Steve, Guy, et al.
It may be worth mentioning that ANSI/ASQC S1-1996 describes skip lot
sampling plans, analogous to continuous sampling plans for parts produced
in a stream. The simplest plans call for inspecting incoming lots until
some number, called the clearance number, of consecutive lots have passed,
after which only some fraction of lots, selected at random, get inspected -
until there is a rejection, at which point all lots are inspected until the
clearance number of lots have passed. There are more complicated plans,
but the simplest ones may already require enough administrative attention.
The user has lots of choices for clearance number and fraction inspected,
depending on required levels of quality. Lou Hart
-----Original Message-----
From: Stephen R. Gregory [SMTP:[log in to unmask]]
Sent: Thursday, July 05, 2001 8:18 PM
To: [log in to unmask]
Subject: Re: [TN] J-STD-002 and -003 solderability testing...
Okay, I know I'm going to piss some people off...I'll test components from
AVX, Murata Erie, Kemet, Vishay, Texas Instruments, Amkor, Signetics,
National Semiconductor, Fairchild, Motorola, etc...etc...and then I'll
find
that everything is okay... DO YOU THINK THIS IS NECESSARY? BE REAL!!!!
Don't you think that solderability is foremost in the vendors of these
components? Do you ACTUALLY think that we have to double-check what they
say
they are going to provide to us? That we have to check everything they
provide to us?
I'd like to hear from component manufacturers...do we need to check your
stuff? If we do, I would be ashamed....
-Steve Gregory-
> J-STD-001C 5.2 Solderablity: Electronic/mechanical components and wires
to
> be soldered shall meet the requirements of J-STD-002 or equivalent . . .
I
> do not see a requirement for 100% solderability testing. I am not a
> proponent of 100% solderability testing.
>
> I submit that the standard requires you to "know" that the part you
intend
> to use in production be solderable as defined in J-STD-002. I believe you
> can "know" this through statistical methods and sampling.
>
> I set up a sampling plan for our board suppliers that specified sampling
by
> date code. So, in the case where our supplier manufactured many different
> part numbers our testing requirements were reduced. We found the system
to
> be effective (identified defective product and minimized inspection and
> test), and our customers approved the system.
>
> I think the part of the standard that might be getting you is 5.4
> Soderability Maintenance: . . . ensure that all componets, parts, leads,
> wiring . . . are solderable.
>
> But, I interpert this paragraph as addressing storage and handling. It
does
> not mention testing or inspection. This paragrah requires the
manufacturer
> to "know" that storage and handling has not degraded the components to be
> soldered.
>
> The end item acceptability criteria in the J-STD-001 and IPC-A-610 assume
> that the materials and methods used conform to the requirements of the
> standard. This is not a version of process control it is a prerequisite
for
> compliance.
>
> A means by which we can provide assurance is SPC, rather than 100%
> inspection. One of the four essential techniques in Statistical Quality
> Control (from the Western Electric Handbook, 1956 based on Shewhart's
work)
> is Statistical Sampling Inspection.
>
> Guy Ramsey
> Senior Lab Technician / Instructor
>
>
> E-Mail: [log in to unmask] <mailto:[log in to unmask]>
> Ph: (610) 362-1200 x107
> Fax: (610) 362-1290
>
<< File: ATT00000.htm >>
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
