Manish,
1, Try talking to some wafer saw manufacturers. Disco and Kulicke & Soffa
are the major ones. They make the machines and will know the current
practices used by their customers. K&S have a web page. Disco probably do
too.
2, Die are picked up from the sticky tape using either vacuum tips that
contact the top surface, vacuum collets that engage on the edges, or clamps
that pick up two edges. Before being picked up needles are pushed up under
the tape to peel the back of the die from the tape. Sometimes the tape is
penetrated, sometimes not. Collets are not used much as a different one
needs to be made for each die size, also damage to the corners of the die
is possible. Vacuum tips that touch the top surface are made either with a
hard plastic, or metal, or a soft rubber. The soft rubber is more prone to
picking up debris that can be pressed into each die surface, damaging each
device. Hard plastic, or metal can work well if the push up of the die from
the tape and the contact with the tip is well controlled and gentle. Edge
contact by grippers is probably the ideal, but is mechanically more
complicated. This is a good method for things like area array flip chips.
3, Top side damage is the obvious risk, see above, but back side, edge
and corner damage is also possible. The needles can put microcracks in the
die that can grow under stress. This is one reason for using rounded
needles to push up the die that don't pierce the tape. Damage to the edges
and corners of die by the sawing operation, flexing of the sawn wafer on
tape, or impact damage with the edges of waffle packs can also give chip
outs and microcracks that can grow under stress. This is particularly a
concern with flip chip devices, where the silicon can be under high stress.
4, When I was involved in this work over three years ago control was by
periodic inspection. The risk was low, but if problems occured it could
destroy large numbers of parts. I don't know if anyone has come up with a
better method since.
regards, Jeremy Drake
Celestica Ltd.
Stoke on Trent
England
---------------------- Forwarded by Jeremy J Drake/HQ/CUK/Celestica on
20/10/98 08:13 ---------------------------
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to Manish <[log in to unmask]>
To: [log in to unmask]
cc: (bcc: Jeremy J Drake/HQ/CUK/Celestica)
Subject: [TN] Reg: Dicing operations
Hello everybody
I would appreciate if somebody could please help me with the following:
1.0 where could i find information about the wafre dicing practices used
in the industry.
2.0 After the dicing opration is completed, the dice are placed in the
waffle packs. What kind of pick up tips are used to transfer the dice
from the wafer to the waffle packs.
3.0 Would the transferring of the dice from the wafer to the waffle pack
introduce damage to the top side or the back side of the dice.
4.0 What are the current practices used in the industry in order to check
those damages. In other words hw does one assure a defect free prodcut to
the customer.
Knowing the above is kind of urgent for me. Therefore,
Any help in this regard would be greatly appreciated.
Regards
Manish
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