I will leave it to others to come back on specifics based on their current
experiences, the most helpful suggestion I have overall is to keep in mind,
and as the background to all your decisions, is:
No clean is a much more critical process than using a strong flux and
cleaning it off.
What is a strong flux? Almost any which is not a no clean.
A more critical process is one where all your process windows are smaller and
therefore all variations - controlled or uncontrolled/unknown - become much
more critical/sensitive. So on this basis the answer to nearly all your
questions is yes.
You have to have a much better understanding of all the things that could go
wrong because they are more likely to. On this basis a pragmatic response is
to reduce the number of things you have to try to understand by having less of
them. ie not 8 solder resists........ Also board finishes, storage, process
parameters, components, layouts, etc etc etc.
And the good news:
You are not the first to go down this route and can therefore benefit from the
cumulative experiences of your predecessor Technetters.
I suggest your suppliers should also be near the top of your list to tap for
advise and recommendations. The quality of their reponses will help determine
who you want to work with as you change over to make the best informed
decisions for your line. Also later on no way do you want adversary situations
when you start to have inevitable startup problems.
Hope this helps.
In a message dated 29/01/99 11:36:56AM, you write:
> Greetings Techno's;
>
> I am member of a No Clean Sterring Committee that is reviewing our
> internal process that we are presently processed to perform, and
> determine what is the best approach and what it would it take to
> change over our lines to "NO CLEAN". The industry and our owners are
> driving this change. The following are some questions I have and
> wonder anyone out there that has experienced similar changes recently
> a who would like to share their "Lessons Learned" with me. We are
> building a mix technology, (i.e.; SMT only, SMT+thru hole, and thru
> onle). Our products have various finishes, (i.e., potting and/or
> conformal coat)
>
> The following are some questions I have come across:
>
> 1) What is the best No Clean Flux that works well with organic coated
> boards. We are looking at our suppliers using Entek CU-106A organic
> coating?
>
> 2) Does the level of preheat that the organic coating is exposed to
> detrimental to the shelf life of the coating? If so, what is the
> amount of time period between IR reflow and wavesolder for a board
> that has been exposed to IR reflow for SMT purposes? We are
> experiencing poor solderability on the thru-hole components to the top
> side of the circuit side.
>
> 3) Does the type of solder mask that is on the print wiring board
> surface have any effects on the PPM level for solder balls? Does
> anyone have any experience on this subject?
>
> 4) Does it hinder a companies purchasing power to narrow your
> selection of types of solder mask? We presently have 8 different
> solder mask finishes on our various products.
>
> 5) Does anyone out there have any experience on the Paste Inspection
> system made by General Scanning? We recently brought a GC8200 in house
> for evaluation. Initial data reflects that the measurement readings
> obtained for CpK and Gage R&R are not acceptable. We used the
> theoretical volume to calculate the mean and standard deviation. Is
> this the accurate way of measurement? If someone out there that has
> experience with this system that can help me, please respond.
>
> I took up your time enough. Have a good day.
>
> Thanks
>
> Donn Steffen
> Senior Quality Engineer
> VDO Control Systems, Inc.
> Auburn, IN
>
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