Hi Shiela, after the responses you have already received, I felt
compelled to offer some balance.  First of all, "All that glitters...is
not HAL"  Although most shops can do it, not all can do it well.  In
terms of planarity and cleanliness, there is a world of difference
between a 10 yr. old Brand X verticle machine and a modern computer
controled horizontal process.  I say this with some certainty after 12
yrs of service with the largest HAL service in the world.

Some of the advantages to HAL are:
1.  Solderability.  Nothing solders like solder.
2.  It assures the solderability of the plated copper and previews
    general thermal fitness prior to component attachment.
3.  Excellent shelf life.  Better than a year in normal conditions (like
    your desk drawer)
4.  Less contaminants like Cu in the solder joint. (since Hal establishes
    the inter-metalic, you attach to solder.)
5.  Plated thru holes sure solder nice. (have we gotten rid of those
    pesky holes yet?)
some of the dis-advantages are:
1.  Planarity.  Somewhere around 6 to 8 mil pitch, it gets a bit
    difficult to control thickness. (the process is geometry dependant)

With respect to BGA's, with modern HAL equipment, they are being
processed routinely worldwide.

With respect to Cleanliness, <3 mg. cl. sq. in. is routine on modern
equipment.

With respect to warping, with proper pre-heat and solder temp, minimal
warpage is produced beyond that which is authored by circuit design.
(like no thermal relief in power or ground planes)

In this cost driven, yield intensive biz, there is still a big roll for
HAL. It is not suitable for certain high density designs.  This however,
still represents only a very small portion of assembled product.

Hope this Helps,

Mark Simmons

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################