CN116567954A

CN116567954A - Surface mounting technology for PCBA main board processing

Info

Publication number: CN116567954A
Application number: CN202310527129.7A
Authority: CN
Inventors: 黄欢; 房吉; 王震海
Original assignee: Suzhou Yinguang Electronic Co ltd
Current assignee: Suzhou Yinguang Electronic Co ltd
Priority date: 2023-05-11
Filing date: 2023-05-11
Publication date: 2023-08-08

Abstract

The invention relates to the technical field of PCBA main board processing, and discloses a surface mounting technology for PCBA main board processing, which comprises the following steps: step one: and preparing the process before pasting. The surface patch technology for PCBA main board processing realizes link-ring buckling of patches, is tightly connected with each other, is strictly implemented according to the standard in the operation process, greatly improves the quality of finished products, wherein when tin paste is printed, the tin paste is printed for two times before and after the tin paste is cleaned by professional cleaning equipment and continuously returns to a printing link when the tin paste does not pass detection, and the printing links at the front side and the rear side are only half of the common printing thickness, so that the required tin paste thickness can be achieved by adding, but the conditions of tin reduction, brush leakage, offset and tip pulling are greatly reduced in the two times of printing, and the subsequent repairing probability is further reduced.

Description

Surface mounting technology for PCBA main board processing

Technical Field

The invention relates to the technical field of PCBA main board processing, in particular to a surface mount technology for PCBA main board processing.

Background

Printed circuit boards, also called printed circuit boards, printed wiring boards, are important electronic components, are supports for electronic components, are providers for circuit connections of electronic components, and are called "printed circuit boards" because they are manufactured by adopting electronic printing technology, and before the occurrence of printed circuit boards, interconnections between electronic components are directly connected by wires to form complete circuits, and now, circuit boards exist only as effective experimental tools, and printed circuit boards have become an absolute dominant position in the electronic industry.

In order to realize functional operation of the circuit board, the bare board cannot be finished by one PCB, and the bare board is required to be subjected to component mounting, component inserting and welding, and the technological process of the step is called PCBA.

In the prior art, in the SMT paster process, the qualification rate of the circuit board is reduced due to various irregular works, and in the paster link, the solder paste is coated once, so that the PCB is subjected to a large number of conditions of tin reduction, missing printing, offset and pull tips, the quantity of the PCB is large in subsequent repair, and the productivity cannot keep up.

Therefore, there is a need for a surface mount technology for processing a PCBA motherboard, which solves the problems that in the prior art, in the process of SMT mounting, the qualification rate of a circuit board is reduced due to various non-standard operations, and in the mounting process, the solder paste is coated once, so that a large number of conditions of less tin, missing printing, offset and pull tip occur in the PCB due to one-time coating, so that the number of subsequent reworked PCBs is large, and the productivity cannot keep up with the problem.

Disclosure of Invention

The invention aims to provide a surface mounting process for PCBA mainboard processing, which aims to solve the problems that in the prior art, in the SMT mounting process, the qualification rate of a circuit board is reduced due to various irregular works, and in the mounting link, the solder paste is coated once, so that a large number of conditions of less tin, missing printing, offset and pull tips of a PCB occur due to one-time coating, the quantity of the subsequently repaired PCBs is large, and the productivity cannot keep up.

In order to solve the technical problems, the invention provides the following technical scheme: a surface mounting technology for PCBA motherboard processing comprises the following steps:

step one: preparing a process before pasting;

step two: the method comprises the steps of carrying out surface mounting, including upper plate, printing, detecting, repairing, device pasting and reinforcing, wherein the printing comprises primary printing and secondary printing, and repairing is carried out without equipment detection after the printing is finished, and comprises a complete repairing line;

step three: after the surface mounting is finished, the PCB enters reflow soldering in a 12-temperature area;

step four: detecting after welding, including AOI, intelligent first-piece tester and auxiliary detection by professional QC staff, if not, entering another repair line by PCB;

step five: and inspecting the mounted product.

Preferably, the preparing of the process in the first step includes making a production process folder according to the provided file and the BOM sheet, generating an SMT coordinate file, checking all production materials, confirming a PMC plan for production, entering the SMT program, making a head board for checking, and making a laser net surface according to the SMT process.

Preferably, the checking of the device is required between the patches in the second step, including:

s1: checking whether the air pressure of the chip mounter meets the equipment requirement, wherein the air pressure is generally 5kg/crri2;

s2: according to the width of the PCB, the width of a guide rail of the chip mounter is adjusted, the width of the guide rail is about 1mm larger than the width of the PCB, and the PCB is ensured to freely slide on the guide rail;

s3: setting and installing a PCB positioning device, setting a PCB positioning mode according to an operation rule, adopting a needle positioning mode, and installing and adjusting the position of a positioning needle according to the position of L in PCB positioning, wherein the positioning needle is exactly arranged in the middle of a positioning hole of the PCB, so that the PCB can be freely up and down;

s4: the PCB supporting thimble is arranged according to the thickness and the outline dimension of the PCB, so that the stress on the PCB is uniform and is not loosened during the surface mounting, the PCB is mounted on the double sides, and the position of the PCB supporting thimble must be readjusted after the surface mounting of the first surface is finished, so that the PCB supporting thimble avoids the components mounted on the surface B during the surface mounting of the second surface.

