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July 1999

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Subject:
From:
Anne Ledger <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 22 Jul 1999 14:29:33 -0400
Content-Type:
text/plain
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text/plain (155 lines)
Sherry,

I visited your user's group web page, WOW, there's a whole lot of info
there.  I will be digesting it for a while.  Thanks for the heads up.

Anne Ledger
EMDS, Inc.

> -----Original Message-----
> From: Sherry Goodell [SMTP:[log in to unmask]]
> Sent: Thursday, July 22, 1999 12:40 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] HASL co-planarity
> 
> Don,
> This is my first time replying to a TN question, but here it goes.
> 
> First, there is no industry standard that I am aware of on HAL
> thickness.
> The 80-800 microinches you refer to is a common specification called
> out. I
> have been processing PWBs to this specification for 14 years and have
> never
> had a reject for solderability.
> 
> Having said that, if the panels are solderable and acceptable at that
> thickness will be dependent on the HAL process that they were run on.
> Not
> all HAL is equal. A HAL Specification Guideline is downloadable at
> http://www.tet-halco.com/main.htm.
> 
> Given that HAL is a geometrically dependent process, the geometry of a
> feature will affect the thickness results. Large features tend to be
> thinner
> than small features on the same side of the panel. This is due to
> surface
> tensions of the copper and solder and the distance of the solder to
> wet-back
> on a given feature. Smaller features should be more uniform than large
> features. With horizontal HAL, when processed at a 45° angle, QFP
> sites will
> typically be very consistent from pad to pad. Typical 25 mil pitch QFP
> sites
> have a mean around 300 microinches with a standard deviation around 50
> microinches. The larger the pads, the thinner the solder deposit will
> become.   You may also wish to visit  the site of a new group for more
> information and studies on HAL Capability.
> http://members.xoom.com/sgoodell/HUG/
> 
> For a solder thickness of 80 microinches (2.0 microns) with 6 - 12
> microinches (.0152 - 0.30 microns) of IMC, solderability should remain
> excellent during storage. It is possible to have as much as 100
> microinches
> (2.5 microns) of IMC, from some HAL processes and solderability or
> shelf
> life problems are emanate. It is true that for a solder thickness of
> 80
> microinches, without knowing the type of HAL process used, could be a
> problem. Intermetallic compounds (IMC) thickness can be minimized from
> HAL.
> Typical tin/copper IMC thickness is 6 to 12 microinches (.152 micron
> to .30
> micron) average on a Unicote® horizontal leveler. Typical vertical hot
> air
> leveling processes can exceed 100 microinches of IMC. (Ref.
> IPC-TM-928) That
> is why it is important to know what type of HAL process is being used.
> I hope this helps. If I can be of further assistance please feel free
> to
> contact me off line for details of studies and related questions.
> Sherry Goodell
> Mgr. Applications Engineering
> TET Halco, 8 Delta Drive, Londonderry, NH 03053
> phone: (603) 437-8653
> Fax:  (603) 434-4156
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Don Karp
> Sent: Wednesday, July 21, 1999 8:56 AM
> To: [log in to unmask]
> Subject: [TN] HASL co-planarity
> 
> 
> Hello All,
> 
> I've been asked a stumper (for me anyway).
> 
> Is there a specification for the co-planarity (?) of HASL across the
> board?
> My customer is concerned that thickness variations (80 microinches on
> one
> land / 800 microinches on the other land - for the same component) are
> causing tilting of his components.
> 
> I know that there are minimum thickness requirements which address
> solderability, but have not heard of the above.
> 
> Don Karp
> Trace Laboratories - Central
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Don Karp
> Sent: Wednesday, July 21, 1999 8:56 AM
> To: [log in to unmask]
> Subject: [TN] HASL co-planarity
> 
> 
> Hello All,
> 
> I've been asked a stumper (for me anyway).
> 
> Is there a specification for the co-planarity (?) of HASL across the
> board?
> My customer is concerned that thickness variations (80 microinches on
> one
> land / 800 microinches on the other land - for the same component) are
> causing tilting of his components.
> 
> I know that there are minimum thickness requirements which address
> solderability, but have not heard of the above.
> 
> Don Karp
> Trace Laboratories - Central
> 
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