Linear Pump for Underfills
John Baliga, Associate Editor -- Semiconductor International, 5/1/1999
Microelectronic Packaging Inc. (MPI, San Diego,
Calif.) announced that it has been selected by Litel (San Diego,
Calif.) to provide development and manufacturing services for high-density
interconnect microelectronic assembly.
Intel (Santa Clara, Calif.) recently announced its
Easy BGA CSP for its Fast Boot Block flash memory. It is 10X13 mm, with an
8X8 mm, 1.0 mm pitch pinout.
Johnson Matthey Electronics (JME, Eden Prairie, Minn.) and Thermacore International Inc.
(Lancaster, Pa.) signed an agreement to combine expertise in thermal
management and allow for joint marketing and sales. The agreement
complements one JME signed with Flomerics Inc. (Surrey, UK) in June
1998.
Texas Instruments (TI, Dallas, Texas) selected
Sheldahl's (Northfield, Minn.) ViaThin tape ball grid array (TBGA)
substrates for its Cavity-Down Star BGA ASIC packages. Initial designs are
to have 352 to 600 leads.
Fujitsu Limited (Tokyo, Japan) and Fujitsu
Microelectronics, Inc. (FMI, San Jose, Calif.) received a U.S. patent
for various types of BGA packaging technology. The original filing date of
this patent was September 22, 1980.
Hyundai Electronics Industries Co., Ltd.
(HEI, Ichon, Korea) and its U.S. subsidiary
Hyundai Electronics America (HEA) have agreed to sell a 90% interest in
Hyundai's ChipPAC business to a U.S. investor group led by existing
ChipPAC management. ChipPAC also announced availability of its EconoCSP
packages for mobile applications.
ASAT (Hong Kong) placed an order for Model 8020
automatic wire bonders and Model 7500 plus dicing systems from Kulicke
& Soffa Industries (Willow Grove, Pa.) valued at nearly $4
million.
Electroglas (Santa Clara, Calif.) signed a volume
purchase agreement with Tower Semiconductor (Migdal Haemek, Israel)
for multiple Horizon 4090 automatic wafer probing systems with SORTnet
network communications and data management.
A symtek
recently introduced a pump that can dispense programmable amounts of typical
packaging fluids with better than 1% (3s)
weight accuracy for shot sizes from 30 to 305 mg. The company developed the
DP-3000 series linear pumps for its automated dispensing equipment.
Company News
The servo controlled pump is a true positive displacement pump that is not affected by fluid viscosity, supply pressure, needle size or temperature of the fluid or pump. Shot size programming is not only simpler for a given material, but it is independent of the material. This makes the pump a 'plug and play' item. In a manufacturing setting, this can reduce the number of spares that need to be kept on hand.
The company also designed it with 'quick release' mechanisms to simplify changeout procedures. The number of wetted parts was also minimized to simplify cleaning and to minimize priming requirements and waste.
At least one other company, MRSI (Chelmsford, Mass.), has announced the use of a linear positive displacement pump. The Dual-LPD is said to have better than 1% dispense accuracy, as well as a design that simplifies changeout and removal for cleaning.
It has a dual chamber design to enable continuous dispensing. Instead of
waiting for the chamber to refill between shots, the nozzle can switch to the
second chamber while the first one fills. This is also useful for large volume
dispense applications, where one part requires more material than one chamber
can hold.
Anisotropic Conductivity?
A number of researchers recently proposed the use of anisotropically conductive adhesives (ACAs) for flip-chip applications instead of bumps and underfills. The materials are conductive in one direction, but insulating in the other two. It would simply be applied on the bonding area, and the die would be placed on top.
Electrical connections between the die and substrate would occur due to the conductivity in the vertical direction, but the material would not short adjacent connections. What is essentially a die bonding operation would replace bumping, attaching and underfilling.
ACAs are really die bonding adhesives with a relatively small number of large conductive particles of uniform size. The bond force is chosen so that the particles determine the bondline thickness. The particle size and bond pad pitch are chosen so that there is a high probability that at least one particle will be trapped by each bond pad pair and a low probability that the particles would line up to short two connections.
Researchers at Loctite's Dublin, Ireland facility presented their work on ACAs at Nepcon West in February. They plan to magnetically order particles in the materials to ensure a uniform distribution of particles, which would enhance the desired probabilities.
Processes using ACAs would be simpler than typical flip-chip processes having
fewer steps. Reliability of flip-chip interconnection often depends on the
ball's size and the ball/pad interface's quality. The applications for ACAs will
likely be limited to lower performance and lower thermal stress applications.
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