What Are the Preparations before SMT PCB Assembly?

What separates surface mount from through-hole technology is that there is no need to drill holes in the circuit board to connect the tracks and the components. Establishing relationships through leads. The ingredients are in direct touch with the PADs of the circuit board And add solder paste to PAD with the help of stencil solder. There is also a pick and place machine responsible for placing the components on the solder paste set initially above the PAD. After setting these components, they have to be placed in a reflow oven or introduced in a vapor phase to be soldered permanently in the surface mount PCB assembly.

Goto Hayawin to know more.

If you are searching for more information about surface mount technology in PCB manufacturing, please check and read the content below for more professional knowledge.

If you want to order PCB product, please check and custom your order online.

What Are the Preparations before SMT PCB Assembly?

A few preparatory steps have to happen before real PCBA process even begins. This helps PCB manufacturers assess the functionality of a PCB design, and primarily includes a DFM check.

Most companies specializing in PCB assembly need the design file of the PCB to start out, along with any other design notes and specific requirements. This is so the PCB assembly company can check the PCB file for any issues that may affect the PCB's functionality or manufacturability. This is a design for manufacturability check, or DFM check, for short.

The DFM check looks at all the design specifications of a PCB. Specifically, this check looks for any missing, redundant or potentially problematic features. Any of these issues may severely and negatively influence the functionality of the final project. For example, one common PCB design flaw is leaving too little spacing between PCB components. This can result in shorts and other malfunctions.

What is SMT and its advantages?

Surface Mount Technology is a newer way of arranging components on printed circuit boards. For many years prior, electricians and engineers would use leads to fit circuit board components through holes. Careful preparation was necessary to ensure that all leads were formed in the right way to fit on various types of boards.

SMT assembly is a more efficient process where components are soldered directly onto the board. By eliminating the need for passing leads through PCBs, the process has become faster, more efficient, and cost-effective. SMT assembly also saves space, allowing more components to be housed on a smaller board. This is why many modern devices are smaller but pack lots of features.

SMT is a highly intricate process where each component is strategically positioned and mounted onto electrical boards for optimal functionality. This is one of the reasons why SMT and SMD overlap. Having an effective electrical device requires a combination of proper component selection and mounting strategies. During SMT, calculated amounts of solder paste are applied onto the board before a machine carefully mounts each component.

How to choose PCB SMT factory?

Choose the equipment

This is the first and most important thing to do when choosing a production facility. The factory must be located in an area with excellent communication systems. It is suggested to ask the factory owner why they chose that area. Is it close to the railway or highway? Is it near the airport? These are all good questions to ask when choosing a factory. If you are going to have your own transportation, it becomes less important if it is close to transportation lines, but if you are going to use public transport, this will become a priority.

Industry experience

Many factories will claim that they have been in the industry for a very long time, but this is not always true. If you are not careful, you may be cheated. Therefore, it is suggested that you should check the company&#;s records and find out how long they have been in business and whether or not they have a good reputation.

The following are some of the methods to check if a factory has a good reputation. First, it is suggested to ask around about this factory by talking with other suppliers or customers who may know about them. Second, if possible, you should go to the factory and talk with its employees; their attitude towards you will show their reputation. Third, you can visit some of their customers and ask them what they think of the factory; their answers will also help your decision.

Delivery Ability

The next important thing to do when choosing a factory is checking their delivery ability. If a factory cannot deliver on time, it may render your project useless. Therefore, it is very important to check the factory&#;s delivery ability before making a purchase.

How to decide which technology is best for design?

Manufacturing tests like PCB functional test the best time to decide between an SMT or PTH part is when you are choosing the components that you will use in your schematic. By incorporating these parts early in the design, you will make sure that the PCB Layout is created with the correct component package footprints. Here are some questions to consider when making your decision:

·Use: Will this component get &#;touched&#; much or be subjected to other stress?

·Power: Will this component be conducting a lot of power and heat?

·Performance: Which package style will give your circuit the best performance?

·Price: Is there a price benefit by choosing one package style over the other?

      `  Availability: How quickly will the part be available for prototypes?

Last time Angell and Lesley elaborated the most basic and frequently asked questions about PCB Assembly. And today we&#;ll focus on some details.

This time we invited Aimee, another our senior customer service staff, to our Channel. Hope her professional answer can help you know our PCB Assembly service better.

Q1&#;Aimee, working in a PCB Prototype company, we&#;ll inevitably meet some urgent orders. For PCB order, our customers can choose extra urgent service to meet their needs. Then do we also offer expedited service for PCB Assembly?

Aimee: Sure, we can expedite assembly service when all components are ready. For components procurement, it normally takes a certain time and process. so The room to speed up this process is little.

Q2: When placing an order, some makers may have ideas like: I want blank PCBs and components separately for 5pcs and another 5pcs assembly completed. So can it be achieved?

Aimee: There is no problem to choose different quantity for PCBs and assembled boards, but the PCB quantity should be larger than assembled boards. The number of PCB and the number of PCBA are not necessarily the same, but the MOQ for PCB is 5 and no MOQ for assembled boards.

Q3: For PCB or PCBA service, we provide 3 kinds of flexible options for part supply. They&#;re PCBWay supply parts; Customer supply parts; and You supply some parts we do the rest. Then what issues are important for customer-supplied parts?

If you want to learn more, please visit our website Assembly Smt.

