Hello,
On Package_SO,
There are several footprints which i think is same. Example :
SO-8_3.9x4.9mm_P1.27mm
SOIC-8_3.9x4.9mm_P1.27mm
SOP-8_3.9x4.9mm_P1.27mm
So what is the differences among those other that pad size?
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I think there is an unwritten rule. If you think that there is anything about IC packages which seems to be straightforward and easily understood, just wait. Some other vendor will come along and introduce something new to confuse everything.
I suspect there are no easy or shortcut answers to your question. Even the tolerances, plastic height (like SOT23 and TSOT); some vendor comes along to introduce a new variation that may be helpful or maybe just confuses things. That is caused partially by competition and partially by bad judgement.
One option for you would be to go back to vendor datasheets. Post some links to those if you want to have more discussion so we are all referring to the same thing. KiCad footprint libraries are another matter; they are probably OK but I do not use them much. I mostly make my own footprints.
When you take all of those varied dimensions and put them together, do you get a bunch of dimensions or a bunch of dementia?
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dementia I think. Many vendors have similar dimension, but different name on their datasheet.
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SOIC is a 150-mil body width and SOP is 209-mil. Both are 50-mil (0.127mm) lead pitch. You can make a footprint that handles both if you have such a need:
I seem to recall something about SOP having EIJ (japan) connection, but not positive. I have only run into a couple of SOP parts in the last few decades, from places like Rohm, iirc.
When a part is listed as SO, well who knows what that means – check the datasheet.
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In the footprints, the three of them are listed 3.9x4.9mm (there also other size). So I think body size is same.
I got a lot of value out of this chart recently.
I was trying to decide whether to substitute a SC-74-6 package or a TSOP6 package for a SOT666. Handy to know the difference is mostly letters and numbers rather that mils.
Despite that, you’ll often find each package has its own footprint. I did overlay a few that appear in the same column out of interest. Eg. here’s a TSOP-6 on top of a SC-74-6.
No doubt someone at some point had success with one or the other and is reluctant to change. Problem is that’s probably true for most combinations of package and footprint if they’re in the same column. Electronics manufacture can be pretty forgiving one day and take-no-prisoners brutal the next.
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Yeah Heath, part naming is out of control, and manufacturers are not always consistent. I embed the “aka” stuff into my footprint names so I can use one name I prefer and the footprint will work for all of them. True, every variant has its own preferred footprint, but the differences are generally subtle, and as you pointed out the reflow process is a lot more forgiving than some would insist.
So msop8 and msop10 have the same 3.0mm-wide body, but some manufactures call the msop8 a micro8, or uMAX8. Some even call it a tssop8 – but this is narrower than a real tssop8 (with a 4.4mm body), so I call it tssop8N to distinguish. Some manufactures call it vssop8, but there are two vssop8 sizes (see below):
The vssop8 in the 3mm body with the 0.65mm pitch (aka msop8), is common enough that I use that name sometimes, and msop8 sometimes, depending on the common usage for a part, but it is the same footprint. Then there is the smaller vssop8 which I call a vssop8N – it has a 2.3mm body and 0.5mm pitch, and is sometimes called a US8. The vssop10 is sometimes called a uMAX10 or msop10 or a tssop10, but is not the same as the 4.4mm body on a real tssop10:
I use sot23 and not the silly other name for these:
and I like sc70 for this family:
diodes and transistors:
Yeah, what a mess, and another good reason to build your own library and have consistency in your work. My hat is off to the kicad librarians, as they have quite a lot to sort out.
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Also, as BobZ pointed out, package heights vary, which you can usually just let the assembly house deal with. Some company cad policies will be more strict on a separate footprint for different height parts to distinguish. I have a lqfp family and a tqfp family – same footprint but separate name as these different-height parts are common so I distinguish with proper names. Find a naming convention that works for you (or is company-mandated).
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every time I see see all the different namings for SOIC footprints I am immediately reminded of this meme:
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when i’m having a difficult time figuring out the package/footprint i usually start with digikey. they seem to (at least try to) have a consistent package naming for parts. they’ll list MFG package (as “Supplier Device Package”) along with Package / Case so you can filter/sort by that package to find compatible parts. That can sometimes help if I have to make a new footprint, or want to see another “suggested footprint” for the same package. Mouser just seems to “punt” and only list the Supplier package name.
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Unfortunately there is no way around: always check the datasheet. I have my own library with my own naming convention and if it fits it’s all good, otherwise just another day with package making…
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