My 3 cents:
#3 Splitted replenishing: just by two dosing pumps instead of one.It is much
more easier than calibrating of valves.
Another questions: providing the etching is set at optimal conditions and
there is no need for rework-why beginning of dry film lifting in replenisher
rinse is bothering you?The copper is not etched in this section!!!
The lifting of photoresist resulting attack on lines is in the etching
section.
Edward 

Edward Szpruch
Eltek , Manager of Process Engineering
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9395050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]

> -----Original Message-----
> From: Robert Welch [SMTP:[log in to unmask]]
> Sent: ב מרץ 19 2001 22:38
> To:   [log in to unmask]
> Subject:      Re: [TN] Dry Film Breakdown In Ammoiacal Etching
> 
> Larry,
>  
> With what sounds like 4' of etcher and 6' of replenisher rinse in an
> alkaline etcher you are going to have problems keeping keeping resist from
> falling off.
> #1.     Right idea. I f possible vent most of the excess ammonia from
> between the replenisher and etch chambers.
> #2.    You should be pretty close to optimum speed right where you're at,
> providing the chlorides are staying up.
> #3.     Great idea in theory but I've never been able to master the
> mechanics of controlling a split replenisher feed for any long period of
> time.
> #4.     Forget the first part. Much to complicated and probably would not
> help.  Controlling dragout of COMPLEXER is the main purpose of the
> replenisher rinse.
>  
> Points to remember:
> A.    The ammonia GAS is what attacks the resist, not pH alone.  You
> develop it in an aqueous carbonate solution of around 10.5 pH.  Be sure
> the resist remains flooded as much as possible in the replenisher chamber
> to help protect it from the GAS.  Even so try to get your pH down closer
> to a 8.1 steady state.
> B.     About 2'-3' of cascaded replenisher rinse with good squeegee
> rollers between each chamber is all you should need to minimize complexer
> dragout.  
> C.     I would utilize the extra space as a dragout/isolation chamber with
> the drippings going back to the replenisher.  The exhaust air needs to be
> moving back toward the etch chamber to remove the ammonia from the resist
> surface.
> I've engineered a lot of these systems over the years but always ended up
> moving something and or cutting something. 
> Good Luck
>  
>  
>  
> 
>       -----Original Message-----
>       From: TechNet [mailto:[log in to unmask]]On Behalf Of Larry J. Fisher
>       Sent: Sunday, March 18, 2001 8:32 PM
>       To: [log in to unmask]
>       Subject: [TN] Dry Film Breakdown In Ammoiacal Etching
> 	
> 	
>       I am hoping someone can give me some guidance to help solve a dry
> film 
>       breakdown issue in ammoniacal etching. The dry film(s) seem to be
> processed 
>       perfectly normally (optimum conditions) through the developing step.
> An 
>       overview of the etching consists of: 
> 	
>       1. Main etching chamber, with vent 
> 	
>       2. Cascading replenishing section about 50% longer than the main
> etch 
>       chamber, with vent (either closed or only barely open). Fresh
> etchant fed 
>       into the replenishing section, then cascading into the main etch
> chamber. 
> 	
>       3. Ammoniacal etchant  in main chamber at 124 deg F and pH of 8.2 to
> 8.3. 
> 	
>       4. Copper level at about 22-23 ounces/gallon 
> 	
>       5. Main etchant controlled by specific gravity at 1.21. 
> 	
>       6. pH of fresh etchant - 9.9 
> 	
>       7. pH of cascading etchant feeding into the main chamber (after
> traveling 
>       thorough the cascading replenisihing section) - 9.3-9.5 
> 	
>       8. Etching spray pressured - Approx 35 psi 
> 	
>       9. Dwell time in main etch chamber - 45-50 seconds 
> 	
>       10. Dwell time in replenishing section - 60-75 seconds 
> 	
>       Through these etching conditions, there can be dry film lifting
> along the 
>       circuit traces and/or broken tents. After consulting the literature
> and 
>       talking to a few experts, my thoughts on how to correct these
> problems 
>       consist of: 
> 	
>       1. Increase the venting in the replenishing section so that the pH
> of etchant 
>       coming into the main chamber will be lowered to about 9.0 and this
> will also 
>       reduce the amount of ammonia fumes in the replenishing section. 
> 	
>       2. Lower the copper content a little, increase the temperature a
> little 
>       and/or lower the specific gravity a little so that the etch rate
> will 
>       increase and the panels will go through faster and the dwell time in
> the main 
>       chamber/replenisher will be lower. 
> 	
>       3. Set up a "Y" connection from the fresh etchant so that some goes
> into the 
>       main chamber and some into the replenishing section. This will
> maintain pH in 
>       the main etch chamber and allow the ammonia/pH in the replenishing
> section to 
>       go down. 
> 	
>       4. Feed fresh etchant only into the main etch chamber. Install fresh
> etchant 
>       into the replenishing section and change out once per week. Use
> squeegee 
>       rollers in the replenishing section to prevent "drag out" of copper
> into the 
>       fresh rinse section (after replenishing section). 
> 	
>       Do you think I am on the right track here, or am I "all wet". Also,
> do you 
>       have any other ideas that may help me out here. I would appreciate
> any input 
>       from all you capable "TechNetters". 
> 	
>       Regards, 
> 	
>       Larry Fisher 
> 	
>       Allen Woods & Associates 
> 	
> 	
>       4. 
> 

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