Regarding the point of "Via solder mask opening" and "Via solder mask tenting" (the usage distinction between PAD and VIA), many customers and design engineers often ask what this means when placing orders, which option should I choose for my file? Now the description of this problem is provide by China PCB manufacturer SYS Tech as follows:
We often encounter such problems, the design is seriously non-standard, and it is impossible to tell if it’s a pad or via usage. Sometimes the conductive hole is processed by the attribute of pad, and sometimes the key hole is processed by the attribute of via. The design of VIA attributes and PAD attributes is confusing, leading to wrong processing, which is also one of the problems that often appear in complaints. For circuit board production manufacturing plants, when processing CAM data, some engineers who deal with film, because the customer’s design documents are not standardized, and they will make the same mistakes as the customers’, help customers modify the documents, make the non-standard design right, and process the engineering data based on their own experience, which contributes to the non-standard design of customers. Hereby explain: The last time you did the right thing does not mean that your file is right! All engineers must pay attention to design standards and specifications! Strictly require all the film processing engineers to maintain the status quo of customer’s files as much as possible! Try to deal with the design specifications and standards as much as possible, not according to the so-called experience! Reflect the problems, so that you can be a reference for other design engineers, improve the design quality and reduce the occurrence of problems!
1. During the via outputting process, the design is not standard or you are not clear about the outputting Gerber setting rules, which causes problems. When you send a Gerber file, the PCB factory cannot tell which are vias and which are components holes. The only thing that can be identified is to process according to the file. If there is solder mask, there will be mask opening! A point in dispute: “I want via solder mask opening, but you have made via solder mask tenting now, which may cause short circuit.” “Then please check your file. The Gerber you have given is a film file. And the factory has no way to check whether holes in Gerber files are conductive holes or key holes. Please check the Gerber file to see if it has solder paste layer. If so, solder mask opening; If not, solder mask tenting.”
2. The pad and via are mixed together, causing problems
(1). If your file is outputted by PADs or PROTEL, when you send Gerber file to the factory and ask for via solder mask tenting, please carefully check whether your plug-in hole (pad) is also use via attribute, otherwise your plug-in hole will be covered with soldermask, which will result in non-soldering. A point in dispute: “the plug-in hole must be plated with tin on it. How do you make it tented?” “Please check the file when you say this. Is it pad design or via design in your file?”
(2). If your file outputted by PROTEL or PADs, when you send the file to the factory, order requirement is via solder mask tenting. Many customers use pad (plug-in holes) to indicate conductive holes, which will make your conductive holes opening. Maybe what you want is via solder mask tenting. At that time, the point in dispute will be: “what I want is conductive hole solder mask tenting. Why did you make it solder mask opening?” “Then please check the design in your file!”
Explain again as follows, if it’s via, deal with in via, if it’s pad, then just deal with in pad! Because no one will know which is the conductive hole or plug-in hole in your design, and via and pad is the only sign, please be clear!
3. How to design via solder mask tenting in PROTEL or pads! ——the following is the most standard way. If the design is standard, there will be no mistakes!
There is a tenting option in via attribute in PROTEL. If you check the option, it must be solder mask tenting. Then all you outputting are solder mask tenting. In pads, when you convert files, you need the method of via solder mask tenting: When outputting the solder mask, just click via under the solder mask top, which means that all are via solder mask opening. If you don’t click, that is, all are via solder mask tenting. To sum up as follows: if it’s pad, deal with in pad---this is the plug-in hole. As for via, you have two choices. If you provide the original file, PCB manufacturer will let you choose when you place the order. If you provide Gerber file, please check whether the Gerber file meets your requirements!