Summarizing the experience of PCB packaging

qwqwqw2088

Summarizing the experience of PCB packaging [Copy link]

 

      I believe that everyone who has done hardware design has experienced making component or module packages by themselves, but it is not an easy task to make a good package. I believe that everyone has had such experiences: (1) The spacing between the package pins is too large or too small, making it impossible to assemble; (2) The package is drawn upside down, causing the component or module to be installed on the back to correspond to the pins on the schematic; (3) The large and small pins of the package are reversed, causing the component to be turned upside down; (4) The package is inconsistent with the purchased component or module, making it impossible to assemble; (5) The package frame is too large or too small, which makes people feel uncomfortable. (6) The package frame is misaligned with the actual situation, especially some mounting holes are not placed in the right position, making it impossible to screw in. I believe that many people have encountered such situations. I hope that I will not make such mistakes again in the future. After drawing the schematic, it is time to assign packages to the components. It is recommended to use the packages in the system package library or the company package library, because these packages have been verified by predecessors. If you can avoid making the package yourself, don't make it yourself. But many times we still have to make the package ourselves, or what should I pay attention to when making the package? First of all, we must have the package size of the component or module at hand. This is generally explained in the datasheet. Some components have recommended packages in the datasheet. This is that we should design the package according to the recommendations in the datasheet; If the datasheet only gives the outer dimensions, then when making the package, it should be 0.5mm-1.0mm larger than the outer dimensions. If space allows, it is recommended to add an outline or outer frame to the component or module when making the package; if space really does not allow, you can choose to add an outline or outer frame to only some components. There are also some international specifications for the packaging of components. You can refer to IPC-SM-782A, IPC-7351 and other related materials. After you have drawn a package, please check the following questions. If you have answered all the questions below, then there should be no problem with the package you have built! (1) Is the pin spacing correct? If the answer is no, you may not be able to solder it! (2) Is the pad design reasonable? Pads that are too large or too small are not conducive to soldering! (3) Did you design the package from the perspective of Top View? It is best to design the package from the perspective of Top View. Top View is the angle when you look at the pins of the component with their backs to you. If the package you designed is not designed from the perspective of Top View, after the board is completed, you may have to solder the component with its four pins facing up (SMD components can only be soldered with their four pins facing up) or install it on the back of the board (PTH components should be soldered on the back). (4) Are the relative positions of Pin 1 and Pin N correct? If they are wrong, you may need to install the components in reverse, and you may have to make flying wires or even scrap the board. (5) If the package requires mounting holes, are the relative positions of the mounting holes correct? If the relative positions are incorrect, it may be impossible to fix it, especially for some boards with modules. Since there are mounting holes on the module, there must be mounting holes on the board as well. The relative positions of the two are different. After the board is built, the two cannot be well connected. For more complicated modules, it is recommended to let ME make the module frame and the mounting hole positions before designing the module package. (6) Have you marked Pin 1? This will facilitate later assembly and debugging. (7) Have you designed an outline or frame for the component or module? This will facilitate later assembly and debugging. (8) For ICs with many and densely packed pins, have you marked the 5X and 10X pins? This will facilitate later debugging. (9) Are the sizes of the various marks and outlines you designed reasonable? If not, the designed board may be a pity.

led2015

The worst thing about encapsulation is that you think you understand it, but it doesn’t work in practice

bioger

Packaging is a meticulous job. It is good in terms of technology, but also requires a certain amount of experience. Now I see that many device packages are not drawn in a very standard way.

不足论

I want to learn to paint this, are you hiring apprentices?

qwqwqw2088

Busuolun published on 2018-1-30 09:33 I want to learn to draw this, are you hiring apprentices?

You can post for help at any time during the drawing process, and I will do my best to help

star_66666

Learn

rizhi

Very helpful experience

我达达的马蹄

Study

shijizai

Thanks for sharing, thumbs up

shijizai

Where should I find the dimensions when drawing a package? For example, I want to draw a 2220 package capacitor, but I don't know the specific dimensions of the capacitor and the size of the pad. Should I directly search on Baidu? But I don't know if the results from Baidu are correct. The dimensions above also have a range. For the range of dimensions, such as plus or minus 0.6, should I calculate by plus 0.6, minus 0.6, or the size without plus or minus?

qwqwqw2088

Shijizai posted on 2019-4-21 11:32 Where should I find the size of the package when drawing it? For example, I want to draw a capacitor with a 2220 package, but I don’t know the specific size of the capacitor and the size of the pad...

The pads of the capacitors with a 2220 package from each manufacturer are slightly different, and even vary a lot. Draw the package based on the capacitor you want to choose. That is, select the sample in advance, or ask the manufacturer to provide the pad package size. If it is manual welding or machine patch welding, the pad package has different designs, and the manual welding pad can be appropriately enlarged.

qwqwqw2088

If you search Baidu for package dimensions, use pad graphic dimension data, or download packages from other places, they must match the package shape, solder terminals, pins and other dimensions related to soldering of the components you choose. Otherwise, there will be more soldering problems and low-level errors. In addition, the soldering reliability of surface mount components mainly depends on the length of the pad rather than the width.

shijizai

qwqwqw2088 posted on 2019-4-21 12:04 If you go to Baidu to find the package size, use the pad graphic size information, or download the package from other places, it must be consistent with the package of the component you choose...

Well, thank you very much

shijizai

qwqwqw2088 posted on 2019-4-21 12:01 The pads of the capacitors in the 2220 package of each manufacturer are slightly different, and even very different. Draw the package according to the capacitor you want to choose. That is, select the sample in advance...

I have learned a lot, thank you very much

coldmaximum

I learned it, thank you sir.