<quote>Sounds to me that each manufacturer is building his own system and
that often it is ERP capable dependant, and that it also has some depth
where each one is more or less performant and accurate.</quote>
Yep. As you identified, there are methodologies for measuring defects of
products or services in general, but I am unsure as to the value in having a
standard on how best to measure defects specifically for PCBs.
Many factors to consider. Data collection and analysis efficiency and
effectiveness is a major one. Another is the resources available to do
something with the information. Performing a root cause analysis and
corrective action on each defect when you have a hundred a month is not
feasible, but if it only ten, go for it.
As I have mentioned here before, I am currently using the three metrics of
total work orders with at least one defect, total PCBs defect and "impact".
The first two are simple to understand. For the latter, I use the term
"impact" because to say cost is misleading. I do use the financial value
calculated as a percentage of the price (for a rough gross cost) factored
from where it was taken from the process. Some would say the result is the
cost of the scrap, plus an administration factor for each instance. I say
so what. While the end result of Quality is a control to reduce cost and
improve performance, I personally am not concerned about the dollars unless
I am going for a pay raise and need to justify my existence based on a
common value that relates to my paycheck.
What I do care about is the impact that quality has on the company. PCBs
are priced based on impact. Higher technology (additional processes,
tighter design parameters, additional layers, etc.), quicker turn around and
less standard processing (lower volume, infrequent orders) increase the
impact on the company. Best-case, defects are the last resort as an
indicator of a process deviation, with process control parameters and
techniques akin to SPC in place to detect variations before defect. Yeah,
so anyway, using PCB defects as an indicator of process deviation, I want to
focus on the areas of the most impact, hence using the cost factor. I have
11 instances of 2 PCBs each with poor legend, the impact is $2,000. I have
2 instances of multilayer pressing issues, the impact is $20,000. The
dollar symbol introduces unnecessary emotions. All that is important is
that one number is a lot bigger than the other. In the same manner, I am
not so much concerned about initially capturing one multilayer issue was a
result of operator error (sorry, training) and the other from equipment
malfunction (oops, preventative maintenance). The impact itself will
trigger an investigation, root cause, remedial and corrective action cycle
which will raise those issues so as to try and stop the problem from
impacting the company again.
I am using manual logs and excel and then linking it to our MRP to perform
the calculations. Not the most sophisticated system, but it is appropriate
for our current needs. The amount of time I have to focus on what is wrong
is balanced by the amount of time I have to fix the problems. And the fact
that I just drolled on about it maybe says I should get back to either one
or the other. ;)
Cheers,
Chad Renando
Quality Manager
Precision Circuits Pty Ltd
Ph: +61 3 9877 3222
Mo: 0417 593 337
Fax: +61 3 9877 5079
www.precisioncircuits.com.au
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roland Jaquet
Sent: Thursday, 8 June 2006 1:13 AM
To: [log in to unmask]
Subject: Re: [TN] How are PCB & Assembly manufacturers measuring scrap?
Thank you fro the info, but yes this is for PBA only
I may sound old fashioned, but I am looking for a management standard /
industry recognized system for Rejects and Defects for Bare PCBs.
I know the subject has been raised before and as most things, it is coming
back.
The way PCB manufacturers are calculating Rejects & Defects from what I seen
and used for many years, is not at all consistent.
Companies are more aiming on First pass Yield, but below that it is getting
blurry as for others:
Some are talking in Rejects, and not considering defects, even so we know
often the number of Defects could be double the number of Rejects.
There is Internal Defects, Customer Defects, Internal Rejects and Customer
Rejects. From what I seen, internal to Customer ratio is of about 10 to 100
times. I.e. If PCB manufacturer says he has 0.1% rejects at the customer
side, it could mean 1 to 10% Defect in production.
Now, regarding the way to value those rejects, some people are accounting in
finished product value (sold price) at any given stage of manufacturing,
and/or calculated at cost of production and material.. Now some will
eventually consider the fact that during the time they were manufacturing a
reject, they could have done a good board! Adding the re-make cost!
Same for defects, and reworks costs and so on..
Isn't there someone who was able to put some order of logic into all this?
What about reject forecasting?
- i.e. by process such as Panel Plating versus Pattern?
- Additive / semi-Additive?
- Positive / Negative Photoresist?
- Liquid versus Dry Film Resist?
- ...
Sounds to me that each manufacturer is building his own system and that
often it is ERP capable dependant, and that it also has some depth where
each one is more or less performant and accurate.
Meilleures salutations
Very Best Regards
Rol@nd
www.PCBspecialist.com
Roland Jaquet
14 Champ Budin
1258 Perly, GENEVA
Switzerland
Tel +41-22-880-0405
Fax +41-22-880-0409
Mobile +41-79-203-3723
There are three constants in life...
Change, Choice and Principles.
Stephen R. Covey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Wednesday, June 07, 2006 4:17 PM
To: [log in to unmask]
Subject: Re: [TN] How are PCB & Assembly manufacturers measuring scrap?
The work and documents seem more focused on assembly rather than bare board
calculations. Is there work being done on bare board rejects?
Franklin
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Kraszewski
Sent: Wednesday, June 07, 2006 9:01 AM
To: [log in to unmask]
Subject: Re: [TN] How are PCB & Assembly manufacturers measuring scrap?
See the link
http://www.ipc.org/committeedetail.asp?Committee=5-22G
Rich K / KEDS
260.925.8719
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Tuesday, June 06, 2006 2:53 PM
To: [log in to unmask]
Subject: Re: [TN] How are PCB & Assembly manufacturers measuring scrap?
Technical Committee 5-22G??? Which one is this?
Franklin
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roland Jaquet
Sent: Tuesday, June 06, 2006 12:14 PM
To: [log in to unmask]
Subject: Re: [TN] How are PCB & Assembly manufacturers measuring scrap?
Dear Jack,
Thanks to Denny I learn there is an IPC committee 5-22G in regards to
Production scrap (Rejects) and this subject is of acute interest to me as I
believe there is some major flows in Bare Board Manufacturing measurement of
Defect and Rejects.
I do not know how to get information on what has been done and what I could
read in order to follow the path of the wise men..
I seek to make measurements of Rejects and Defects at the Electrical Test
level (keeping in mind we are on Bare Boards).
I would appreciate your help as I would appreciate anyone's input as well.
Thank you very much
PS I am a member of EIPC
Regards to Denny, and thank you.
Meilleures salutations
Very Best Regards
Rol@nd
www.PCBspecialist.com
Roland Jaquet
14 Champ Budin
1258 Perly, GENEVA
Switzerland
Tel +41-22-880-0405
Fax +41-22-880-0409
Mobile +41-79-203-3723
There are three constants in life...
Change, Choice and Principles.
Stephen R. Covey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: Thursday, April 20, 2006 4:18 AM
To: [log in to unmask]
Subject: Re: [TN] How are PCB & Assembly manufacturers measuring scrap?
The assembly side PWB manufacture has worked hard to quanify yield in terms
of "defects per million opportunities - DPMO". While this is not
actually a
measure of scrap, this does even out differences between simple and complex
assemblies
Recently, the same group has started to try to quanify board fab in some
similar terms to DPMO. Board fabrication is not so easy to quantify
as
it is
harder to define an individual "opportunity".
At Apex/Expo time, this group was collecting the defect codes from several
board fabrication shops to try to get a feel for some metrics the committee
could track. Anyone interested should contact IPC Committee 5-22G under
Greg Hurst of BAE Systems or IPC Technical Staff LIason Jack Crawford, as a
start.
Denny Fritz
MacDermid, Inc
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