Posted by Guest: Sun Jun 22, 2003 11:01 pm    Post subject: Resolving Ball Lifting Issues

I am a new wirebond engineer who's encountering a lot of ball lifting issues lately. What advice can you give me on how to resolve ball lifting issues?

Thanks,
Wbeng

Posted by Guest: Sun Jun 22, 2003 11:03 pm    Post subject:

Hello Wbeng,

Welcome to the Assembly forum!

Don't worry - most new WB engineers get their baptism of fire from ball lifting. Here are things that you need to look for: 1) anomalies in the set-up of the wirebond equipment - parameter settings, mechanical stability, etc.; 2) anomalies on the bond pad: bond pad contamination, bond pad corrosion, excessive and/or multiple probe marks, topography imperfections; 3) anomalies in the bonding itself: misplaced bond.

Before suspecting any other cause, you must establish that there is nothing wrong with your set-up. Equipment problems would usually manifest in the ball bond formation itself, i.e., you may see signs of: size abnormality, insufficient or excessive aspect ratio (ball too high or ball too flat, respectively), or excessive non-symmetry of the ball.

Once you're sure that the equipment/set-up is OK, you may suspect that something on the bond pad is interfering with the proper formation of ball bond intermetallics. Usually this 'something' is a contaminant. Note that contaminants on bond pads are not always visible, so don't conclude immediately that the bond pad is clean if it looks clean. For example, an unetched layer of glass on the bond pad may look invisible to you, so you need to do some compositional or elemental analysis on the bond pad (usually EDX analysis) before writing up your report.

Ball lifting encompasses a wide range of manufacturing issues that can not be covered completely in this response. The good news is that ball lifting is a fairly well-understood mechanism already, and there are hundreds of engineers out there who can add to this thread to help you.

Good luck!

-EE

Posted by Guest: Sun Jun 05, 2005 5:58 am    Post subject:

i am new in this forum... and i really want to learn so many things about wire bonding.. well, specially now that we are encountering lots of problem with wire bond process... i am really thankful for knowing this site... i hope somebody who's very well equiped with knowledge about wire bond process could help me resolve some of my problems with regards to wirebond process... i may not be suited with my career but i want to prove myself that i can, just like men, also function as well as them... and here goes my first question:

if ball bond lifting is caused by those factors stated by EE, how can we prevent or at least minimize this during wire bonding?

Posted by Assy Engr 3: Mon Jun 06, 2005 9:13 pm    Post subject:

Hi guest, what name can we call you? If you are a new engr, try to learn from the assembly experts in your area. If you have no experts and your managers are relying on you, then you need to do the following immediately:
1) do literature research on wirebonding from books, the internet, etc; try to get a copy of George Harman's book and read it over and over again;
2) build an FMEA for your wirebond station: ------/fmea.htm
3) attend seminars like asemep
4) post your questions in forums like this.

Assy Engr 3

Posted by Guest: Mon Jun 06, 2005 11:38 pm    Post subject:

ooopss...sorry... i forgot to put my name under my message... thank you very much with your suggestion.. i really appreciate it... actually i am not an engineer in our area...i am just a technician but i oftenly encountered this problem in our line and i feel that it is a major problem in the line...can you just imagine a yield which is just almost 20% per shift? and sometimes zero as in 0% yield at all?!.... i always received criticisms from my boyfriend with this problem cause he too is a technician but not in our area and they do not have this kind of of problem (to be specific yield problem..)and of the last meeting that we had had with our engineers they stated that lifted ball is the major problem causing yield issue in us...