Tape Automated Bonding (TAB)
by Peter Lagner, Advantest (Europe) GmbH
01 Oct 04
TAB technology had its first boom in the early seventies. After that it has been overtaken by wire bonding as a general chip interconnect technology. Today TAB is well introduced in Japan and Taiwan and it features many benefits in applications like LCD drivers, high speed circuits, high pin count circuits or very low profile designs.1
What is TAB ?
Tape Automated Bonding is an interconnect technology between the substrate and the IC, using a prefabricated carrier with copper leads adapted to the IC pads instead of single wires.
This prefabricated carrier, usually a tape consists of a perforated polyamide film, like a camera film, and of the same dimensions, which has a transport perforation and stamped openings for the IC and the connection leads.
On this film is then glued a copper foil, and its copper is structured by photolithography like a flexible circuit. The advantage of this process is the creation of free standing fingers in the tape openings, which are then soldered or welded to bumps previously created on IC pads (Inner lead bonding). The mounted IC can be burned-in, tested, and afterwards punched out from the tape.
No mechanical protection is needed contrary to the COB Technology, the bumps sealing hermetically the IC, and he leads showing a mechanical strength of about ten times the strength of a bonded wire.
Why TAB ?
TAB was originally invented as a quick and robust alternative to the wire bonding technology. In the early days of wire bonding this process was manual and very slow.
In the meantime, Wirebonders became automatic, free programmable and very rapid, and the initial advantages of TAB vanished at a level that this technology was mainly abandoned. Only Japanese and
Taiwanese manufacturers continued with this interconnect technology for consumer products as calculators, cameras and watches. They consequently improved the process of automatic handling for large
quantities and the advantages in miniaturization There is a Japanese expression created : "Keihakutansho" meaning "light, thin, short, strong"
Why TAB is coming again ?
IC’s went through an impressive history of miniaturization, as device densities have increased several orders of magnitude. A direct consequence is a proportional increase of the I/O count. This continuing trend of higher pin count and smaller equipment sizes pushes the move towards smaller packages. TAB has an important advantage against COB in the way that pad sizes on the IC can be reduced more than a factor two for TAB. LCD drivers take consequently this advantage for their big number of I/O’s
Who may need TAB ?
The formerly mentioned properties scanned already some applications where TAB may be considered as an interesting interconnection alternative:
LCD Drivers are probably best suited for TAB, combining all the assets needed :
- Flat profile (Chip Thickness plus 60µm)
- High pin-count (18 – 250 I/O)
- Lowest Pad Pitch (actually down to 60µm)
- Automatic assembly (very high quantities)
- Flexible substrate (direct attach to the LCD)
Optical Encoders need a minimum distance between the optical system and the chip surface. The very robust TAB interconnection, the flat profile and the hermetic sealing give TAB many advantages.
Miniaturized Systems, as hearing aids, are easily realized with TAB, taking benefit from the combination of elements on a flexible substrate and the possibility of 3-dimensional mountings.
What is a TAB Handler ?
The M7521A TAB handler, is a handler which can simultaneously measure a maximum of four TAB (Tape Automated Bonding) and COF (Chip on Film) packaged devices. With the introduction of the M7521A, Advantest will enter the tape and film package testing market, adding to its line-up of high-function IC handlers for use with other types of packages, including those for memory and SoC (System on Chip) devices.
Demand for FPD’s (Flat Panel Displays) including liquid crystal displays (LCDs) and plasma display panels (PDPs), is growing rapidly given the increasing popularity of large televisions and handheld information devices and phones. The FPD market in 2003 was around 2.5 times over the previous year market. As the picture quality of displays improves, driver ICs are becoming both more miniaturized and integrated. As a result, conventional TAB packages and even thinner COF packages are expected to come into greater use.
The new M7521A is a handler that can simultaneously measure four fine-pitch thin-film mounted driver ICs at a high speed (0.9sec/4PF). Moreover, the handler is compatible with a two-row configuration for a single roll. This results in an expansion of the tape design area and makes fitting equipment into space easier. In addition, the handler is installed with high-precision image recognition equipment, allowing for highly accurate alignment with the test system portion and facilitating reliable contact even with fine-pitch terminals.
The M7521A also has a reel map function that makes it possible to collect package quality results such as "good," "defective level 1," and "defective level 2," which are detected by the test system, for each package. The tabulation of this reel map information makes it possible to immediately investigate results of quality judgements. This, in turn, makes it possible to decide whether to re-test or further analyze the cause of inferior products for improving production yield of packages.
M7521A TAB Handler
- Compatible Tape: TAB, COF (35 mm/48 mm/70 mm. Wide-type and super-wide type.)
- Reel: Maximum diameter of 620 mm Punch Part: Maximum of two (compatible option)
1 Edgar Weise, Microbonding SA,Noiraigue