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SMT electronics assembly manufacturing forum.


Re: 8 mil placement, part Deaux!!

tim scully

#14337

8 mil placement, part Deaux!! | 11 September, 1998

Thanks to all Earl, Mathew and David for the SMT info. I have one more question. Does anybody have a chart listing the standard, industrial spacings? Perhaps listing in each unit, say XX mils = XX Pitch. Or XX mils = XXmm or something of that nature? Are there standard lead spacings? Thanks again for all of your help. I'm learning more each day. Someday I'll be an expert on SMT placement, won't my friends be impressed! -Tim

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Earl Moon

#14340

Re: 8 mil placement, part Deaux!! | 11 September, 1998

| Thanks to all Earl, Mathew and David for the SMT info. I have one more question. Does anybody have a chart listing the standard, industrial spacings? Perhaps listing in each unit, say XX mils = XX Pitch. Or XX mils = XXmm or something of that nature? Are there standard lead spacings? | Thanks again for all of your help. I'm learning more each day. Someday I'll be an expert on SMT placement, won't my friends be impressed! | -Tim My hat's off to you being only a "salesman." It's refreshing seeing one of you guys going the extra mile to learn technology to better serve customers and, of course, your paycheck - which you will earn on this project. The answer to standard pitch or spacing is but a vapor floating on the breeze. Device suppliers take every opportunity to push the envelop way out of shape. This is both a service and one not so kindly named. As we discussed, the world and everything in it is shrinking. If you want to component type and spacing availability, check JDEC standards and all the suppliers in the known universe. If you want to know what's in the wind, check your barometer. Seriously, the real world knows current "practical" boundaries at the 20 mil pitch level for effective, efficient QFP, as an example, placement. Stretching that, we go to 12 mils and the 0402 chip device world. Stretching that finds us in the yaya land of 0201's. Then we go to BGA and uBGA to gain the space not afforded by using QFP's (you can place them in closer proximity and run multiple traces under them on different layers). uBGA designs are stretching it. I am told by Jason's father that in the Asian technical community, BGA's are not as popular as are flip chip designs. And on it goes - what is impossible today will only be difficult, for a short time, tomorrow. Earl Moon

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Dave F

#14338

Re: 8 mil placement, part Deaux!! | 11 September, 1998

| Thanks to all Earl, Mathew and David for the SMT info. I have one more question. Does anybody have a chart listing the standard, industrial spacings? Perhaps listing in each unit, say XX mils = XX Pitch. Or XX mils = XXmm or something of that nature? Are there standard lead spacings? | Thanks again for all of your help. I'm learning more each day. Someday I'll be an expert on SMT placement, won't my friends be impressed! | -Tim Tim: As Mr. Moon said, there is a ton of different pitches. And if you were designing or assembling a board, you should know the details of that component. There are no generalizations or assumptions when it comes to getting components attached to a board. None the less, there are several component pitches that are fairly standard. They are extremely standard from a sales person stand point. So the next time yer burnin' a brat with an Ol' Mil' ya can wow 'em this one. 1.27 mm -> 0.050" -> 50 mil -> 50 pitch 0.80 mm -> 0.032" -> 32 mil -> 32 pitch 0.64 mm -> 0.025" -> 25 mil -> 25 pitch 0.50 mm -> 0.020" -> 20 mil -> 20 pitch 0.40 mm -> 0.016" -> 16 mil -> 16 pitch 0.20 mm -> 0.012" -> 12 mil -> 12 pitch Dave F

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Dave F

#14339

Re: 8 mil placement, part Deaux!! / My Mistake - Sorry | 14 September, 1998

| | Thanks to all Earl, Mathew and David for the SMT info. I have one more question. Does anybody have a chart listing the standard, industrial spacings? Perhaps listing in each unit, say XX mils = XX Pitch. Or XX mils = XXmm or something of that nature? Are there standard lead spacings? | | Thanks again for all of your help. I'm learning more each day. Someday I'll be an expert on SMT placement, won't my friends be impressed! | | -Tim | Tim: As Mr. Moon said, there is a ton of different pitches. And if you were designing or assembling a board, you should know the details of that component. There are no generalizations or assumptions when it comes to getting components attached to a board. | None the less, there are several component pitches that are fairly standard. They are extremely standard from a sales person stand point. So the next time yer burnin' a brat with an Ol' Mil' ya can wow 'em this one. | 1.27 mm -> 0.050" -> 50 mil -> 50 pitch | 0.80 mm -> 0.032" -> 32 mil -> 32 pitch | 0.64 mm -> 0.025" -> 25 mil -> 25 pitch | 0.50 mm -> 0.020" -> 20 mil -> 20 pitch | 0.40 mm -> 0.016" -> 16 mil -> 16 pitch | 0.20 mm -> 0.012" -> 12 mil -> 12 pitch | Dave F You know I did something that design engineers like to do to drive process types nutzz!! I used a short-hand conversion between millimeters and inches of 40. It's a handy number to use to get you in the ball park. But truely 39.4 is a better number to use. 39.3701 is better and .... These conversions are soft metic conversions. Design engineers can select hard metric in most CAD programs. Soft metric conversions, depending on the precision selected, can result in "process errors" that are tough to resolve, as component pitch becomes finer. This happens because there can be a mismatch between the metric measurement of a component and the soft metric conversion to develop pads. Metric -> soft -> firmer -> firmer yet 1.27 mm -> 0.050" -> 0.0500" -> 0.05000027" 0.80 mm -> 0.032" -> 0.0315" -> 0.03149608" 0.64 mm -> 0.025" -> 0.0252" -> 0.02519686" 0.50 mm -> 0.020" -> 0.0197" -> 0.01968505" 0.40 mm -> 0.016" -> 0.0158" -> 0.01574804" 0.30 mm -> 0.012" -> 0.0118" -> 0.01181103" 0.20 mm -> 0.008" -> 0.0079" -> 0.00787402" The other mistake I made was, labeling the conversion for 0.30 mm as "0.20 mm." Sorry. ;-) Dave F

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