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December 2009

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Subject:
From:
Robert Kondner <[log in to unmask]>
Reply To:
Date:
Tue, 8 Dec 2009 12:08:35 -0500
Content-Type:
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Ioan,

 You mention the assembler entering the BOM into their own system, you are
absolutely correct. Further we can assume very little about what their
software might or might not provide.

 The issues you bring up about the risk of buying DNI parts is very real.
The setup of AOI is very real.

 Add into to the story is the need to manage stuffing variations for parts
that do get installed.

 The best we can do is make sure the data is available and well organized. 
 
 If we do not list the DNIs then we make life difficult for the very people
who went through time and expense of getting a good system in place.

 I track, as independent controls for each part:

  1. If a part is in the Schematic.

  2. If a part is in the PCB.

  3. If a part is in the purchasing BOM.

  4. If a part is stuffed. 

 It is a lot for each part but even this is minimal. For each of the above
you need a Boolean column in your spread sheet. I use databases tools myself
with direct transfer to other tools like P&V. No spread sheets need apply.

Bob Kondner

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Tuesday, December 08, 2009 11:42 AM
To: [log in to unmask]
Subject: Re: [TN] PCB parts that are not installed

Bob,

The assembler will have to enter the BOM in their MRP system. What do they
do, enter the no-pop, so that they risk generating an order for those parts?
The inspection is now mostly done with AOI systems that inspect for the
presence of a part, and not likely for the absence, so why bother with
no-pops? Also, if no AOI is available, the inspection is either done with
masks, or based on homemade drawings showing the parts that have to be
there, with values.

Also, when programming is done, the programmer might merge the BOM with the
CAD, without checking for DNS...

Just my opinion, based on my personal EMS experience. You must have seen
more demands and statistically you could be right.

Regards,

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] 
W | www.digico.cc

N'imprimer que si nécessaire - Print only if you must


-----Message d'origine-----
De : Robert Kondner [mailto:[log in to unmask]] 
Envoyé : Tuesday, December 08, 2009 11:23 AM
À : [log in to unmask]
Objet : Re: [TN] PCB parts that are not installed

Hi,

 I disagree, showing the DNI makes it much easier for the inspection of
missing parts. Is a part location without a part a missing part or a DNI?

Bob Kondner

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Tuesday, December 08, 2009 11:04 AM
To: [log in to unmask]
Subject: Re: [TN] PCB parts that are not installed

The best method Shawn is the components that will not be populated do not
show in the BOM. Why should they be there, as they will require removal at
the assembly level anyways?

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] 
W | www.digico.cc

N'imprimer que si nécessaire - Print only if you must


-----Message d'origine-----
De : John Goulet [mailto:[log in to unmask]] 
Envoyé : Tuesday, December 08, 2009 10:59 AM
À : [log in to unmask]
Objet : Re: [TN] PCB parts that are not installed

DNI is used normally used for the specific assembly process.  

An SMT part may need to be installed after SMT for clearance of selective
solder height reasons.  

The kitting department needs to know which kit to put the part: SMT,
pre-wave, post wave, mechanical or test. 

 If the customer has the part on the BOM then it has to be purchased and
kitted but in the correct kit. 

 Occasionally there may be a manufacturing deviation to send a part with the
board separately when there was a design or part spec problem on the
prototype. 

Hope this helps. 

 J. Goulet Sr. Process Engineer 
----- Original Message ----- 
From: "Shawn Upton" <[log in to unmask]> 
To: [log in to unmask] 
Sent: Tuesday, December 8, 2009 10:36:16 AM GMT -05:00 US/Canada Eastern 
Subject: [TN] PCB parts that are not installed 

Quick question: What is the best method of specifying parts that are not 
installed on a PCB assembly?  I've used "DNI" for a while, while others 
have used "TBD" or "DNK" (for Do Not Kit).  "TBD" was used for locations 
which would be stuffed after some testing--maybe 1.01k had to be used on 
this assembly, 1.05k on another, etc. 

What is typical method on this?  For parts that are intentionally not 
installed, and parts that may be installed at a later date. 

Also, just to verify: is it generally desirably to list all parts that 
are not installed on a board?  I usually list all parts, installed or 
not, and the parts not installed are specifically listed as "Do Not 
Install", so as to make it clear that they are DNI'd. 

Shawn Upton, KB1CKT 
Test Engineer 
Allegro MicroSystems, Inc 
[log in to unmask] 
603.626.2429/fax: 603.641.5336 

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