Alan:								
		Just a quick clarification note. Sodium napthalene acts as a 
surface treatment to remove the fluorine atom from the FEP molecular chain. 
This allows the surface to wet and become bondable. For high bond strength 
and reliability this step is required whether there is smear or not. Sodium 
napthalene will not remove drill smear.					
						regards			
						     Michael Barmuta	
						     Staff Engineer	
						     Fluke Electronics Corp.	
						     Everett Wa.	
						     425-356-6076  

On Thu, 1 May 1997 19:28:10 -0700 ALAN COCHRANE wrote:

> From: ALAN COCHRANE <[log in to unmask]>
> Date: Thu, 1 May 1997 19:28:10 -0700
> Subject: Re: FAB: IPC-HF-318 and Teflon Smear
> To: [log in to unmask]
> 
>      Andy,
>      
>      You may want to look at the time the drill is in the hole.  Excessive 
>      time in the hole may cause the FEP to become very plyable and cause 
>      smear.  I don't know how much FEP(thickness) is in the stack-up in 
>      typical applications the amount is very thin(<.003).  You will likely 
>      have to go through a sodium napthalyene etch if you are not able to 
>      prevent the smear initially.
>      
>      Regards,
>      
>      Alan B. Cochrane
>      Director of New Technology
>      Multek Inc.
>      
> 
> 
> ______________________________ Reply Separator 
_________________________________
> Subject: FAB: IPC-HF-318 and Teflon Smear
> Author:  [log in to unmask] at INTERNET_GATEWAY
> Date:    5/1/97 2:38 PM
> 
> 
>      I have a multilayer RF PWB application, using Rogers' Duroid 6002, 
>      procured to IPC-HF-318.  FEP film is being used as the bond film, 1/2 
>      ounce copper is used on the innerlayers.  The part is used in a 
>      high-reliability application.
>      
>      The problem is that a large percentage of product is being failed at 
>      microsection due to excessive smear.  IPC-HF-318 allows up to 25% 
>      smear along the vertical interconnect at the T-Joint.  We regularly 
>      see T-Joints with up to 50% and 75% smear.  Not all holes in all 
>      sections have this much smear, but if it happens in one hole, the 
>      entire panel is rejected.
>      
>      RF tests show that, regardless of the amount of smear seen in the 
>      cross-section, the boards are electrically (RF) acceptable.  Also, 
>      we've performed thermal cycle testing which indicated no degradation 
>      in RF performance.
>      
>      SEM micrographs of "as drilled" holes confirm that the smear is due to 
>      the drill operation.  Two sets of drill studies have been performed, 
>      with only marginal improvement.  The smear is not removed when 
>      subjected to plasma cleaning.  
>      
>      My questions include:
>      - Is this amount of smear unusual?  If it's not, should IPC-HF-318 (or 
>      its successor) be changed?
>      - Have others seen it before?
>      - Is this another quirk of 6002?
>      - Was IPC-HF-318 written for 1 ounce copper, therefore implying that 
>      .00035 inches of smear (25% of 1 ounce copper) is really acceptable?
>      - Is there any embraced reliability data that may indicate it is not a 
>      reliability problem?
>      
>      I would appreciate any help in either reducing the problem (smear) or 
>      in determining that IPC-HF-318 is not the appropriate criteria to be 
>      used in accepting/rejecting this condition.
>      
>      
>      Andy Pedersen
>      Harris Corp.
>      [log in to unmask]
>      407-729-2143
>      
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