SOIC8 vs SO8 vs DSO8? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: May 21, 2023, 02:49:57 pm
content: Hi,These three docs say that SOIC8 , SO8 and DSO8 are all the same 6mm x 5mm size.But there is another wider format...usually known as "SO8" ...but the SO8 here is not it...which is it?SOIC8https://www.centralsemi.com/pdfs/case/soic-8pd.pdfSO8https://www.diodes.com/assets/Package-Files/SO-8.pdfDSO8https://www.infineon.com/cms/en/product/packages/PG-DSO/PG-DSO-8-16/

author: mariush
author_rank: Super Contributor
timestamp: May 21, 2023, 04:59:34 pm
content: You ask the weirdest questions ... Is it that hard to look at the recommended footprints and compare them?exsoic has 0.72mm x 1.78mm pads , 6.46mm - 2 x 1.78mm = 2.9 mm between pad rowsso-8 has 0.80mm x 1.5mm pads , 6.5mm - 2 x 1.5 = 3.5mm between pad rowsdso has 0.65mm x 1.45mm pads , 2 x 2.825 - 1.45 = 4.2mm between pad rows (edit: corrected, the pins are 0.41mm wide, pads are 0.65mm)up to you how much it matters, there's benefits and downsides (thicker pins do more current, more heat dissipation), wider chips may allow routing more traces under the chip, or larger pad with through hole vias for higher heat transfer to other side of pcb...

author: Faringdon
author_rank: Super Contributor
timestamp: May 21, 2023, 06:29:55 pm
content: Thanks, all the three from the top post would essentially fit the same SOIC8 pad.....(SOIC8 being a 6.2mm by 5mm "courtyard" part).There is a different version, that is significantly wider, that wouldnt fit it.But i cannot find itCan anyone find it?..I once layed out for it with a "normal" soic8 pad, and it wouldnt fit...it was way too wide.

author: Gyro
author_rank: Super Contributor
timestamp: May 21, 2023, 07:19:33 pm
content: Quote from: Faringdon on May 21, 2023, 06:29:55 pm1. Look at the package mechanical dimensions in the back of the datasheet for the part you intend to use. Use the footprint that matches that part.2. If there are multiple package variants, purchase the variant that matches your chosen footprint, it will have a different suffix. It is best to check the most commonly available variant to avoid delay or difficulty in sourcing.3. Repeat for the other parts you intend to use, chosing the appropriate footprint for each.P.S. If your footprint library does not contain an appropriate footprint, create one. Most companies create their own library of footprints, rather than relying on the ones that come with the CAD package.

author: Claude
author_rank: Newbie
timestamp: May 22, 2023, 05:10:16 pm
content: well... I never really considered that my first post on this forum would be to answer our, mhh, special guest, but here we go !!https://en.wikipedia.org/wiki/Small_outline_integrated_circuityou can see that there is a JEDEC and a EIAJ casing, the EIAJ is the special one (ATTINY13 for exemple can be delivered in both package).

author: Faringdon
author_rank: Super Contributor
timestamp: May 22, 2023, 06:03:07 pm
content: Thanks, from your kindly supplied wiki article, it looks like a "SOICx" is the ~6mm wide thing.The others, shoud lnot be called SOICs, and instead shoudl be called SOICx_N or SOICx_W (narrow and wide).But unfortunately, they all get called SOICsAn SO8 is always the ~6mm wide thing.So it looks like "SOIC" is the red alert package name....not to be used in any good BOM.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 24, 2023, 02:45:38 am
content: Quote from: Faringdon on May 22, 2023, 06:03:07 pmI'd say better stick to the exact package names for each chip and chip manufacturer, even if not exactly logical.While it means two different chips with the exact same package and footprint may have different package names in the BOM, and the same package name for different chips may refer to two different packages and footprints, it does mean anyone who checks the datasheets will get it right, every single time.And I say that is what matters (unless one is expected to work with a given footprint-and-package-name directory, of course).When you try to make the package names more descriptive, you make the verification harder, and any errors can be traced back to you even if not truly your fault, because the only reliable way to verify the package (or to map to a particular part) would be toask you.When you use the exact chip manufacturer package naming scheme, anyone checking the original datasheet, will always pick the correct one. (Except when the manufacturer does something as silly as change the naming scheme.) The onus of getting any replacement right, or picking the correct part out of a catalog, is on them, not you. You used the package name the manufacturer used, which is unambiquous and verifiable.While I am only a hobbyist myself, the same scheme applies to all scientific and technical discussions, specifically terms used. You can either define the term yourself (exact measurements and footprints for each package name in the BOM), or you can use the definitions most easily verified in that particular domain.Note, I did not say "the most popular definition", I said "most easily verified": that is the crucially important key difference here, too. Popularity is irrelevant wrt. the definition here; the verifiability and checking for correctness is the entire point.

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 24, 2023, 11:38:49 am
content: Just a an advice: try Google before asking such simple questions!

author: nctnico
author_rank: Super Contributor
timestamp: May 24, 2023, 06:20:52 pm
content: Quote from: DavidAlfa on May 24, 2023, 11:38:49 amYou can't 'thank' Google results

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 24, 2023, 06:27:49 pm
content: Quote from: nctnico on May 24, 2023, 06:20:52 pmNeither can google results make roll eyes or facepalms

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 25, 2023, 04:40:23 am
content: The question was not actually completely weird, there's a number of variations of so-called "SO8" packages, and unless this is an IC you already are familiar with, you better check in the datasheets for the exact packages, using the exact part reference. This has bitten a few people on occasion.