Preferably, in the second step, the PCB carrier and the PCB are sufficiently fixed, so that deviation of devices caused by deviation in SMT is prevented, after the mounting, laser marking is needed, unique serial numbers are marked on each PCB, the unique serial numbers are presented in the form of two-dimension codes, and information contained in the two-dimension codes mainly comprises production batches, circuit board models, manufacturer information and the like for products which are inquired and produced in later processes and later-stage SQE traceability defective products.

Preferably, the printing in the second step is to print solder paste on the PCB through the opened PCB steel screen template, and the printing comprises the following steps:

s1: adding solder paste onto the steel mesh by using a solder paste stirring knife, wherein the first solder paste adding height is about 1CM, the width is 1.5-2CM, the length is determined by the length of the PCB, and the two sides are about 3CM longer than the printing area, so that the solder paste is not suitable to be too long or too short; adding tin paste every two hours later, wherein the tin amount is about 100G;

s2: in the printing process, an operator needs to check the printing effect once every half hour to check whether the poor phenomena such as tin reduction, tin connection, pull tips, displacement, printing omission and the like exist, and check the printing effect on the pin too-dense element including heavy points such as BGA, QFP, SOP, row plug and the like;

s3: the printing thickness requirement is half of the conventional thickness, generally 0.4-0.8mm;

s4: during the printing process, the solder paste is checked periodically to check whether the solder paste overflows, and the overflowed solder paste is collected.

Preferably, the first printing in the second step is performed by the conveying equipment and is followed by the second printing, the second printing process is the same as the first printing, the printing thickness is half of the conventional thickness, and is generally 0.4-0.8mm, and the steel mesh adopted in the second printing is the steel mesh with the outer layer coated with the non-stick coating.

Preferably, the repairing route in the second step includes a transporting device, a cleaning device, an air drying device, and a scratch checking device, and includes the following steps:

s1: through SPI detection, transferring unqualified solder paste through a conveying device, entering a cleaning device for cleaning, avoiding the exposed part of the substrate, and cleaning the part coated with the solder paste;

s2: repeatedly cleaning tin paste by adopting alcohol and wiped dust-free paper, and after cleaning, airing in air-drying equipment, and drying by using an air gun, wherein the distance between the air gun and the substrate is 3-5cm;

s3: and (3) visual inspection or infrared inspection, namely detecting the substrate by using scratch detection equipment after no solder paste is determined to be remained, directly transporting the substrate to a printing process through detection, and entering another transportation line if the substrate cannot pass through detection.

Preferably, another repair line in the fourth step comprises a welding spot cleaning device, a transporting device, a cleaning device and a scratch checking device, the PCB which does not pass through the detection can enter the welding spot cleaning device through the transporting device, the welding spots are removed through melting, wiping and other steps, then the PCB is cleaned in the cleaning device, the foreign matters are prevented from being attached, then the scratch detection is carried out, the welding is carried out in the second step again through the transporting device, and the other transport line can be entered through the scratch detection.

Preferably, the checking in the fifth step includes:

s1: checking whether the specification, direction and polarity of the components on each component position number are consistent with those of the process file or the surface assembly template;

s2: checking whether the components are damaged or not and whether the pins are deformed or not;

s3: checking whether the mounting position of the component deviates from the bonding pad or not beyond an allowable range;

s4: the common spacing components can be visually inspected, and a magnifying glass, a microscope and on-line or off-line optical inspection equipment can be used at the time of high-density narrow spacing.

Compared with the prior art, the invention has the following beneficial effects:

firstly, the invention prepares the process before the patch, carries out the patch, and then the PCB enters the reflow soldering of the 12 temperature area after the patch is finished, detects after the welding is finished, and inspects the products after the patch is finished, thereby realizing the link ring of the patch, the link ring are mutually buckled, the connection is tight, and the quality of the finished product is greatly improved according to the standard implementation in the operation process, wherein when the solder paste is printed, the solder paste is printed for two times before and after the process passes the detection, and the printed solder paste is cleaned by professional cleaning equipment and then is continuously returned to the printing link, and the printing links at the front side and the rear side are only half of the common printing thickness, so the required solder paste thickness can be achieved by adding, but the conditions of less tin, brush leakage, offset and pull tip can be greatly reduced, the subsequent repair probability is further reduced, in addition, the influence on the original PCB is reduced as much as possible when the PCB is reworked, the rejection rate is reduced, and the cost is reduced.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a diagram of a single printing step according to the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Referring to fig. 1-2, a surface mount technology for processing a PCBA motherboard includes the following steps:

step one: preparing a process before pasting;

step five: and inspecting the mounted product.

