Hi TechNetters,
In respect to Scott and Mike's comments, I will proffer the following
observations:
The surface energy issues of the solder mask will be dictated to a larger
extent, by the proportional amount of de-wetting and de-bubbling agents
within the formulation. Likewise, the possible "squirting" of a little
something to get the curtain coater working well, will fundamentally
influence the properties of the mask.
Improper curing will also have a serious impact on this issue.
Gloss v matte v semi-matte v semi-gloss?? Tricky ain't it. We have a problem
convincing some customers in France, that the issue of coating adhesion is
most commonly caused by issues with the mask rather than the coating. Viz: A
conformal coating is not an intelligent product. It sticks to Copper,
Tin-Lead, FR4 etc., but it doesn't stick to your resist - how does it know
the difference? When quizzed, we established that the solder mask in
question - which works fine with our coatings elsewhere - just won't work in
France but the supplier has - and I quote - more than 150 different
varieties of the same resist! Wow - no wonder you have trouble making this
lot compatible.
Further, we know that mask formulators may use fluorine additives and if
these are not VERY carefully controlled, they may leave little fluorine legs
that only other fluorines will attach to - but nothing else?
And as if that wasn't enough, along comes the assembler who liberally
applies a flux, of dubious parentage, which has less than 2% solids requires
a higher pre-heat to drive off the excess liquid and which gets into the
mask - with who knows what sort of reaction?
Now everyone asks about the qualities of the conformal coating? REMEMBER
PLEASE, we coating folks make coatings that have to be re-qualified annually
(or at least re-certified) - not once for life, like a resist. Our material
has remained unchanged for over 20 years because of, and in order to
maintain, it's qualification.
Finding and establishing a compatible process is now a major issue - and I
will only repeat my often recommended procedure to use SIR testing to
ANSI/IPC-J-STD001 Appendix D for Process Characterisation.
Regards, Graham Naisbitt
__________________________________________________________________________
[log in to unmask]
Concoat Ltd
Alasan House, Albany Park
Camberley GU15 2PL UK http://www.concoat.co.uk
-----Original Message-----
From: Challoner, Scott <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 04 June 1998 19:42
Subject: Re: [TN] ASSEM: MATTE VS GLOSSY
>Would the same principle apply to conformal coating?
> ----------
>From: Mike Barmuta
>To: [log in to unmask]
>Subject: Re: [TN] ASSEM: MATTE VS GLOSSY
>Date: Thursday, June 04, 1998 1:15PM
>
> Robert: Matte soldermask has a higher surface energy than gloss
>mask.
>Because of this it wets more easily and holds a more uniform thicker
coating
>of flux than the gloss. You can use the analogy of a waxed car (low surface
>energy)it does not wet and retain a coating of water, it beads up and runs
>off,
>same thing for the gloss mask.
> Since the matte mask holds more flux, wave solder settings like
>preheat/conveyor speed have to adjusted (more preheat/slower speed)to drive
>off
>the volatiles in the heavier coating of flux before contacting the
>solderwave.
>Also flux applicator settings, especially spray type can be adjusted to
>control
>the amount of flux on the board.
> Glossy mask run at these same settings could dry out and create
>solder
>webbing or bridging when run thru the wave. Glossy mask also has a greater
>tendency to form solder balls which may require additional adjustments of
>the
>the settings to minimize.
> With one standard mask your assembler will not have to do as much
>process adjusting and will probably provide a more consistent product. My
>guess
>is they would prefer the matte.
>
> Regards
> Michael Barmuta
> Staff Engineer
> Fluke Corp.
> Everett Wa.
> 425-356-6076
>
>On Thu, 4 Jun 1998 05:22:57 -0700 Robert Welch wrote:
>
>> From: Robert Welch <[log in to unmask]>
>> Date: Thu, 4 Jun 1998 05:22:57 -0700
>> Subject: [TN] ASSEM: MATTE VS GLOSSY
>> To: [log in to unmask]
>>
>> Hello Technetters,
>>
>> I've been asked to forward this inquiry for a contract assembly
>> person we deal with occasionally.
>> His problem is that he has to adjust his wave solder parameters (more
>> or less preheat??) when changing between "very shiny" and "very
>> dull" solder mask on the same part number. He would like some
>> collaboration of this phenomena to help justify
>> requiring his supplier to keep all the mask the same.
>>
>> Thanks,
>> Robert E. Welch
>> Process Specialist
>> Email: [log in to unmask]
>> Modem: 804-239-9120
>> Fax: 804-237-3048
>>
>> ################################################################
>> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV
1.8c
>> ################################################################
>> To subscribe/unsubscribe, send a message to [log in to unmask] with
>following
>text in the body:
>> To subscribe: SUBSCRIBE TechNet <your full name>
>> To unsubscribe: SIGNOFF TechNet
>> ################################################################
>> Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
>information.
>> For technical support contact Hugo Scaramuzza at [log in to unmask] or
>847-509-9700 ext.312
>> ################################################################
>>
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
>text in the body:
>To subscribe: SUBSCRIBE TechNet <your full name>
>To unsubscribe: SIGNOFF TechNet
>################################################################
>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
>information.
>For technical support contact Hugo Scaramuzza at [log in to unmask] or
>847-509-9700 ext.312
>################################################################
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in the body:
>To subscribe: SUBSCRIBE TechNet <your full name>
>To unsubscribe: SIGNOFF TechNet
>################################################################
>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
information.
>For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
>################################################################
>
>
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################
|
