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Conventional SMD mounting for PCBA manufacturing process
Features: small number of SMD components, the PCBA manufacturing process does not require high precision, the component varieties to resistor-capacitor-based.
SMD process:
1.Solder Paste Printing: Small semi-automatic printing machine is used for printing, manual printing is also available, but the quality of manual printing is worse than automatic printing.
2.PCBA manufacturing process mounting: generally can be used manually mounted, positional accuracy of some of the individual components can also be used in manual mounting machine mounting.
3.Welding: generally used reflow soldering process, special circumstances can also be used spot welding.
PCBA process of high-precision mounting
Features:FPC to have a substrate positioning MARK mark, FPC itself should be flat. FPC is difficult to fix, the consistency of mass production is more difficult to ensure that the equipment requirements are high.In addition,it is difficult to control the printing solder paste and mounting process.
Key process:FPC fixing: from printing and mounting to reflow soldering, the whole process is fixed on the pallet.The thermal expansion coefficient of the pallet should be small.There are two fixing methods, mounting accuracy for QFP lead spacing 0 or more methods.
A:Method used when the mounting accuracy is less than 0% of the QFP lead spacing.
B:Method A:The pallet is placed on the positioning template. The FPC is fixed to the pallet with a thin high-temperature tape, and then the pallet is separated from the positioning template for printing. The temperature-resistant tape should have a moderate viscosity,be easy to peel off after reflow, and have no adhesive residue on the FPC.
Solder Paste Printing:Since the FPC is mounted on the pallet, and there is a high temperature tape on the FPC for positioning,which makes the height inconsistent with the plane of the pallet, a flexible squeegee must be used for printing. The composition of the solder paste has a big influence on the printing effect, so it is necessary to choose the right solder paste.In addition,special treatment is required for printing templates using Method B.
Mounting equipment:Firstly, solder paste printing machine, the printing machine should be equipped with optical positioning system,otherwise the soldering quality will be greatly affected. Secondly, the FPC is fixed on the pallet, but the FPC and the pallet will always produce some small gap between the PCB substrate, which is the biggest difference. This is the biggest difference with the PCB substrate.The setting of equipments parameter will have a big impact on the printing effect, mounting accuracy and soldering effect. The mounting of FPCs requires strict process control.
PCBA manufacturing
Five special notes for PCBA moulding process
1.Preparation for PCBA processing
A.From the PMC or purchasing office to learn that a certain model is ready to test casting, you must know the development of the model responsible person and the person in charge of the biotechnology model, in order to obtain the relevant resources and help.
B.Borrow a sample machine: you need to make a simple understanding of the functions of the production model, and most have a good finished machine full-function test a few times.
C.Understand all the post-soldering components of the model, plan the post-soldering process, evaluate the post-soldering work and post-soldering notes.
D.Understand the use of test fixtures (often no test fixtures for the first trial production), planning test projects and processes.
E.Understand the layout of the PCB components, the characteristics of certain components to assess the production of attention.
F.Biotechnology needs to prepare the SMT data are ‘component location map’ ‘BOM table’ ‘schematic’, these data must be the same version of the PCB and production.
G.It is best to prepare a sample before departure.
2.In the PCBA hit parts processing plant material confirmation: material preparation and distribution of raw materials and technology have no power to intervene, but should be sent out to do a few confirmations, it is best to confirm with the development engineers:
A.First of all,to understand the situation of spare parts, whether or not the material will determine the production arrangements,not all the material to be immediately reverberated to the factory.
B.Confirmation of key materials, such as FW, IC, BGA,PCB boards and other major materials, version, material number and other confirmation.Material confirmation must be checked against the BOM.
C.General manufacturers IQC and material staff will also be on the material,if there is a discrepancy in the material should be immediately checked with the development engineers.
3.First piece confirmation
A.Patch the first confirmation, pay attention to the direction of the main components,specifications,check the SMT manufacturer's first record, while checking the template.
B.After the furnace PCB need to look at the individual components of the tin eating situation,the temperature resistance of the components.
C.After the soldering of the first piece of the best of their own hands to work, development engineers to confirm. At this time to start preparing for the production of post-soldering process and post-soldering SOP.
D. If there is a test fixture, test the first piece of their own personal test, development engineers to confirm the test project, start preparing the test project and test SOP.
4.Problem point tracking confirmation
Record and collate the entire production process occurs in the problem point, including data, materials, laminating, post-soldering, testing, maintenance, etc. all the PCBA playing pieces of the processing process, and summed up into a report on the traceability of the problem point, and in a timely manner with the person in charge of the production of SMT and the development of engineers to confirm the problem point.
5.Information feedback:PCBA hit parts processing should be completed after the problem echoed to the relevant personnel.
A.PCBA processing problem points echoed to the person in charge of biotechnology models, in order to review and improve.
B.Collect the SMT problems found in the factory trial casting and echo to the SMT person in charge.
C.Report back to SMT person in charge of the improvement of the test run problems.
D.Follow up the improvement of the problem points.
Attention for PCBA mass production
A certain type of machine in the same manufacturer has been many times in mass production, technology and process are more familiar with,some times or to pay attention to the following matters:
1.Test Fixture Confirmation:Confirmation of test fixtures and test accessories before production. Before the collection of problem points.
2.Confirmation of special materials:Confirmation of abnormal materials before production, and confirmation of materials on one occasion.
3.Confirmation of the first piece: A.Make a brief understanding of the first piece, test, and check the relevant first piece records. B.Check whether the previous problems occur again, and whether to improve. C.Confirmation of the previous PCBA playing pieces of processing procedures and processes need to be improved.
4.Analysis of defective products to confirm: to do a simple analysis of defective products,to understand the main distribution of defective and the main reasons for defective, and try to improve.
5.Information feedback: A.PCBA processing production problems echo back to the person in charge of biotechnology models to remind attention. B.Collect the assembly problem points in the factory and feedback to the person in charge for improvement.