The PCB printed circuit board assembly process is the foundation of any electronic device such as computers, smartphones, gadgets and even cars. You must have seen a PCB, usually green, with copper wires connecting the various components of the board. But have you ever wondered how a PCB is assembled?
If you don't know the PCB's bill of materials (BOM), mount to the board. To provide 9 useful tips for a smooth, effective Bill PCB Get Assembly to the Board Bill of Materials (BOM). PCB manufacturing experience. You must understand the difference between these two processes to make your project a success.
PCB manufacturing refers to the process of producing bare boards after designers submit Gerber files to manufacturers. The first step is to add the circuit board substrate that makes up the insulating material. Copper is then added to the board, which is then etched away using chemicals, leaving only the necessary traces. The PCB manufacturing process also involves the application of drilling, electroplating, and solder mask. onic components are placed on the PCB to make it functional and ready for your project. Electrical components are placed on circuit boards using different techniques such as surface mount technology (SMT), pick and place machines, and hand soldering.
You need to decide which technology to use based on your needs and the electrical components you use. Sometimes you need to combine technologies like SMT and Through Hole Technology (THT) to assemble your PCB to get the desired result. SMT This will make it easy for the pick and place machine to pick and place components on the PCB easily, ensuring your PCB batch is successful.
Now you have a clear understanding of SMT). This will make it easy for a pick and place machine to easily place components onto a PCB (PCB assembly process. You need to find what you want from a PCB supplier. You don't want to risk assembling your PCB without knowing your needs. So pay attention to their preferences as well as the electronics needed for the project. Discuss the different techniques to find out which is suitable for assembly.
You also need to make sure your PCB supplier understands your needs and can meet your customer expectations.
You might also want to share a few words with your PCB assembler. Just as you get tips and advice from your PCB manufacturer to make your project a success, consulting your PCB assembler provides the same benefits.
This PCB Assembly can provide insightful tips for effective circuit board design, keeping you informed of current and improved technologies and materials. You can also learn about current PCB assembly trends to implement in your project.
1. Don’t make the mistake of avoiding DFM/DFA checks
Do you want your PCBs to be error free and operating at optimum capacity?
The answer is undoubtedly yes, because no one wants to produce a batch of defective PCBs. One way to ensure PCB design and functional accuracy is to run a DFM or DFA inspection. Most professional PCB assemblers offer DFM testing to verify and meet standard guidelines.
A DFM check ensures that you can identify errors in the initial stages of PCB design, so you can eliminate costly errors and delayed assembly. DFM is a comprehensive test that detects the failure footprint of electronic components.
By identifying problems before the assembly process, DFM allows you to correct errors before sending them off for assembly. The test also reveals any unnecessary, missed and potential problems. These include inaccurate spacing between components, footprint verification, component-to-component spacing, component-to-edge spacing, first pin indication, component polarity, cathode marking of diodes, and more.
Another mistake many designers make is to allocate very little space between components. DFM inspection is effective at finding such errors and helps create a batch of fully functional and good quality PCBs that will not fail or cause short circuits.
The goal of DFM is to reduce costs, speed up delivery, and improve product quality. DFM enables you to select the right components for your application and achieve the desired results, as even small mistakes can lead to significant losses affecting customer satisfaction. It also saves you the cost and time required for rework.
You may want to have DFM performed by experienced engineers who understand industry standards and have a keen eye for detail. In most cases, you don't need to worry about DFM, as your PCB assembler will probably handle it when you distribute your design.
2. Operation inspection of assembly materials
The PCB assembly process is all about placing different components on the board. , or you can get them yourself. No matter which option you choose, the quality of the components you will be using to assemble the PCB must be checked.
Professional PCB assemblers will have their quality control department responsible for evaluating incoming materials. Engineers will do a thorough inspection to make sure the components are working properly and can be used on your PCB without any failures.
Different aspects of quality control checks include date code verification, material handling testing and other tests to ensure components are in perfect working condition. Material inspection enables engineers to use only high-quality components, extending the shelf life of the PCB.
Some aspects of the incoming materials that the engineer checks are: quantity and model conforming to the BOM list, sample testing using multimeters, test stands, etc., deformation, oxidation or damage of complex components such as ICs
If you notice any discrepancies in incoming materials, you should immediately return them to your supplier so they can replace them in a timely manner. If you hire a professional PCB assembler, then you don't need to worry about replacement as it's the company's responsibility.
3. SMT solder paste screening
The PCB assembly process begins with applying solder paste to the bare board. If you've seen how to screen print a t-shirt, you have a pretty good idea of how the process works.
Instead of screen printing, place a thin stainless steel stencil on the PCB. The stencil covers the entire board, leaving only the pads for mounting Runze Wuzhou PCB, we have professionals and experts with the right skill set to meet your PCB needs. We provide services such as PCB manufacturing, PCB assembly (SMT equipment). The process is done using a machine, using mechanical clamps to hold the template on the board. An applicator then takes over and carefully dispenses the solder by moving it across the board. Solder is only suitable for open spaces where SMT components are mounted. If you are dealing with double-sided PCBs, you must repeat the process on the other side of the board.
