Daniel,
First, I would like to thank you for the opportunity to steal away from my
otherwise hectic routine to answer your questions. As a matter of fact,
anything that pulls me away from my normal routine is appreciated.
Second, I believe that you have probably stumbled across the most well
versed people with the highest grade of information possible to answer your
technical (as well as political, theoretical, hysterical, and cultural)
questions completely and accurately.
Working for a company who manufactures finished PCB products (Burn-In
boards, to be exact), I think I have a decent knowledge of what processes
are needed to manufacture a Circuit Board. I know that my fellow colleagues
on the list have more experience then I, and I will bow to their teachings
if they find contradictory statements in my explanation.
Question 1: Most of your process is correct, except for #3 (Dry Paste) which
isn't necessary, and would actually be detrimental, as the moisture in the
solder paste is flux (and other things) and would make the solder paste
virtually unsolderable. (There was a discussion recently about the life
expectancy of screened paste and the impact on the solderability) Also, #6
is unnecessary, as the wave solder process runs the solder over the bottom
of the board, and the components are held in place by gravity. Also, there
are some other minor steps that I feel need to be mentioned, Touch-up of the
boards, Quality Control, and Test. Of course, if your processes are correct,
you might be able to get away from the Touch-up (removal of excess solder,
adding solder) process all together. We haven't gotten to that point yet,
but I can taste it! QC and Test are vital, as you don't want to send your
customer a widgit that doesn't work.
Question 2: Batch sizes can be as low as 1 pc. (qualification pc.) or as
large as you want to think. I know of some companies local whose batch sizes
are in the 10,000's. Think about how many widgits are in your local store,
how often they are bought, and how many stores worldwide carry your
particular widgit. This will give you a base number for how many units are
sold worldwide, then you have to calculate your market-share (never an easy
thing) and how many other competitors are making widgits just like yours. I
would say for the widgit you are basing your report on, a batch size could
be 10,000 pcs a month.
Question 3: Setup and run times vary on a) size of company, b) equipment
being used, and c) how well you know your processes. I would say that a
medium sized company with fairly updated equipment and a good knowledge of
processes could probably push out 10,000 pcs a month, if it is the only
product they are producing, as this reduces the setup time, and it would be
able to process the same product around the clock. Each of the processes
except for the Quality Control can be an automated step, reducing the down
time due to breaks and lunches. Even the QC part can be partially automated
due to AOI (Automated Optical Inspection), but there still has to be someone
there to verify the machines findings. As I see it, my theoretic company
running at full capacity should be able to process 14-15 parts per hour with
little downtime running 3 shifts 7 days a week. (What can I say, I am a
slave driver!)
Question 4: There are many different PCB manufacturers across the world,
including cheaper (and I believe this is true in every sense of the word)
manufacturers overseas in Asia (another big topic of discussion recently
that turned into a pedestal of political opinion). Most of the widgit
manufacturers outsource the PCB and parts, as they are not manufacturers of
PCB and parts, only the finished product. My company procures several
outside sources to manufacture PCBs, purchases parts for suppliers and
distributors, and only does the design of the PCB and the manufacture of the
finished product, although we have in previous history maintained our own
PCB shop and supplied ourselves. It comes down to business basic #48, which
is to never get into a business you know nothing about and cannot focus 100%
of your resources to learn it.
Question 5: There are a multitude of companies that manufacture electronic
components, including the horn and possibly the ionization chamber (I am
sure my esteemed colleagues would actually be able to find a company that
specializes in ionization chambers, and thanks for the tip on the "Short
Sniffer", as I am intrigued by it and plan to procure at least one in the
next week).
Finally, I want to say that the University of Cincinnati is a fine
establishment, my sister graduated from there some years ago with a
Bachelors in Business Something-or-Other, and I appreciate the opportunity
to answer some if not all of your questions. If you need any more
information, you can feel free to contact me off-line and I will do my best
to answer your questions.
Thanks,
Rob Eason
Dir of Mfg
CEIBIS - Cody Electronics, Inc. Burn-In Solutions
Santa Clara, CA
-----Original Message-----
From: Daniel Themann [mailto:[log in to unmask]]
Sent: Wednesday, August 14, 2002 3:30 PM
To: [log in to unmask]
Subject: [TN] Smoke Detector Circuit Board
Dear List,
I recently contacted the Australian Surface Mount and Circuit Board
Association
with some technical questions relating to PCB manufacturing, but their
instructors are currently traveling and Dianne Hunt recommended that I
contact
Technet. I am a student at the University of Cincinnati and my teammate and
I
must write a report describing in detail how a circuit board is
manufactured.
I recognize that you are certainly not employed to assist college students
with
technical questions, but if you have a moment and could address the
following
points without too much trouble, I would very much appreciate your help.
Our circuit board comes from a smoke detector and is approximately 1.5" by
3.5". It contains both surface mount (resistors, capacitors, etc.) and
through-
hole components (ionization chamber, electric horn, battery contacts, etc.).
These components are placed on ONE SIDE ONLY. We have tentatively drawn up
the
following process steps.
1. Screen Print Solder Paste on side one
2. Place surface mount components on side one
3. Dry paste
4. Reflow Solder
5. Insert through hole components on side one
6. Invert Board and apply adhesive on side two
7. Wave solder
8. Final Clean
Question 1. Does the process described above seem reasonable? In
particular,
is step 6 necessary if all components are applied to one side only?
Question 2. What type of batch sizes would be reasonable in "low volume" and
in "high volume" processes for a board of this type and size?
Question 3. What would be approximate setup and run times for each process?
We
need these times both for our process route sheets and as input into our
cost
analysis.
Question 4. Is it possible to purchase the board itself (without the
components
attached) from an outside vendor and to simply attach the components
in-house?
Or does the manufacture of the board and the soldering processes by which
the
components are attached constitute one continuous process? If the board
itself
can be purchased outside, how much might it cost given low and high volumes?
Question 5. Does you know of any companies that manufacture special
through-
hole components such as the electric horn and the ionization chamber? Do
you
know where prices on such components, and more common components such as
resistors and capacitors, could be obtained?
If you could spare us a few minutes of your time we would be most grateful.
If
you feel that you can assist with some questions, but not with others we
would
still appreciate any insights you can offer. If you know of anyone else who
might be able to help, please feel free to forward this message on. The
project is due in less than two weeks so timely responses would be
fantastic.
Thank you in advance for your help.
Sincerely,
Daniel Themann
Arthur Jackson
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