We have a long history of singulation methods. We make a range of very small
high density modules in assembly arrays on very thin BT substrates, and have
gone through these hoops:
V-cut is cheapest, but accuracy is poor both vertically and horizontally,
components have to be too far from the edge and so waste board real estate,
and the rough edges with fibre protrusion cause problems in handling,
delamination and probably moisture absorption. Boards also have to be
rectangular and that's not always possible.
Routing board edges and leaving mouse bites within the array fix some of
these problems but create others. The main one is the stress caused by
manual breakout. Thin boards can flex and that causes stress on chip
components and their solder joints. In high volume this is also more than a
little tedious and therefore expensive. V-cut singulation within a routed
array has worked but has the same problems as above but to a lesser extent -
you can use a blade with a vertical adge on one side and an angled edge
facing the route cut, so you can get components a little closer to the board
edge, but accuracy and tolerances still cause problems.
We looked at die punch, and that would be a perfect solution for our high
volumes except that BT laminates are brittle and don't punch at all well.
Edges are rough, there were signs of delamination, and the tooling
maintenance is expensive - dies need to be very sharp and glass reinforced
BT is murder on sharp edges, from what we were told.
We also looked at using an IC dicing saw. That would have been a great
solution, as the blade is very thin leaving little waste and the accuracy is
excellent. Unfortunately, it's an expensive machine and our assembly house
wanted us to foot the bill and pay for maintenance. We decided that was a
little risky and chose to forgo that path because alternatives were also
available. It is also restricted to rectangular boards.
Our current method works best. That's a combination of major routing inside
the array during fab, leaving the corners of the board unrouted, and then
singulating at the corners with a router after assembly. That minimises the
amount of routing required post assembly, gives us the accuracy and board
edge finish we want, allows us to have non-rectangular boards, and is an
automatic process suitable for high volumes with the right fixtures and
tooling. Most importantly, it doesn't stress the components and allows me to
have components closer to the board edge, reducing wasted real estate.
That's for what we do. I would imagine bigger, thicker boards with less
density and lower volumes can live with some of the restrictions of V-cut
and mousebites and so would be easier to singulate. Not all assembly houses
have post-assembly routers.
Andy Kowalewski
SyChip Inc
Phone (02) 9456 7984
[log in to unmask]
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Brooks,Bill
Sent: Saturday, 2 July 2005 08:20
To: [log in to unmask]
Subject: [DC] De-paneling or Singulation of boards from an assembly panel
I am currently reviewing an old board we have that has issues with
separation from the assembly panel... I would like to know what methods of
'singulation' you have tried and the measure of success you had with it...
I think many of us have encountered issues with assembly panel designs and
might be able to share the things that do and don't work with us...
Types of panels I am familiar with...
Routed edge with tabs
Tabs with mouse or rat bites
v-scoring
die punch and return
cracker boards
Which methods do you prefer and why?
Which methods to you avoid and why?
Bill Brooks -
----------------------------------------------------------------------------
-----
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV
1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET
DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
----------------------------------------------------------------------------
-----
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------
|
