Hi Inge!
Not sure what you mean by the camera in this thread. I've always thought legend ink was just for hand assembly or manual inspection.
Wayne
-----Original Message-----
From: Inge [mailto:[log in to unmask]]
Sent: Thursday, May 20, 2010 9:17 AM
To: Thayer, Wayne - IIW; [log in to unmask]
Subject: Re: [TN] Component legend marking on PWB with 0402 components
What's the minimum size of components to be correctly recognised by the
camera system ?
Inge
--------------------------------------------------
From: "Thayer, Wayne - IIW" <[log in to unmask]>
Sent: den 20 May 2010 14:45
To: <[log in to unmask]>
Subject: Re: [TN] Component legend marking on PWB with 0402 components
> You can check with other vendors. Generally we don't bother with silks
> for our designs if the parts are small--they can just get in the way. But
> some vendors offer (for a bit more money) photo-defined legend, which is
> basically a very highly pigmented LPI soldermask product. Not only can
> you image 0402 outlines, you can make legible (for those under 40)
> reference designators for them!
>
> Wayne Thayer
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> Sent: Wednesday, May 19, 2010 6:59 PM
> To: [log in to unmask]
> Subject: Re: [TN] Component legend marking on PWB with 0402 components
>
> Hi,
>
> Yes, I have the same issues. Marking for 0402 and smaller is "Very
> Difficult". Having looked at a lot of boards for assembly I also find 0402
> marks result in "Less Than Dense" packing. Folks that use and mark 0402
> could usually have used 0603.
>
> Here is an interesting side note:
>
> If you look at what these new silk screen printers can do from a
> marking standpoint they are amazing. The problem is the interface media to
> the fab house is typically gerber format and in house design rules trash
> thin lines or lines close to pads. There almost needs to be a complete
> re-think about silk screen rules as these new printers are a light year
> ahead of old silk screen technology.
>
> Bob Kondner
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Temkin, Gregg
> Sent: Wednesday, May 19, 2010 6:49 PM
> To: [log in to unmask]
> Subject: [TN] Component legend marking on PWB with 0402 components
>
> On a first shipment from a new PWB supplier, we found all the 0402
> component
> outlines deleted from our legend layers. The PWB vendor said they
> automatically deleted the marking during DFM because it exceeded their
> manufacturing allowances and could have resulted in ink covering a portion
> of the pad.
>
> Our in house PWB designer uses a program to develop his pad and marking
> dimensions. The program would not generate a marking outline for this
> device, so he designed the outline to be the courtyard plus some
> manufacturing allowance.
>
> Other vendors have supplied with PWBs with the same outline marking
> configuration; seemingly without any problem.
>
> I've reviewed IPC-7351A, but couldn't find mention of PWB marking
> recommendations. Is there guidance that I missed of is there another
> document I should be looking at? Is it generally assumed that outline
> marking of 0402 and smaller devices is impractical? Is placing a remotely
> located legend the best way of showing 0402 placement and orientation?
>
> Thanks for your help.
>
> Gregg
>
>
>
>
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