According to the technical scheme, the process preparation before the pasting is carried out, the PCB enters the reflow soldering of the 12-temperature area after the pasting is finished, the detection is carried out after the welding is finished, and the products after the pasting are inspected, so that the link rings of the pasting are mutually buckled, the connection is tight, the quality of the finished product is greatly improved in the operation process according to the standard implementation, the printed solder paste is printed twice before and after the process is carried out, the printed solder paste is cleaned by professional cleaning equipment and then is continuously returned to the printing link when the solder paste does not pass through the detection, and the printing links at the front side and the rear side are only half of the common printing thickness, so that the required solder paste thickness can be achieved by adding, but the conditions of less tin, brush leakage, offset and tip pulling are greatly reduced in the two times, the subsequent repairing probability is further reduced, the influence on the original PCB is reduced as much as possible when the PCB is repaired, the rejection rate is reduced, and the cost is reduced.

Specifically, the process preparation in the first step comprises the steps of manufacturing a production process folder according to the provided file and the BOM sheet, generating an SMT coordinate file, checking all production materials, confirming a PMC plan for production, entering the SMT programming, manufacturing a head board for verification, and manufacturing a laser net surface according to the SMT process.

According to the technical scheme, the preparation work further comprises cleaning and baking treatment of the opened package PCB according to the length of the unsealing time and specific conditions such as whether the package is wet or polluted, the components are inspected after unsealing, the wetted components are treated according to the SMT process component management requirements, the shielded feeders are selected according to the specifications and types of the components, the component braiding feeders are correctly installed, the centers of the components are required to be aligned with the pick-up centers of the feeders during charging, the equipment matched with the chip mounter needs to be inspected, the air pressure of an air compressor is inspected to meet the equipment requirements, and is generally 6kgjf/cm < 2 > -7 kgf/cm < 2 >, and no obstacle is caused in the moving range of a guide rail, the mounting head, the periphery of an automatic replacement suction nozzle warehouse and a tray frame.

Specifically, the checking of the device between the patches in the second step includes:

According to the technical scheme, the feeder matched with the chip mounter is used for mounting various components on a material station of the chip mounter according to an off-line programming or on-line programming chip picking program table, and when the first component is subjected to test, the chip mounter has a plurality of chip mounting faults and is required to process according to specific conditions; a. failure to pick up a component, such as a component that is not picked up, may be considered to be inspected and processed as follows: the pick-up height is unsuitable, and the device thickness or Z-axis height is set incorrectly, and is corrected according to the actual value after inspection; the coordinates of the pick-up sheet are not suitable, and the feeder should be readjusted possibly because the feeding center of the feeder is not well adjusted; the plastic film of the braid feeder is not torn; the suction nozzle is blocked, and the suction nozzle is cleaned; dirt or cracks exist on the end face of the suction nozzle, so that air leakage is caused; the suction nozzle is unsuitable in model, if the L diameter is too large, air leakage can be caused, and if the aperture is too small, suction is insufficient; the air pressure is insufficient or the air channel is blocked, and whether the air channel leaks air, increases the air pressure or dredges the air channel is checked.

Specifically, in the second step, the PCB carrier and the PCB are fully fixed in the upper board process, deviation of devices caused by SMT is prevented, laser marking is needed after the upper board is arranged, unique serial numbers are marked on each PCB, the unique serial numbers are displayed in a two-dimensional code mode, and information contained in the two-dimensional codes mainly comprises production batches, circuit board models, manufacturing plant information and the like for products which are produced by subsequent flow inquiry and follow-up defective products of the later SQE.

According to the technical scheme, before solder paste printing, whether the steel mesh meets the standard or not is firstly determined, for example, stainless steel is used as a material, the thickness is 0.08+/-0.005 mm, SMT laser and electropolishing are carried out on the steel mesh, whether holes are blocked or not is checked, if the holes are blocked, the steel mesh is required to be cleaned by using dust-free paper to be stained with alcohol, and is blown dry by using an air gun, and the air gun is required to keep a certain distance with the steel mesh, so that the solder paste is required to have good activity and excellent tin climbing.

