit board 1, represents the radius of the coaxial inner pad, represents the radius of the plug-in pin 2, Take half of the diameter of the plug-in pin 2, which is equivalent to , represents the average value of the distance between the side surface of the plug-in pin 2 and the outer edge of the coaxial outer pad, represents the radius of the coaxial outer pad.

[0022] It should be noted that, represents the volume of the soldering tin, which is the volume of the soldering tin produced by the capillary action of the soldering tin or the splashing and wetting in the actual assembly process, and accounts for about 30-40% of the expansion, i.e., the specific calculation method is as follows: or .

[0023] S3: calculating the volume parameter of the prefabricated solder ring matched with the insert according to the theoretical soldering tin amount; in this S3 step, the theoretical soldering tin amount of the insert pad meniscus climbing is obtained according to the above theoretical calculation, and the actual size of the prefabricated solder ring (ring) with the same volume is calculated by analogy.

[0024] The specific calculation method of this S3 step is as follows: ; ; ; wherein L represents the actual number of turns of the prefabricated solder ring, represents the turn diameter of the prefabricated solder ring, C represents the turn circumference of the prefabricated solder ring, and A represents the cross-sectional area of the prefabricated solder ring wire, represents the diameter of the prefabricated solder ring wire.

[0025] It is worth mentioning that the prefabricated solder ring can be made by winding the original soldering tin wire, and the solder composition is related to product demand, SnPbAg for low-temperature use, SnAgCu or SnAg for high-temperature use, the melting point of the prefabricated solder ring is the same as the melting point of the solder paste required by the product, which ensures that the prefabricated solder ring can be equivalent to the product reflow soldering in the reflow process.

[0026] The turn diameter of the prefabricated solder ring is about 0.3-0.4mm different from the diameter of the insert; The number of turns of the prefabricated solder ring is 0.5-3.5, and the weight precision is 0.001g.

[0027] S4: selecting a prefabricated solder ring according to the volume parameter of the prefabricated solder ring, and assembling the printed circuit board 1, the insert and the prefabricated solder ring, and then reflow soldering.

[0028] Please refer to Figures 2-3 , the present S4 step can include the following sub-steps: S41: placing the insert to be soldered in the limiting hole 32 of the reflow fixture 3; S42: placing the printed circuit board 1 on the limiting step 31 of the reflow fixture 3, so that the insert to be soldered passes through the through hole and extends out of the top surface of the printed circuit board 1. In the present S41 and S42 steps, in order to ensure that the insert can be placed stably in the limiting hole 32 of the reflow fixture 3, a common blocking ring design structure can be used on the insert; S43: According to the pre-made solder ring volume parameters, select a pre-made solder ring that fits the to-be-soldered insert, and fit the pre-made solder ring on the to-be-soldered insert that protrudes from the top surface of the printed circuit board 1; S44: Place the reflow fixture 3 together with the assembled printed circuit board 1 in a reflow oven for reflow soldering.

[0029] It should be noted that the printed circuit board 1 of the present scheme has the requirement of double-sided soldering, so when reflow soldering is performed, the two surfaces of the printed circuit board 1 need to be reflow soldered in turn. Therefore, when selecting the material of the pre-made solder ring, two materials with different melting points need to be selected, and the pre-made solder ring with a higher melting point is used for the surface of the printed circuit board 1 that is reflow soldered first, so as to ensure that the solder that has been soldered does not melt when the other surface of the printed circuit board 1 is reflow soldered.

[0030] In some embodiments, the reflow fixture 3 is made of hard aluminum, the limiting step 31 is opened at the top of the reflow fixture 3 for placing the printed circuit board 1, and the limiting hole 32 corresponds to the through hole on the printed circuit board 1 placed on the limiting step 31 one by one, so as to further fix the position of the printed circuit board 1 and the insert during the low-temperature reflow process of the insert.

[0031] In some embodiments, the reflow oven is a hot air reflow oven, which can realize a high-temperature hot air atmosphere in the oven, and the oven has ten temperature zones, each of which has independent temperature and can be adjusted according to the actual temperature to control the heating time of the product in each temperature zone and ensure good soldering quality.

[0032] S5: Inspect the printed circuit board 1 after soldering. In this S5 step, the inspector can use a body microscope to detect the soldering points of the assembled parts after soldering at a magnification of 5-45 to confirm whether they meet the quality level requirements of GJB3243 and GJB3835.

[0033] In summary, the complete steps of the present scheme are as follows: Step 1: Dry and bake the printed circuit board 1 using a constant-temperature oven, and the baking parameters are set as follows: dry and bake at a temperature of 120±5℃ for 6 hours. The purpose of baking is to remove the water vapor and local oxidation inside the circuit board; Step 2: Determine the coaxial pads 11 on the front and back surfaces of the printed circuit board 1 and the outer dimensions of the insert device. The actual size data can be obtained by querying the substrate and insert material manual information of the printed circuit board 1. If there is no relevant information in the material manual information, the operator can measure the size data through the three-dimensional drawings of the corresponding product. If there is no three-dimensional drawing, high-precision detection equipment can be used for actual measurement. Step 3, calculate the theoretical soldering amount required for through-hole welding, calculate the gap filling volume between the plug-in and the substrate, the actual soldering volume formed by the meniscus type climbing of the coaxial double-sided pads, and the excess soldering caused by the capillary action or splashing wetting in the reflow process, to obtain the theoretical soldering amount required for actual through-hole welding.

