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15.7 mil QFP

Steve Schrader

#24636

15.7 mil QFP | 29 May, 2003

What is the general feeling in the industry on the use of 15.7 mil QFP's? Are most people shying away from them in favor of BGA or do most people consider 15.7 mil to be "standard" technology these days? What special considerations are involved?

Steve

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#24637

15.7 mil QFP | 29 May, 2003

I do not recommend using a HASL finish, you will have a very tough time printing repeatably.

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RDR

#24654

15.7 mil QFP | 30 May, 2003

We place a large amount of .4mm (what is that in microns?)QFPs every day. I would much prefer a BGA package. Reasons are 1. Pitch is greater which provides a larger process window 2. Alignment is easier because you don't need vision for BGA if you get the part on the pads 50% they will come out fine. Not using vision speeds up our process (Our equipment has fixed vision for leaded finer pitch devices and a laser scanner for non critical placement parts 50 mil pitch, discreetes etc..) 3. PCB finish is not as critical. We have to use HASL finish on these assemblies that we are producing and fiducial and pad finsh quality is not what I would call optimum. This affects solder volume and placement accuracy. 4. Much less real estate than QFP with same pinout.

If you are going to use .4mm pitch make sure that you use a flat finish like ENIG, or an OSP.

P.S. Lets not even talk about the .3mm pitch.

Russ

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Jon Fox

#24655

15.7 mil QFP | 30 May, 2003

Conversion refresher:

1 inch = 25.4 mm 1 inch = 25,400 microns

10 microns = 0.3937 mils 10 microns = 0.010 mm

so 0.4mm = 400 microns

and for s/n/g:

1mm = 3.240783e-20 parsecs (pc)

Have some fun with that one!

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#24664

15.7 mil QFP | 2 June, 2003

Hi Steve, Why are you so concerned about QFP(0.4) or BGA? If your equipment can manage, what's the difference? If you are designer do it better and use the cheaper or smaller package(you decide). If not use machine with vision recognition and your problem is solved. Good luck!

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#24668

15.7 mil QFP | 2 June, 2003

yo Evt, ".., what's the difference?". Answer: Huuuge!! between running 0.4mm pitch QFP and a BGA of same I/O, in terms of handling, storage, feeding (trays), p&p, inspection, test, rework, etc.......

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mk

#24676

15.7 mil QFP | 3 June, 2003

Orrrrrr, you could eliminate the printing, shorting, and special surface finishes by bringing the boards in with the paste already on them. There is a process that is a much more forgiving method for applying paste called solid solder deposit. Check out http://www.sipad.com/SSi_0157pitch.htm

BGA's, QFP's, does not matter.

Good luck. mk

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#24695

15.7 mil QFP | 4 June, 2003

Hi Pete I agree with all that. But his question was "Are most people shying away from them in favor of BGA or do most people consider 15.7 mil to be "standard" technology these days?" So, the truth is people use both.QFP has advantages and disadvantages and the poisnt is WHAT needs Steve has?(design or manifacture?) Thanks for correction you made me, but my point of view was different.

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