The solder paste is a combination of powdered metal solder and flux which imparts its adhesive properties. It is usually grey and holds the different components in place by fusing them. The nature of the application and use of the PCB determines the composition of the solder paste. Typically, it contains varying percentages of copper, tin and silver.
Engineers inspect the board after the soldering process to ensure that solder is only applied in intended locations. They will also check the amount of solder on the pads to make sure enough has been used to mount the component.
4. PCB Assembly Process - Pick and Place Surface Mount Devices (SMD)
After placing the solder on the pads, it is now the turn to place the actual SMD components on the pads. SMDs do not have legs or leads like through-hole devices and can simply be soldered on the PCB. SMDs are the most common non-connector components in PCBs.
In the past, engineers would use tweezers to pick and place each component, which would take a long time and cause fatigue. Thanks to technology, we have powerful machines capable of "pick and place" SMDs on target pads. Machines typically use a vacuum to pick up components and align PCBs. It then places the SMD precisely at the selected coordinates of the PCB on the solder. You may need to perform several types of this step depending on the number of SMDs you plan to use.
For double-sided printed circuit boards, you need to "pick and place" one side at a time. The results are more accurate and consistent than manual labor and also suitable for mass production. Furthermore, the machine does not get tired or need to sleep and can work 24/7. Technology makes component placement fast and easy, all you need to do is program the machine correctly to pick and place SMDs.
5. PCB Assembly Process - Use Reflow Soldering to Protect SMD
The SMDs are now on the pads, the next step is to make sure they are seated properly. This means you have to heat and cure the solder in a process called reflow soldering. The PCBs are conveyed onto a conveyor belt and run through an industrial oven that heats the PCBs to a temperature of 480 degrees Fahrenheit. Therefore, as the PCB continues to move on the conveyor, the solder in the solder paste will melt.
Next, the PCB is processed to a series of cooler heaters so that the molten solder can cool and solidify properly. Now you have successfully secured the SMD to the pad permanently! An important consideration about this step is that SMDs are heated at a much higher temperature than manual and wave soldering. But don't worry, because today's SMDs are designed to withstand extreme reflow soldering temperatures.
Keep in mind that you cannot use this technique for many through-hole components due to the heat distribution involved. You have to use wave soldering or hand soldering to connect them. You must also stencil and reflow each side of the double-sided PCB separately. Start with the side with smaller and fewer components and work on the other side.
6. PCB Assembly Process - X-ray Inspection Time
X-ray inspection is performed after the reflow process to detect quality defects and other defects. It is also used for pre-flow inspection as well as bare boards during manufacturing. X-rays pass through the SMD's silicone and reflect off the metal in the solder, creating a digital image of the solder joint. You can analyze images with the help of image processing solutions.
High concentration features of PCBs appear as darker images, enabling you to use quantitative methods to measure the quality of solder joints. It can also be used to determine compliance with industry standards. X-ray inspection methods are mainly used for layered and complex PCBs because you can see through the layers. You can also use this technique to identify other major causes of defects, such as incorrect reflow profiles, insufficient solder paste volume, improper component placement, and more.
X-ray inspection is an important part of the PCB assembly process before final inspection. Eliminating this step can result in shorts, components falling off, and a shortened shelf life of the PCB.
7. PCB Assembly Process - Ends with Final Inspection
A reliable PCB assembler always wants to provide the highest quality workmanship so that customers never have a chance to complain! Many PCB companies conduct final inspections and X-ray inspections to ensure error free and functional PCBs. One of these tests includes automated optical inspection, which uses a camera to automatically scan your PCB to detect quality and catastrophic failures.
The technology uses cameras placed at different angles to find defects such as missing solder, inaccurate component placement, and solder shorts. Find all defects with a single technology through one interface. You can use this technology to process a large number of PCBs in a short time.
You can also consider manual inspection, which is still used in the PCB industry for low volume PCBs. In-person visual inspection is ideal for spotting defects, but takes time and puts pressure on engineers.
The final round of inspections may also include other tests such as In-Circuit Test (ICT) and Functional Circuit Test (FCT) to check the functionality of the electrical connections. Testing may cost extra, but make sure you can pinpoint the source of any errors.
PCB assembly is a multifaceted process that has become efficient with advances in technology and robotics. There is now less room for error, and most batches of PCBs are fully functional. Still, you need to keep the dos and don'ts we discuss in mind to ensure your PCB assembly process goes smoothly.
You need to establish clear communication with customers and PCB assemblers, make sure to run DFM inspections and check incoming materials. The use of the machine enables accurate component placement, while reflow soldering successfully secures the SMD to the PCB. Finally, take the inspection round and you're done!
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