This document tell you how we assembly 1000 PCB in SMT factory. It also let you know how we do mass production and avoid potential problems happens before we duplicate the mistake in mass production.
If you made PCB design, you must feel excited to solder components on it. It is usually take few hours to solder components on a PCB. If you need 100 boards, it may take days working with soldering iron and these boards. Besides, if you made any mistake during soldering process (i.e. short circuit, component shifted, non-wetting, etc). These mistake may cause hidden failure in functionality and it also cause spending extra time in debugging which can be double or triple of the time you spent in soldering.
In order to solder all components accurately, automated Pick and Place machine is necessary.
Step 1: Double Check Your Design
>>>>>This step is really important step <<<<<
- Make sure you are ready to start production
Since this is no return way after you start production, components will be degrade / damaged after de-soldering and those are not able to reuse in production line. Besides, manufacturing in factory is not always save you time and money. It just provide a standard way to do it automatically, if you supply the wrong stuff to factory. They definitely mess up your project.
Keep in mind that: Doing things right (Efficiency) and Doing the right things (Effectiveness).
- Design for manufacturing
As the Pick and Place machine only handle top side. It is recommend to have all components place on one side. It is possible to flip the board and run through the production line again, but cost will significantly increase.
- Check PCB layout design
In order to make 1000 pcs of PCBA, it is really important to make sure the PCB has no problem on design. If you made any mistake on design, it will inherit the issues to all boards! (i.e. Incorrect footprints, broken/short circuit, etc) You must make some samples and check detail before mass production.
- Well prepare the BOM (Bill Of Materials)
Detail BOM must included the following items:
- Complete part number
- Package / Component's Footprint
- Part's Designator / Part's Name
- Description of parts (Components specification i.e. Operating voltage/current, Tolerance, dimension, etc.)
- Manufacturer / Supplier (Component's brand)
- Populate (Component's footprint is available on PCB but no components solder on it)
- Distributor / Souring channel
The above information are important to prepare all the materials before manufacturing. It helps in estimate the total cost, sourcing components with schedule and plan, identify the component's position on PCB (Designator), etc.
Step 2: Prepare the Materials
Pay attention on the materials you supply to factory, as it may ruin your project if you buy wrong components. Some of the components are great for hand soldering but not good for automated production line. See below suggestion:
- All SMT (Surface mount technology) components required to have tube / tape and wheel packing / Tray packing, it means the components can put in SMT machine for production.
- Common parts (low cost) such as SMT resistors, capacitors, etc. please provide in complete tape and wheel packing
- Thur hole components such as pin, connectors, switches can provide in bulk package. (Avoid using thur hole components in design, as these components may raise production cost and lower yield rate)
- Semi-conductors components need special care, tape and wheel package. It is suggested to have ESD (Electrostatic Discharge) safe, Moisture-proof bag (vacuum sealed with dehydration) . (Normally you will get these package when you order from official suppliers)
- Components needs special care, please specify the needs for factories. (Such as Max Temperature of LED for soldering)
- If component has polarity i.e. Diodes, LEDs, etc. Please provide documents to identify the component's polarity on PCB. (As factories always confuse on the components polarity when they look at the PCB without label/mark on it)
- Reserved 1%-5% more components for manufacturing, since production loss is common in production line.
- PCB quality is important to avoid soldering issue, since the oxidized layer prevent soldering and cold joint may occur.
Step 3: Prepare the Golden Sample Before Manufacturing
It is suggest to make a working sample and well checked all functions. As all production units are identical to the golden sample. If you made any mistake in the sample, all mistake are inherited to every production units.
Please make sure the golden sample work without any problem.
Step 4: Start Production!
This is the most exciting step. The factory will collect all components and make sure all components quantities are ready for production.
Each PCBA will go through the following processes:
- PCB coat with solder paste
- PCB enter the automatic production line
- PCB enter multiple SMT mounting machines for different types of components
- Engineer roughly check and transfer to reflow oven
- Cooling PCBA and transfer to Automated optical inspection (AOI) machine for checking
If there is any problem identified by the AOI machine, such as missing components, incorrect component, short circuit, etc. Engineers will put a marking label on the board and transfer to technicians for simple repairing.
Step 5: Function Check
Please prepare the test jig for your own PCBA. Since the factory never know how your PCBA work and what kind of software / firmware working with it.
Test Jig is one of the most important instrument to ensure your PCBA with good quality. Besides, a good test jig design also save time in downloading firmware in each PCBA.