Well, that's close enough for govmint werk, LOL!





-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Showers

Sent: Thursday, September 06, 2018 11:34 AM

To: [log in to unmask]

Subject: Re: [TN] PTH Fine-Pitch Definition



Richard, I am somewhat in your boat, but the definition I was always presented with is .65mm (25.6mil) and smaller is classified as fine pitch.  This is the definition used by Topline for their dummy parts.  I have also seen this number floated about in several papers and equipment manuals.



For lack of clarity, I would propose this as a good guideline based on IPC inspection criteria.

That is, once we are at 0.65mm (and lower), the lead width itself, by necessity, reduces to 10 mils (0.25mm) give or take.

At 10 mil (0.25mm) lead width, Table 1-2 of IPC-A-610 jumps the required inspection magnification from (7.5X to 10X) up to 20X for inspection.