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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