altiumsolder-mask
I am new to PCB design, and especially on Altium. I am trying out it and have no clue of the best way to fix the following error:
I am trying to build a PCB for a Li-Ion charging circuit based on BQ24072. I have downloaded the symbol, footprint and 3D model from Texas Instrument's website. My manufacturer says they need a minimum of 0.08mm clearance between 2 pads mask. Here is the snapshot of 2D and 3D view of my PCB. What is the best way to overcome this issue?
It is a good idea to have a solder mask ridge between pads, as you say, to reduce the chance of short-circuits. It is not very important that the thermal pad on the PCB is exactly as large as the thermal pad on the component. With a smaller PCB pad you will most likely still get a good electrical connection and good enough heat transfer. (The exception would be when you are trying to use the component near to its maximum temperature and power.)
So, if you are not using the component near its thermal limits, reduce the size of the PCB thermal pad to allow a solder mask ridge around it.
Although not a direct answer to your question, another alternative is to use a smaller solder mask expansion. Perhaps 0.05mm would be enough depending on your manufacturing process.
Making the footprint is generally one of the fastest of all the things you need to do. There are Wizards in Altium that help you make IPC-compliant footprints quickly, and you can set the text height, silk screen line widths and so on to conform to your specific requirements and so your boards have a consistent appearance and set of manufacturing requirements.
Populating the data base with all the things that should be there (vendors, part numbers, alternates, prices, and so on) takes longer. Making a 3D body, if you need to, can take a lot longer depending on your proficiency with 3D parametric modelling software and whether you want to do a good job, a spectacularly good job, or something more slapdash. Here's a rendering of an LED body I did some time ago- the actual die dimensions and position is shown but I didn't bother with the bond wire. The typical library parts often have a crude 3D block or nothing at all.
You only make the part once and you can re-use it thereafter. It's a big hassle to add parts to inventory for the rest of the company, so maybe it will make you think twice about reuse.
Anyway, if you're at the beginner stage (we've all been there) and you just want to get going, use an 0805 resistor and it will be sub-optimal but usable (ignoring the 3D features and such like). You can edit it to show the polarity and save it in a library of your own. You can also download someone else's library that's been done more-or-less properly and (hopefully) learn from that and create your own as you gain experience. IIRC, the 0805 and other Imperial standard footprints may use the metric equivalent numbers (2012 for 0805) as part of their names.
Best Answer
All you need to do is change the soldermask expansion around the pads. You can open up the footprint in the library editor, select the pads, and in the Inspector change the expansion. Generally an expansion of 0.002 inches (0.051 millimeters) is sufficient, but if you have space you could increase that a bit. The required distance between soldermask openings will depend on your board supplier and their requirements.