Yuan,

Your message seems sound enough but I would suggest the following:

1 Get artwork and have your board supplier make the coupons for you exactly as
per your production boards.
2 Get him to apply your/his preferred resist exacly as per your production
boards.
3 When you receive them, apply the flux/paste of your choice to 4 of them
WITHOUT components and pass through solder station.
4 With other coupons, mount components and solder them again with the same
flux/paste you prefer.
5 Leave some uncleaned and clean others
6 Coat some.

This programme involves 32 coupons in total each with 4 test sites = 128 test
sites.

Stage 1 = 32 coupons = 4 to be tested
Stage 2 = 28 coupons = 4 to be tested
Stage 3 = 24 coupons = 4 to be tested
Stage 4 = 20 coupons = 4 to be tested
Stage 5 = 12 coupons = 8 to be tested ie 4 uncleaned and 4 cleaned
Stage 6 = 8 coupons   = 8 to be tested try 2 different coatings

My recommendation is to use IPC B36 coupons. At least, make sure you mount
components over the comb patterns to properly reflect your production
conditions. Then have the testing done using frequent monitoring i.e. every 1
or 2 hours. We found that makes a huge difference and you should pick up any
failure trends earlier than the full 5 or 7 day cycle suggested in IPC-TM-650.

Strongly recommend you call Doug Pauls at: [log in to unmask] he will help, I am
sure.

Graham Naisbitt


Concoat Ltd                                     Email: [log in to unmask]
Alasan House, Albany Park                       Tel:    +44 (0)1276 691100
Camberley, Surrey GU15 2PL UK           Fax:    +44 (0)1276 691227


-----Original Message-----
From:   TechNet Mail Forum  On Behalf Of [log in to unmask]
Sent:   Monday, August 18, 1997 10:32 PM
To:     [log in to unmask]
Subject:        [TECHNET] No-clean rework qualification

     Hello,

     Based on my literature research, my preliminary plans would be:

     1. Obtain SIR comb pattern coupons, run them through the assembly
     process w/o components. Use interested flux and solder wire, reflow.

     2. SIR test  OR

     1. Run the product board through the assembly process w/o components.
     Use interested flux and solder wire, reflow.

     2. Ionic test like Omagemeter

     Definitely, the second plan is simpler for us. But I am not sure it
     can work. Could someone provide some advices on a simple workable
     qualification procedure for no-clean rework?

     Another related question:

     I am aware of 2 options to make test coupons: one is to get coupons;
     the other is to get Gerber file of the test pattern and generate it on
     the product board. Which one is better?

     Appreciate any help.

     Regards,

     Yuan