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Can you wave solder this part

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All, Is it possible to wave solder the following componen... - Aug 22, 2006 by

aj

#43472

Can you wave solder this part | 22 August, 2006

All,

Is it possible to wave solder the following component?

http://www.national.com/packaging/folders/src14a.html

aj...

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#43474

Can you wave solder this part | 22 August, 2006

Without having tried it, I'll be the first to say I don't know how you could, and I would have no trouble at all telling my management absolutely not.

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Rob

#43475

Can you wave solder this part | 22 August, 2006

No, not by us mere mortals but where there WML there's hope.

I'm not convinced the package would like around 260C either.

Disclaimer:

Please note I am just a simple engineer and was not privileged enough to attend Soltec University, instead having to settle for four years at a quaint, backwood ye olde English establishment.

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#43476

Can you wave solder this part | 22 August, 2006

Some university you went to, Rob. You can't even spell "old". ;)

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RDR

#43477

Can you wave solder this part | 22 August, 2006

Cannot be done, no way to solder the heat pad underneath center.

P.S. Rob also spells color wrong!!! must have been a real bad school!! How does the wave master do it?

Russ

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Chunks

#43480

Can you wave solder this part | 22 August, 2006

Russ is right. The pad in the middle needs to be soldered as well. Also, the ends of leads exposed are not plated as well, so you will never get a toe fillet. Drives our IPC experts nutty, or should I spell it "knutee"? I don�t know, I went to a hick college in Indiana that stinks. People keep calling me a PU graduate! OK, I�m sorry. To punish myself I�ll pay to go see Snakes On A Plane.

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aj

#43492

Can you wave solder this part | 22 August, 2006

I did not think it was possible but I just thought I would ask and save me some time.

Cheers,

aj...

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#43500

Can you wave solder this part | 22 August, 2006

National says: [ http://www.national.com/packaging/llp/faq.html#faq_manu ] Manufacturing FAQ's Are there any precautions that need to be taken with the LLP package? It is critical to follow National�s guidelines for successful surface mount process Like BGA�s and other land grid array packages the solder joints can not be viewed from the top without X-ray

What pick and place equipment can be used for LLP? a) The standard pick and place equipment that can handle BGAs and QFPs with 0.5mm pitch can handle LLP. The LLP has been picked and placed successfully using Fuji, Panasonic & Quad, Siemens, ESEC, Sanyo, Amistar, and Universal equipment.

How do customers determine if the solder joint is reliable after re-flow? a) Using X-ray inspection of the solder joint after re-flow is the recommended method.

What is the recommended solder reflow profile? a) The recommended soldering profile is included in National�s LLP package application notes, AN-1187, and meets IPC-9502.

Can the LLP package be reworked after soldering on the PCB? a) Yes, commercially available rework equipment can be used to rework LLP .

Is LLP shipped in Tape & Reel? a) Yes. LLP is shipped in tape and reel using industry standard guidelines (ref. EIA-481-1).

Can this package be hand soldered? a) No. The contacts are on the bottom of the package and no contacts on the side.

What is the reliability of the package after rework? a) With proper rework the reliability is the same as a new part

Can this package go through wave solder? a) No. Due to specific design of LLP with contacts on the bottom wave soldering is not possible.

Is National available to assist in manufacturing? a) Yes. Please contact the LLP team in the Package Technology Group through your local National Semiconductor sales engineer.

Are voids acceptable in the solder between the PCB land and the thermal pad of the package after surface mount? a) National has done extensive modeling and studies on the impact of voids and the results are summarized in AN-1187.

What is the standoff for this package after surface mount? a) Typically about 2 mils

Can a "no" clean solder paste be used? a) Yes.

Can we use a type 1 or 2 solder paste? a) No. These are not recommended for fine pitch. Type 3 or 4 is the recommended solder paste for LLP packages.

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#43531

Can you wave solder this part | 23 August, 2006

Nope, and, Be careful with the "grid" on your stencil for the big centre pad - I could not find the stencil recommendations. I use a similar part by Cygnal (CP2101). Next time I will reduce the apertures by 50% from their suggested layout. We had floating and bridging issues with a 0.005" stencil. Simply too much paste underneath. Yes, fillets are fun too.

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aj

#43532

Can you wave solder this part | 24 August, 2006

we had problems with fillets and shifting aswell,but the recommended print aperture is reduce thermal pad by 35% and offset the lead print by 3thou...i.e. 3thou over hang on outer edge of lead which also moves the paste 3thou in from the inner edge . We have ran over 5k like this and excellent results every time.

aj...

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#43533

Can you wave solder this part | 24 August, 2006

Darby National published stencil recommendations for their LGA in the "SMT Assembly Recommendations" section of: http://www.national.com/an/AN/AN-1187.pdf Is it possible that Silicon Laboratories published a similar document for your Cygnal CP2101?

Although we couldn't find an app note for the Cygnal part easily, "Figure 4.4. Typical QFN-28 Solder Mask" [ http://www.silabs.com/public/documents/tpub_doc/dsheet/Microcontrollers/Interface/en/CP2101.pdf ] looks like an excellent starting point for stencil design.

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Chunks

#43538

Can you wave solder this part | 24 August, 2006

I too had to reduce by 50% because of floating (0.006"). But, most recommendations are for pads with via perforations. So if you are mounting to a flat pad, reduce even more.

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RDR

#43539

Can you wave solder this part | 24 August, 2006

We reduce 50% on that pad and achieve excellent results as well. Have placed somewhere in the hundreds of thousands of these (one board we have has 75 alone!!!) We do nothing special for other pads.

Russ

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#43564

Can you wave solder this part | 24 August, 2006

Dave, Cygnal was taken over by Silabs. I based my design on the second link that you provided. Tell me folks, are you using one large pad with only the stencil having the grid, or are you actually breaking up the large pad into grids with mask around them and a reduction for the stencil? In my original "problem" design I followed the guidelines on page 10 of the link Dave provided, i.e an array of 3 x 6 with dimensions of 0.6mm x 0.3mm. I see I have another one, (28 pin) coming up and the large pad is 2.5mm x 2.5mm. I have changed the array to 4 x 3 with dimensions of 0.45mm x 0.3mm.(I know; I didn't go 50% like I said). In line with our various educations: What say ye olde fellowe? Whadyareckon buddy/doll? Whatya thinkin' mate?

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aj

#43567

Can you wave solder this part | 25 August, 2006

Russ,

Do you use on print offset on the leads?

I kepp reading about the fact that it is not possible to form a fillet on the sides but we seem to have no problem by using the offset.

One board in particular needed these fillets to function >

aj...

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#43569

Can you wave solder this part | 25 August, 2006

We'd do it the same way that you did, except apply no solder mask over the heat slug.

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Chunks

#43575

Can you wave solder this part | 25 August, 2006

One big pad, one 50% app in the stencil.

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RDR

#43577

Can you wave solder this part | 25 August, 2006

We sire don't AJ, We use a single large aperture in center and the outer pads are just reduced our standard which is I believe about mil off of each side or 2 mils in X and Y.

As far as side fillet, sometimes we get them sometimes we don't, I attribute this to the condition of the part and have never really looked into or evaluated.

Could you explain this offset to me?

Thanks

Russ

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RDR

#43579

Can you wave solder this part | 25 August, 2006

We use a single large pad on board and reduce stencil aperture 50%.

If you mask/reduce the thermal pad the solder will not wet out to edges and you will still see the part standoff with the open joints. the purpose of reduction is to wet the paste out to edges causing the part to be pulled down onto board.

Russ

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reflow oven profiler