[0034] Step 4, based on the through-hole welding theoretical soldering amount obtained in step 3, the number of turns and the diameter of the pre-made solder ring are converted according to the relevant formula, but it should be noted that the diameter of the pre-made solder ring should be greater than the diameter of the plug-in pin 2, and the principle of facilitating the assembly of the plug-in pin 2 protruding from the surface of the substrate should be followed, and generally, the diameter of the solder ring is selected to be 0.3-0.4mm larger than the diameter of the plug-in pin 2, which is more appropriate, and the weight precision of the pre-made solder ring is controlled to be 0.001g. Step 5: According to the information of the plug-in to be welded and the corresponding product, find the corresponding reflow special fixture, which is made of hard aluminum and has a limiting hole 32 and a limiting step 31.

[0035] Step 6: Install the plug-in into the limiting hole 32 of the special fixture; Step 7: Put the substrate with through holes into the fixture, so that the plug-in pin 2 protrudes from the surface of the substrate through hole; Step 8: Put the pre-made solder ring prepared in step 4 on the plug-in pin 2 protruding from the surface of the substrate, and the pre-made solder ring is limited by the protruding plug-in pin 2; Step 9: Put the assembled product together with the fixture into the reflow oven for reflow soldering, and the pre-made solder ring melts under the action of high active flux during reflow, part of the solder flows into the gap between the plug-in and the substrate through hole, part of the solder forms a meniscus type climbing on the coaxial double-sided pads 11 of the substrate, and a small part of the solder is lost due to the capillary action or splashing wetting during reflow, and the solder solidifies after cooling, completing the reliable welding of the coaxial double-sided pads 11 of the through-hole plug-in; Step 10: Observe the surface appearance of the soldering point under a microscope to check the welding effect.

[0036] The present application provides a kind of through-hole plug-in high reliable reflow soldering method, by pre-baking treatment to printed circuit board 1 removes internal water vapor and reduces the risk of cavity caused by damp circuit board;The actual size of the pre-made solder ring obtained by theoretical calculation realizes the accurate control of the soldering amount required for low-temperature reflow soldering of through-hole plug-in, which improves the welding quality and reliability. At the same time, compared with manual spot coating solder paste, manual soldering or wave soldering, the operation is more convenient, the surface mounted components and plug-in are combined in the same production method, which reduces the production cost and is more efficient.

[0037] The above merely expresses the preferred embodiments of the present application, which are described in a more specific and detailed manner, but should not be understood as limiting the scope of the patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A high-reliability reflow soldering method for a through-hole component, characterized by, The method comprises the following steps: S1: determining the coaxial pads on the front and back surfaces of the printed circuit board and the external dimensions of the plug-in component; S2: calculating the theoretical soldering amount between the through hole of the printed circuit board and the plug-in component according to the external dimensions; S3: calculating the volume parameters of the prefabricated soldering ring adapted to the plug-in component according to the theoretical soldering amount; S4: selecting the prefabricated soldering ring according to the volume parameters of the prefabricated soldering ring, and assembling the printed circuit board, the plug-in component and the prefabricated soldering ring, and then performing reflow soldering.

2. The method of claim 1, wherein the method is a high-reliability reflow soldering method for a piercing insert, characterized by, The S1 step further comprises a moisture removal operation on the printed circuit board.

3. The method of claim 2, wherein the method is a high-reliability reflow soldering method for a piercing insert, characterized by, The moisture removal operation is performed at a temperature of 120℃±5℃ for 4-7 hours.

4. The method of claim 1, wherein the method is a high-reliability reflow soldering method for a piercing insert, characterized by, The specific calculation method of the S2 step is as follows: ； ； ； ； wherein, represents a theoretical solder volume, represents a volume of solder inside the through-hole, represents an actual solder volume of a meniscus-shaped wettability formed at a coaxial pad of a printed circuit board, represents a residual solder volume, h represents a substrate thickness of the printed circuit board, represents a radius of the coaxial inner pad, represents a radius of the plug pin, takes a half of the diameter of the plug pin, and is equivalent to , represents an average of a distance between a side surface of the plug pin and an outer edge of the coaxial outer pad, represents a radius of the coaxial outer pad.

5. The method of claim 4, wherein the soldering is performed by a reflow soldering process. The specific calculation method of the S3 step is as follows: ； ； ； wherein L represents the actual number of turns of the preformed welding ring, represents the diameter of the turns of the preformed welding ring, C represents the circumference of the turns of the preformed welding ring, and A represents the cross-sectional area of the preformed welding ring wire, represents the diameter of the preformed welding ring wire.

6. The method of claim 5, wherein the soldering is performed by a reflow soldering process. The winding diameter is 0.3-0.4mm larger than the pin diameter of the plug-in component.

7. The method of claim 1, wherein the method is a high-reliability reflow soldering method for a piercing insert. The S4 step comprises the following sub-steps: S41: placing the plug-in component to be soldered in the limiting hole of the reflow fixture; S42: placing the printed circuit board on the limiting step of the reflow fixture, so that the plug-in component to be soldered passes through the through hole and extends out of the top surface of the printed circuit board; S43: selecting the prefabricated soldering ring adapted to the plug-in component to be soldered according to the volume parameters of the prefabricated soldering ring, and sleeving the prefabricated soldering ring on the plug-in component to be soldered extending out of the top surface of the printed circuit board; S44: placing the reflow fixture together with the assembled printed circuit board in the reflow furnace for reflow soldering.

8. The method of claim 7, wherein the method is a high-reliability reflow soldering method for a piercing insert, characterized by, The reflow fixture is made of hard aluminum, and the limiting step is arranged on the top of the reflow fixture for placing the printed circuit board. The limiting hole corresponds to the through hole on the printed circuit board placed on the limiting step one by one.

9. The method of claim 7, wherein the method is a high-reliability reflow soldering method for a piercing insert, characterized by, The reflow furnace is a hot air reflow furnace comprising ten independent temperature zones.

10. The method of claim 1-9, wherein, The method further comprises: S5: performing quality inspection on the soldered printed circuit board.

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