Aimee: There are 3 aspects.The 1st one is Markings. Each packaging should include part number, package, value information same as the ones in BOM. It&#;s better to add designators to each packaging if you can. If there is anything different from information in BOM, please remember to contact us to correct BOM in advance.

The 2nd one is Parts Overages. You know, we must prepare some extra components to prevent the unnecessary part damage or loss. For Resistors, Capacitors and Diodes with the following packages - (, , , , SOT, SOD, MELF ), the required minimum quantity is 50 pieces including 30 pieces extra over assemble quantity. For example, if the assemble quantity is 40 pieces, 40 plus 30, then we will need 70 pieces in total. For Resistors, Capacitors, Diodes with other types of packages - (, , mini Melf, miniature packages) , the required minimum quantity will be 100 pieces including 50 pieces extra over assembly quantity. For example, if the assemble quantity is 80 pieces, then we will need 130 pieces. As a means of improving efficiency and security, a small number of excess is also requested for expensive parts such as IC, BGA, QFP, Connectors, etc. And the quantity can be 1-5 pieces based on the total quantity of assemblies. 

The last one is the Packaging of Parts. Based on our experience, here&#;s some advice. SMT parts that are not supplied on reels should be on one continuous strip of tape. If there&#;s a need to assemble the same SMT part on different boards, please keep them in the continuous strip of tape or on the reels. Do not cut them into strips. Furthermore, Components on the tube or tray are good for assembly as well.

Q4: Aimee, it&#;s a common situation that sometimes we cannot find some components due to uncontrollable factors. Under this circumstance, will we recommend substitutes in the quotation?

Aimee: Sure, it&#;s a part of our job. If our customers accept to use substitutes for assembly, then you can list a column of substitutes (Yes or No) in BOM. At the same time, the detailed specification of components can help a lot. Don&#;t forget to write it down in the BOM file.

Q5: Aimee, what will happen when the Infos in Centroid file and BOM file are different? I know sometimes the parts are not soldered just because the BOM file doesn&#;t cover some info which is on the relative Centroid file.

Aimee: Normally we purchase and solder the parts just based on your BOM file. And centroid file is just used to confirm the position of each parts, so it is important to make sure that BOM list includes all the parts you need.

Q6: Then after assembly, are there any tests to make sure everything works well?

Aimee: Of course yes. Normally we will do AOI test after assembly.

As for IC or BGA area, we can do X-ray tests if there&#;s a request from our customers. And the test result will be provided to them for review. What&#;s more, we suggest testing the LEDs after assembly when your components include some. Cause if not, generally the result will contain around 2% failure.

Q7: What documents are needed for testing service?

Aimee: There are 3 different situations.

For LED testing, we&#;ll require them to send us the testing procedures with pictures showed.

For the function test, the test methods are needed, including the test steps and pictures. Moreover, it will be better if there&#;s any test video for reference. Oh, our assembly factory only has the conventional universal meter, so please send us the specific test tools when it&#;s necessary to test your project. 

For both LED testing and function testing, the test fee will be confirmed and charged after testing, which is calculated according to the time used.

Q8: Aimee, can we program for our customers when the assembly and test is completed&#;

Aimee: Yes, we can program some parts. If you have this need, just let us know which parts in the BOM you need us to do programming, and send us the relevant boot loader files, which usually is .hex file. Then our engineer will check whether we can do it and quote for the extra programming fee.

Q9: Can you explain deeper about the IC programming?

Aimee: Sure, IC programming will be performed before the chips are mounted on the board. You can contact with your own customer service for details. Besides, we also have a qualified programming management system. We understand the importance of Intellectual Property (IP). We will sign a Non-Disclosure Agreement (NDA) document on the request of the customer in order to protect IP rights.

Q10: Quite professional. The next question, will we send pictures to our customers for review?

Aimee: Another good question. During the manufacturing process, PCBWay will send sample pictures to you to confirm everything is correct. But please note that we just put the PTH parts on the position and the PTH parts are not soldered yet. If customers find any position or direction problems, we can make easy correction .After customers confirm the sample picture, we will finish the soldering for PTH parts.

Q11: Once the sample picture is confirmed, how long will it take to ship out the assembled PCBs?

Aimee: It depends. Because there&#;s a difference between orders, like assembly quantity, PTH components quantity, and whether there are special procedures or not. But I can tell an approximate duration. If it&#;s a prototype order, it usually takes 3 working days; For small and medium quantity orders, it usually takes 3 working days; And if there is a special requirement like con-formal coating and function testing, we need to check the complexity to confirm the final lead time.

Q12: Will you ship the stencil back to our customers when the assembly is finished?

Aimee: Usually we will not ship the stencil back to you,it will be stored in our warehouse for the use of repeat order in the future. If you really need it, the SMD-stencil can be shipped to you too,while you have to pay for the extra shipping cost. The stencil with framework is much heavier than PCB. When shipped, it adds a lot of weight.

Q13: After receiving the boards, what to do if there are any defects?

Aimee: You're always encouraged to contact our after-sales team at any time and use the pictures or videos to show the issue .

And it'll be better that you can analyse the reason to help us to solve problem soon.

If the problem is related to components, apart from the part NO., please tell the relevant designators in the bom too.

BTW, please do not repair the defective boards by yourself before we confirm the real reason .

If you have any questions about your orders, just leave a comment below or send a message to .

Project Planning&#;Simon

For more information, please visit Automatic Labeling System.