Currently we are designing a board thicker than normal with small
     holes.

     The board is a 10 layer board, 082" thick, and uses 13.5 mil
     drilled/plated holes.

     The board is large ~ 13 x 16" in size.  It is HASL.  During component
     assembly it will see 2 IR processes and a  wave.  We are specifying
     the board as IPC Class 2.  It will be used in high end computer
     product.  Reliability is very important.

     In light of the above I have several questions for this distinguished
     group:

     1.  Considering the 6 to 1 aspect ratio, using conventional FR-4 will
     the design above have reliable plated through holes?

     2.  We are considering specifying that the FR-4 be of Tg greater than
     170 Deg C.  The hope is that this will improve hole relaibility.  The
     problem is that this will add significant cost to the board.  Is it
     necessary to do this?

     3.  The design is dense so that we cannot grow the hole significantly.
     We are considering permitting hole breakout of 1 mil, so that the
     holes can be drilled larger.  Is this a reliability risk?

     4.  Are there other alternatives (not so expensive) to improve hole
     reliability?

     I would appreciate any feedback.

     Thanks,

     [log in to unmask]

################################################################
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
################################################################