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May 2014

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From:
Ahne Oosterhof <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ahne Oosterhof <[log in to unmask]>
Date:
Fri, 30 May 2014 09:52:41 -0700
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That rule of thumb does not work well anymore with today's fine pitch components. At 0.125mm (5 mil) per 250mm (10 inch) it means that across a panel, which is typically more than twice that distance, the allowable error would be greater than 0.25mm (10mil). Even for parts with 0.5mm (19.7mil) pitch you would be printing between pads and causing shorts.
If I recall correctly, IPC-2222 suggests image precision on a circuit board should be whatever the drawing states. 
Now the question is: how precise can ecb-s be manufactured and how do the manufacturer and the user verify that the board is meeting a desired/necessary spec?
This can become an issue when depaneling individual boards (how close can you route or cut to the individual board edge) and when procuring a stencil that matches the board or panel.

Ahne. 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Grunde Gjertsen
Sent: Friday, May 23, 2014 3:44 AM
To: [log in to unmask]
Subject: Re: [TN] Misalignment

Hi

I assume you have a misalignment in solder paste printing due to pattern inaccuracy on the PCB.
Some of the newer printers can actually record and report the data, if not use the vision system in the pick and place machine to measure how much stretch you have from one corner to the other.
There is a guideline in IPC-2222 9.1.5 but how good accuracy you will need on a specific product depends on board size and lead pitch. 0,125mm per 250mm is acceptable as a rule of thumb and achievablefor the PCB supplier. LDI may or may not give better accuracy depending on how much the supplier compensates to accommodate  inaccuracies on the inner layers.

Rgds
Grunde Gjertsen

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lyon
Sent: 23. mai 2014 12:19
To: [log in to unmask]
Subject: [TN] Misalignment

Hi all, We printed Top side of some boards with two vendors,but only one suppier found misalignment issue. what detailsFA we can do to prove the failure caused by FAb Lyon Yuan ?? Android ????

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