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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


LLP Device

Views: 2284

aj

#40296

LLP Device | 8 March, 2006

All,

I have a problem on a new device that we have on a new product. It is a LLP (Leadless Leadframe Package) if you search in google "sda16a" you can see one.

I am finding it next to impossible to consistently achieve a good visible solder fillet along the terminal walls on the device.

I have adjusted Printer and reflow to supplier recommendations but am still getting mixed results.

To get the boards to pass all tests it is essential that this fillet is achieved.

I am usin no-clean paste with a 6thou stencil.

Any ideas please feel free to let me know.(i have searched thry some threads and there are similiar problems but no solutions)

aj

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Chunks

#40303

LLP Device | 8 March, 2006

You will not get a "visible" solder joint on this part. The joint is under the part. If you can magnify the part, you'll see the exposed lead is not plated.

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#40304

LLP Device | 8 March, 2006

Chunks nailed it. You should not expect to see a perfect side fillet on this part, especially using no-clean, it's probably bare copper, hard to wick solder up the side of the lead.

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JAX

#40305

LLP Device | 8 March, 2006

Part is most likely a QFN package. IPC-610-D has standards on solder quality for this new type of package.

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dougs

#40315

LLP Device | 9 March, 2006

one point to remember is to have a large stencil reduction on the thermal pad, you need to reduce the solder volume by about 35%, if you don't you risk the solder from the thermal pad shorting out the other leads or the solder volume causing the component to lift slightly causing open circuit.

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aj

#40339

LLP Device | 10 March, 2006

Guys,

Just to let you know, I followed the recommendations from the supplier and we have very nice solder fillets now.

Thanks for all your help.

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RDR

#40340

LLP Device | 10 March, 2006

What were the recommendations?

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aj

#40372

LLP Device | 13 March, 2006

Hi Russ,

To reduce solder on thermal pad by >35% and overprint by 3thou on the leads.

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aj

#40373

LLP Device | 13 March, 2006

overprint by 3 thou on the length of leads only

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RDR

#40379

LLP Device | 13 March, 2006

Thanks A.J. knew about the thermal pad reduction but not the overprint. off to CAD!

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