Specifically, the printing in the second step is to print solder paste onto the PCB through the opened PCB steel screen, and the printing comprises the following steps:

Through the technical scheme, the thickness of the primary printing is half of the conventional thickness, namely the PCB is firstly printed through the steel screen, although the thickness requirement is not met, the thickness requirement can be supplemented in the follow-up secondary printing, the condition that the secondary printing generally does not cause missing printing is remedied, the condition that the secondary printing causes missing printing and the condition of few printing is remedied, in the printing tin paste, the correct steel screen is required to be fixed on a printer and OK is debugged, then a clean and good scraper is assembled on the printer, the PCB is put into the PCB for printing, the whole inspection is required for the printed front 5PCS board, after the printing quality OK, the IPQC is notified for the first inspection, and after the fact that the printing quality is not abnormal is confirmed, the production line operators are notified to start production.

Specifically, the first printing in the second step is performed by the conveying equipment and is followed by the second printing, the second printing process is the same as the first printing, the printing thickness is half of the conventional thickness, and is generally 0.4-0.8mm, and the steel mesh adopted in the second printing is the steel mesh with the outer layer coated with the non-sticky coating.

Through the technical scheme, after coating production is finished, accessories and tools such as solder paste, a scraper, a steel mesh and the like are recovered, and the fixture is cleaned, and the operations are specifically performed according to the storage and use of solder paste and the cleaning operation guide of the steel mesh.

Specifically, the repairing route in the second step comprises a transportation device, a cleaning device, an air drying device and a scratch inspection device, and comprises the following steps:

Through the technical scheme, the PCB surface layer is not directly scraped by hard objects in the repairing process, so that the PCB surface layer circuit is prevented from being scratched, and the PCB with the golden finger is prevented from being scratched.

Specifically, another repair line in the fourth step comprises welding spot cleaning equipment, conveying equipment, cleaning equipment and scratch checking equipment, a PCB which does not pass through detection enters the welding spot cleaning equipment through the conveying equipment, the welding spots are removed through melting, wiping and other steps, then the PCB is cleaned in the cleaning equipment, the impurities are prevented from being attached, then the scratch detection is carried out, the welding is carried out in the second step again through the conveying equipment, and the other conveying line can be entered through the scratch detection.

By the technical scheme, the welding spots are cleaned without directly scraping the surface layer of the PCB by hard objects, so that the circuit of the surface layer of the PCB is prevented from being scratched, and if the device is welded, the device is also required to be taken out.

Specifically, the checking process in the fifth step includes:

Through the technical scheme, if the sheet discarding or frequent sheet discarding occurs, the following method can be adopted for processing: the image processing is incorrect, and the image should be re-shot; deforming pins of the components; the sizes, shapes and colors of the components are inconsistent, and the components packaged by the tube and the tray can be gathered together to re-photograph the images; the patch flies on the way due to unsuitable suction nozzle model, insufficient vacuum suction and the like; solder paste or other dirt is arranged on the end face of the suction nozzle, so that air leakage is caused; the end face of the suction nozzle is damaged or cracked, so that air leakage is caused.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit thereof, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The surface mounting technology for PCBA motherboard processing is characterized by comprising the following steps:

step one: preparing a process before pasting;

step five: and inspecting the mounted product.

2. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: the process preparation in the first step comprises the steps of manufacturing a production process folder according to the provided file and the BOM list, generating an SMT coordinate file, checking all production materials, confirming a PMC plan for production, entering SMT programming, manufacturing a head board for verification, and manufacturing a laser net surface according to the SMT process.

3. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: in the second step, the equipment needs to be checked between the patches, including:

4. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: in the second step, the PCB carrier and the PCB are fully fixed in the upper board process, deviation of devices caused by SMT is prevented, laser marking is needed after the upper board is arranged, unique serial numbers are marked on each PCB, the unique serial numbers are displayed in a two-dimensional code mode, and information contained in the two-dimensional codes mainly comprises production batches, circuit board models, manufacturing plant information and the like for products which are produced by subsequent flow inquiry and later-stage SQE tracing defective products.

5. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: the second step of printing is to print solder paste on the PCB through the opened PCB steel screen, and the first step of printing comprises the following steps:

6. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: the first printing in the second step is carried out by conveying equipment and is followed by the second printing, the second printing process is the same as the first printing, the printing thickness is half of the conventional thickness, and is generally 0.4-0.8mm, and the steel mesh adopted in the second printing is the steel mesh with the outer layer coated with the non-sticky coating.

7. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: the repairing route in the second step comprises a transportation device, a cleaning device, an air drying device and a scratch checking device, and comprises the following steps:

8. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: the other repair line in the fourth step comprises welding spot cleaning equipment, conveying equipment, cleaning equipment and scratch checking equipment, a PCB which does not pass through detection enters the welding spot cleaning equipment through the conveying equipment, the welding spots are removed through melting, wiping and other steps, then the PCB is cleaned in the cleaning equipment, the impurities are prevented from being attached, then scratch detection is carried out, the welding is carried out in the second step again through the conveying equipment, and the other conveying line can be entered through the scratch detection.

9. A surface mount process for PCBA motherboard processing as recited in claim 1, wherein: the checking process in the fifth step comprises the following steps: