Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Fine pitch & PCB finish

Dougs

#32776

Fine pitch & PCB finish | 21 February, 2005

Our machines can place components down to 16mil, I've never seen any finer pitch components in use, what pitch are they going down to now? 12mil??? What pitches have you been using? We are a contract manufacturer so customers sometimes supply free issue PWB's, these sometimes come in with fine pitch pad layouts and HASL finish, what pitch would you recommend you stop using the HASL finish and switch to one of the flat finishes.

thanks

Dougs

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#32780

Fine pitch & PCB finish | 21 February, 2005

Assembling boards with 12 pitch are very difficult to control.

We like flat surfaces on boards with components below 25 pitch.

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#32792

Fine pitch & PCB finish | 21 February, 2005

As davef states above, you would like to have flat surfaces below 25 mil. We are a contract manufacturer also and we've done thousands of 15 mil QFP's with HASL finish with no problems. Your success will depend on quality of PCB supplier providing the HASL finish along with stencil design. I didn't include equipment because we've processed 15 mil with DEK248 and DEK249 screen printers and placed them with "old" Philips CSM84VZ placement machine and now do it with Assembleon TopazX.

For proto's we've printed with the DEK's and had operators place them down with suction tool and checked alignment with a mantis scope prior to reflowing.

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Dougs

#32808

Fine pitch & PCB finish | 22 February, 2005

when you talk about stencil design, what would you recommend for aperture size on fine pitch if the customer insists on hasl finish on fine pitch devices? i usually use a 10% reduction on everything we have been using ( 16mil pitch and upwards and 0402 - 2512 chips ) BGA's i go 1:1 with pad size, always on a 6 mil thick stencil. i've been using this as i dont really get time to look into each pad layout and it seems to work ok.

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RDR

#32810

Fine pitch & PCB finish | 22 February, 2005

You may to reduce a little bit more with HASL. for .4mm pitch and such I would maybe go to a 5 mil with your standards.

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