TECHNET Archives

December 1998

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 22 Dec 1998 07:50:00 EST
Content-Type:
text/plain
Parts/Attachments:
text/plain (102 lines)
In a message dated 12/21/98 8:56:34 PM US Eastern Standard Time,
[log in to unmask] writes:

> Paragraph 4.2 of J-STD-001B says flux shall conform to activity levels L0 or
>  L1 and if other activity levels are used, data shall be available showing
>  compliance with testing as per appendix D.

The logic behind this requirement was that if you were manufacturing with a
flux that was halide free (L0) or only a small amount of halide (L1), then the
residues were benign and you did not have to prove that your flux was benign.
Theoretically, that assessment was made when the flux manufacturer qualified
the flux to J-STD-004.  Therefore, why go through it again.

I question that logic as I have seen lots of electrochemical failures coming
from L0 and L1 fluxes, when used improperly or without enough advance process
development work.

>  D1.1 then says that this appendix is only required for Class 3.

My understanding of the hierarchy of the IPC documents is that the text in the
specification prevails over than in the Appendices.   Keep in mind that the
Appendix D test is only *one* way to show that the flux and other materials
you are using are compatible with each other.  See the wording in paragraph
3.4.  Everyone is required to use materials that are compatible with each
other.  Class 3 manufacturers are required to have objective evidence on hand
of this compatibility.  It suggests that the Appendix D is one acceptable way
to demonstrate compatibility.

>  What does this mean, in practical terms, if you are using an organic flux (
>  Multicore Hydro-X 20 )  for wave soldering to Class 2?

I think it depends on how closely you interpret the *shall* in that statement.
Strictly speaking, if you are manufacturing to class 2, then the whole
statement is a *suggestion* for you.  The way the J-STD is written, the shall
applies as a requirement only to class 3 manufacturers, and for class 2, it is
a really, really, really good idea.  But, if you don't wanna, no problem.

>  Like most organics, this is an ORH1 type flux.
>   Does this comply to Class 2 requirements if the post-solder cleanliness
>  requirements are met ?

If you are manufacturing to any class with a type H flux, and you are only
relying on the post solder cleanliness requirements (the ROSE test), then you
are playing with fire.  It is only a matter of time before your assemblies
fail from electrochemical mechanisms (corrosion, metal migration, leakage).

What kinds of testing have you done to ensure that the manufacturing system
you have NOW has compatible materials?  What kinds of data does your customer
need to see to be assured of compatibility?

From my position, I see more and more assemblies, class 1, 2, and 3, that are
failing in the field in shorter and shorter time spans because manufacturers
either don't know how to test for compatibility, don't know how to specify
cleanliness, or don't want to spend the money to understand their
manufacturing process.  Ron Daniels, editor at Circuits Assembly, sees the
same increasing trends in field returns.

Forget about the wording in the J-STD.  Do you understand your process and
have you done enough testing to assure yourself of reliable function
throughout the design life of the product.  Will people die if you are wrong?
Will your employer shoot you when thousands of units have to be recalled from
the field?

From what I have seen on the J-STD-001 development process, both the B
revision currently in place, and the C revision being worked on now, the trend
is towards greater and greater flexibility, allowing a manufacturer to define
compatibility and acceptability per agreement with their customers.  It is all
part of the migration away from proscriptive "how-to" types of specifications.
This is all well and good for large manufacturers, but the small to medium
manufacturers need guidance on what is good and what is bad and how to
determine the difference.  More testing is being taken out of the C revision
drafts under the ***assumption*** that "of course, the manufacturer is going
to assess quality and compatibility before starting manufacturing".  Bad
Assumption.  REAL bad assumption.

Man, I have *got* to cut down on that Mountain Dew in the morning.............

> Does anyone know of an ORLO water soluble flux?

Not that I have ever seen.  Dr. Karen Tellefsen at Alpha Metals, David Torp at
Kester, or Doug McKernan at Amtech might be able to give you more definitive
answers, but I can't imagine why one would be made.  If you are going with an
organic acid flux, you do so because you need the higher activity level for
some reason, usually a solderability challenge.  An ORL0 flux would be like
going hunting with an elephant gun, and only pellets for ammo.

Doug Pauls
Technical Director
Contamination Studies Labs

################################################################
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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################


ATOM RSS1 RSS2