Well spoken, Syed!
The AOI will only provide process control over the gold wire routing, the bond placement location, and can detect missing bonds or damaged bondwires and variation in studbump or ball size. But it does that very well. Here at GD we perform AOI on various devices and standard assemblies using a MVP. At one of the other clients I work for, there are many wirebonders and diebonders and there we manufacture literally millions of components, and that is where we are using AOI as a method of process control for bond routings, hybrid assembly, BGA assembly and ball attach, and other technologies. The AOI is a great method for inspecting for ball size and presence and spacing, as well as for wirebond presence, routing, bump ball size, and location away from adjacent conductors, just prior to encapsulation.
Pull testing is performed on a sample basis for strength of wirebonds. Shear testing is performed for solderball and microcomponent attachment process control.
The MVP AOI is used in all of these processes. I strongly recommend you contact a MVP sales rep and discuss with them what you want it to do. More than likely, you can find several other things to check with the AOI. I even use it for epoxy staking inspection. In the past I also used it for connector pin inspection, where all of the pins needed to be located a certain distance from both a local reference point, but also with respect to each other. I was able to pretend the top of each pin was an 00105 chip, and the machine found 100% of any pins out of position. As far as I know, the MVP is the only AOI that has programmable focus in the Z-axis, but I could be wrong about that.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ahmad, Syed
Sent: Thursday, April 24, 2014 8:42 AM
To: [log in to unmask]
Subject: Re: [TN] Wire-bonding AOI

AOI will only tell the correct placement of a wire bond.
In the semiconductor packaging world, the degradation of the Au-Al bond is measured in a number of ways. 
Mechanically, it is measured by pulling the wire or by shearing the Au-Al joint. 
The results of the wire pull test are given in the form of the pull strength in gf (gram-force) values and the corresponding failure modes. 
In a wire pull test, when the wire fails in the mid span, the only thing it tells is that the gold ball bonds to the aluminum bonding pads on the die and to the bonding pads on the substrate or leadframe are stronger than the wire itself. As-made unstressed bonds made using an optimized ball bonding process are expected to fail at mid-span as the gold ball bond area to the bonding pad on the chip is twice or larger than the cross sectional area of the wire itself. Failure at other locations may only occur if the process is not set up properly.
If the failure is at the neck of the bond to the die or the substrate or frame, again it does not provide much insight into the condition of the Au-Al bond and just indicates weakness at the neck of the ball bond or at the neck of the stitch bond. Reasons for such failures have been studied extensively over the years.
The only time the pull test provides information about the Au-Al interface is when the Au-Al bond lifts off the aluminum bonding pad on the chip. What it means is that either it was an un-optimized bond to begin with, or the Au-Al bond had deteriorated to the extent that its interfacial area or strength had been reduced significantly. 
Additionally, mechanical testing is destructive. 
The ball shear test can cause failure through Au or Al metals, can rip silicon out from under the Al, or shear through the intermetallic eliciting the weakest part of the structure. This test again is destructive though it is more useful than the wire pull test in determining the condition of the Au-Al interface.
Electrically, the health of the joint is looked at by measuring resistance changes in the interconnect. As the Au-Al interface degrades, the resistance of the bond increases. This method is non-destructive and can be used for monitoring the Au-Al bond continuously.
The initial resistance and later changes in the Au-Al wire bonds are influenced by more than one factor. 
The quality of initial bond affects the resistance of the interconnect.
The form of the interaction area depends upon the process. The amount of interaction area also influences the resistance of the bond.
The shape of the interaction area affects the way the intermetallics and voids will progress at the bond site.
After the bond has been made, changes in resistance are affected by the gradual formation of the intermetallics, their by-products and their interaction with materials present in its surroundings. 
Various intermetallics have different rates of formation and differ in their resistivity and strength until they reach an equilibrium.
The diffusion of the metals occurs at their interfaces.
The intermetallic formation process also generates Kinkendall voids. These voids contribute to changes in the resistance of the interconnect. 
Intermetallics and voids formation is also affected by the gases present in the environment depending on the level of their access to the system. 
The gases affecting the intermetallic and void rates can come from the environment of an un-encapsulated bond. 
The sources of gaseous elements are also provided by the encapsulant materials around the bonds. 
When the gases are entering from the sides of interface, the void proliferation tends to spread laterally.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Thursday, April 24, 2014 6:09 AM
To: [log in to unmask]
Subject: [TN] Fw: [TN] Wire-bonding AOI

"All professional skills are mastered by critiqued practice" - by Schon.
  Original Message
From: Joyce Koo <[log in to unmask]>
Sent: Wednesday, April 23, 2014 11:14 PM
To: Stadem, Richard D.
Subject: Re: [TN] Wire-bonding AOI


There are developing process regarding the wire bonding. Usually, you do ball size inspection for consistency, ball share for initial strength, aging and wet chemical etch plus cross section for intermetallic coverage and thickness (depend upon the die metallization and thickness, composition of both your wire and pads). Table tear usually good enough for second bond strength, the modern machine will automatically identify "no stick". Wire loop is based on visual, with current state of the art bonds per device reach to 1000 or more and multi-teir stack type, aoi? With speed of bonder, very difficult. As for process monitoring, bond 15 at every 4 hour interval, and do wire pull (stitch peel) and ball shear, will be the same guide after a fully developed process. (or you can ask for 5 bonds per direction, just in case you have problem optimize different travel directions). My 1.8 cents.

"All professional skills are mastered by critiqued practice" - by Schon.
  Original Message
From: Stadem, Richard D.
Sent: Wednesday, April 23, 2014 5:27 PM
To: TechNet E-Mail Forum; Joyce Koo
Subject: RE: [TN] Wire-bonding AOI


IMC is pull-tested on a sample basis. Bondwire routing and location is 100% machine inspected (AOI). You use the correct combination of sampling and visual inspection to ensure that both the wire routing is correct, and the bond meets the strength requirement.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Wednesday, April 23, 2014 12:46 PM
To: [log in to unmask]
Subject: Re: [TN] Wire-bonding AOI

Why you need that? For al or Au? It is self testing by the bonder, if I am missed something.‎ Besides, you always need to do imc. Inspection, aoi is not good enough. (can't see imc) .

"All professional skills are mastered by critiqued practice" - by Schon.
  Original Message
From: Ioan TEMPEA
Sent: Wednesday, April 23, 2014 11:46 AM
To: [log in to unmask]
Reply To: TechNet E-Mail Forum
Subject: [TN] Wire-bonding AOI


Dear Technos,

I need info regarding AOI machines with wire bonding inspection capability. Efficiency of the technology, suppliers, price tags, table top vs. inline, personal experiences, can they also do regular SMT AOI, anything you can tell me, on-line or off-line.

Any particular experience with this one? http://www.viscom.com/asia/products/wire-bond-inspection-aoi/s6053bo-vs6056bo-inline-aoi/

Thanks,

Ioan Tempea, P. Eng.
Manufacturing Engineer
Satellite Systems
MDA
21025 TransCanada Highway
Ste-Anne-de-Bellevue, Qc, Canada H9X 3R2
Tel: +1-514-457-2150-3556
www.mdacorporation.com<http://www.mdacorporation.com>

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