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Tilted/Slant SMT Component Specs?

ianchan

#19281

Tilted/Slant SMT Component Specs? | 26 March, 2002

Hi Guys,

(Note: We are not talking about bill-board RES/CAP, we are talking about Z-axis slant/tilted RES/CAP with respect to the PCB pad Z-axis plane).

1) We ref through the IPC-A-610C specification "bible", and can not find a "chapter/verse" that specify SMT chip component (RES/CAP) specifications for slant/tilted tolerances?

2) What we found was the specs ONLY for slant/tilted PTH component, section 5.2.6, 5.2.8, 5.2.9, from the pages of IPC-A-610C.....

3) As SMT components are meant to sit flush to the PCB pads, we do not believe that the slant/tilt specs of PTH components, apply for SMT components.

4) Are we correct in this analysis approach (item.1-3)?

5) Anyone have practical experience for slant/tilted SMT components, in the area of post-reflow oven QC inspection specifications, that we can utilize as QC inspection criteria?

6) The solder fillet looks fine by IPC-A-610C standards, only that the RES/CAP have tendency to be slant/tilted. We know the root cause and are in midst of applying technical remedy, in the meantime, any way to get a QC waive for such slant/tilted RES/CAP, within IPC-A-610C acceptance inspection criteria?

All help appreciated, guys! thanks in advance

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#19296

Tilted/Slant SMT Component Specs? | 27 March, 2002

It is certainly a process indicator. What is causing this condition? Is it a chip that has its toes over the edge, edging towards tombstoning?

Contact: * Jack Crawford [ JackCrawford@IPC.ORG ] * Mel Parrish [ mparrish@SOLDERINGTECH.COM ]

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ianchan

#19298

Tilted/Slant SMT Component Specs? | 27 March, 2002

After a whole night's self review, I think we can term the slant/tilt as "floating 0805, yet end-terminals have acceptable solder joint formation".

the width portion of the 0805 RES/CAP is (floating)elevated from the PCB pad, yet both (width) terminals see evident solder fillet. The solder fillet look like "excess solder" condition that are still within IPC specs of "solder does not flow/extend onto the TOP of the 0805 "ceramic" component body.

It's just that despite the acceptable solder joints at the end-terminals, we see one end-terminal higher than the other end-terminal, and there is a "gap-hole" in between the 0805 component base & the PCB pad surface.

We analyzed the solder paste as excessive for this pad size, paste height is measured along 7mils~8.5mils. We use a 8mils Stencil.

We noted the paste print out, has "out of pad size" paste print. Stencil aperture is larger than the actual PCB pads. We can find that pads volume deposit is thus uneven in print.

We will be changing to a new 6mils stencil, with aperture opened to match (might be smaller than)the PCB pads size.

~~~~~~~~~~~~~ Bottom line :

We can not find the IPC-A-610C specs that dictates how much can a RES/CAP be "tilted/slant/floated" relative to the Z-axis plane of the PCB pad surface, before it is deemed a defect under IPC-A-610C inspection criteria for PCB Assemblies?

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#19299

Tilted/Slant SMT Component Specs? | 27 March, 2002

Touch!!! Unwise. Stop. Do not restart.

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ianchan

#19300

Tilted/Slant SMT Component Specs? | 27 March, 2002

Huh? wats'ta mean??? "stop"???

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ianchan

#19312

Tilted/Slant SMT Component Specs? | 28 March, 2002

Hi Dave F,

we tried to contact: 1) Jack Crawford, 2) Mel Parrish, but the (above supplied) links provided give error messages, is it possible to help relay this posting to them respectively for their help/review?

thanks.

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#19316

Tilted/Slant SMT Component Specs? | 28 March, 2002

Don't be concerned. Brian and Neil don't allow us to link directly to email from SMTnet [even though from the way the link changes color you'd think you could. They do this to subjugate the huddling masses and lord the power of cold fusion over us. "And how d'you get that? By exploiting the workers! By hanging on to outdated imperialist dogma which perpetuates the social and economic differences in our society! If there's EVER going to be any progress ..."]

Anywho, you need to copy the email address from SMTnet and paste it into your regular email composition software to get around this.

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#19326

Tilted/Slant SMT Component Specs? | 28 March, 2002

I realize that this is sort of off-topic, but do you have scads of solder beads (mid-chip solder balls, whatever you like to call them) with that stencil design? If not, would you mind sharing which paste it is that you are using? Email if you like. I'm just wondering if you're using one of those so-called zero solder balling pastes and it actually works. Thanks.

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ianchan

#19340

Tilted/Slant SMT Component Specs? | 31 March, 2002

Ooooohhh...K..... roger that, over.

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ianchan

#19341

Tilted/Slant SMT Component Specs? | 31 March, 2002

Nope, we do not have solder beads, like we said, what we have are near perfect solder fillets except for the portion where the component is "floating OFF" the pcb pads. We are now mucking through the IPC-A-610C for specifications dictation on "tilted/slanted/floating" RES/CAP components...funny how we have'nt found anything that resembles a acceptance specs, yet...

btw, we are using OMG (Mircobond) WS300 solder paste, its a Sn63/Pb37. There is "silver content" variant too. Both types are water soluble pastes.

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