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August 2000

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Subject:
From:
Mike Fenner <[log in to unmask]>
Reply To:
Mike Fenner <[log in to unmask]>
Date:
Fri, 4 Aug 2000 15:41:13 +0100
Content-Type:
text/plain
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text/plain (121 lines)
Don't overlook that you are removing both the organics in the solder
paste and the metal (spheres). You certainly need to shake or blast
these off, and you will need to filter down to your particle size on
any effluent, in addition to any chemical processing needed.

Your concerns over ultrasonics are understandable, but I think
demonstrate how perceived industry wisdom can persist beyond its use
by date. There have been several studies in this area going back so
far I can no longer remember who did them. ICI for sure, but I think
the late GEC Hirst Research was also involved. The conclusion was that
high frequency 70kHz systems (ie current machines) are OK compared to
the then 40KHz, the concern over wire bonds etc was misplaced, save
only that a poor quality wire bond might fail on cleaning rather than
in service.

Hopefully other SMARTIES have a better memory/documentation than me
and can cite proper references.

Mike

----- Original Message -----
From: "Martin Bourke" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, August 04, 2000 11:55 AM
Subject: [TN] Cleaning Of Misprinted Boards


> I am trying to source a system to clean misprinted PCB's from an SMT
> manufacturing process. The system needs to have the capability to
remove
> both solder paste and (or) glue. It also needs to be able to cater
for a
> wide range of double sided PCB's which are already built on one side
using a
> No-Clean soldering process.
>
> We are currently using a manual washing process which consists of a
soft
> brush which has a solvent is pumped through it ( Axarel 2200). The
slovent
> is circulated through a large filter and re-used. The boards are
passed
> through an Aqueous wash before going back into production.
>
> Option 1 - Ultrasonic's
> I have some concerns about the use of Ultrasonic's because we
assemble a
> wide variety of products for various customers ranging from RF
devices to
> P.C. motherboards and medical devices. I am nervous that the
ultrasonic's
> may cause damage to some of the components on the PCB of affect the
overall
> life-span and long term reliability of the product.
> Q1. Are these concerns justified ?
> Q2. Is there anyone else cleaning side 2 of PCB's which are already
built on
> side 1 using an ultrasonic system ?
> Q3. Have there been any studies carried out on the effects of
ultrasonics on
> discrete components, IC's, Tantalum Capacitors, Diodes, Transistors
or
> Co-Axial Resonators ?
>
> Option 2 - Spray Wash System
> I have also been looking at what types of Industrial Spray cleaning
systems
> are available. Are spray washing systems effective for the removal
of solder
> paste and glue from via holes and plated through holes ? How
successful is
> this type of system for cleaning misprinted intrusive reflow PCB's.
Most of
> these systems use a water based cleaning agent in the washing cycle.
This
> cleaning agent then needs to be rinsed off the PCB's before the
board can be
> built through the rest of the process.
> Q1. Is anyone out there familiar with this type of system ?
> Q2. How is the rinse water treated / filtered before it goes to
drain ?
> Q3. Are there any problems with the cleaning agent contaminating the
water
> going to drain ?
>
>
>
> Martin Bourke
>
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