Printout of ic pads in physical size - Page 1
Forum section: electronics / general

author: exodia
author_rank: Contributor
timestamp: October 18, 2010, 06:25:19 am
content: Hello fellow matesI have searched the web but i haven't found a single piece of paper to print about the physical size of IC pads. The more experienced users are all familiar with the real dimensions of the Ic's but for new comers this is a pain in the butt. So have anyone found a list of real ic dimensions?

author: Bored@Work
author_rank: Super Contributor
timestamp: October 18, 2010, 06:39:16 am
content: Every self-respecting datasheet contains the information for the particular IC, typically at the end of the datasheet. Also self-respecting semiconductor manufacturers publish their case types and dimensions in addition in application notes, engineering notes, manuals, or the like. These days everything is on their web sites.

author: exodia
author_rank: Contributor
timestamp: October 18, 2010, 07:34:14 am
content: What i mean is a physical size printout of the Ic's size so i can have a reference size before i put a particular IC in PCB. Like an A4 paper with the IC pads. Take a look at the picture i include

author: joelby
author_rank: Frequent Contributor
timestamp: October 18, 2010, 12:53:12 pm
content: If you design the component layout in your EDA software to the measurements given on the datasheet and print it at 100%, it should be the correct size. Repeat for all the kinds of package you require. If you have the parts on hand, sit them on top of the printout and make sure they line up before having boards made. In practice there are so many different patterns that it's probably not worth and not possible to compile a reference that has them all. A good PCB library (such as Sparkfun's Eagle library) should have verified versions of all standard footprints, but it's quite easy to create and check them yourself with most packages.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 18, 2010, 01:58:47 pm
content: Quote from: exodia on October 18, 2010, 07:34:14 amif you got the chip, then you can start measuring and draw according to your measurement.

author: migsantiago
author_rank: Frequent Contributor
timestamp: October 18, 2010, 02:25:40 pm
content: Quote from: exodia on October 18, 2010, 06:25:19 amIn my experience I've seen that robust PCBs should have these dimensions:Diameter85 mils for little pins120 mils for big pins (diodes and power stuff)Drill diameter40 mils and 62 mils according to the pad diameterWhen you send your board for fabrication, the PCB fabricants will be happy to know that the drills you want to use are all of the same size. They won't be changing the driller so often.And every IC in the market has its own datasheet. All datasheets must include chip dimensions and recommended PCB routing.

author: DJPhil
author_rank: Frequent Contributor
timestamp: October 18, 2010, 03:24:14 pm
content: If you're just looking for a rough idea, checkFairchild's package data section.Click on something that's close, as an example say SOIC.Click on the pin count, say SOIC 8-Lead. There can be more than one, so make sure it matches what you're using.Click on thedevice dimensions pdf.The footprint data is included. Many manufacturers include this with the physical measurements of the IC near the end of their datasheets.Hope that helps.

author: Bored@Work
author_rank: Super Contributor
timestamp: October 18, 2010, 03:36:55 pm
content: Quote from: exodia on October 18, 2010, 07:34:14 amAnd what is wrong with the dimensions and drawings in the datasheets?

author: exodia
author_rank: Contributor
timestamp: October 27, 2010, 05:39:48 pm
content: DJphil and joelby u helped with the fairchild and sparkfun library i'll check themThank you all

author: allanw
author_rank: Frequent Contributor
timestamp: October 27, 2010, 07:36:38 pm
content: Most datasheets don't tell you the land pattern you need for the pads though, like how much extra horizontal space you need for each pin.There's some software like LPC viewer or something that lets you enter in the IC dimensions and it'll give you the right footprint.

author: Zad
author_rank: Super Contributor
timestamp: October 27, 2010, 10:10:50 pm
content: A certain popular Australian PCB CAD suite comes with a really nice 'wizard' that takes your parameters and generates the pads, masks, keep-outs etc. Very nice