Magnet Wire Failing In PinHole Test

Dear Peter & Spectre07,

Thanks a ton for your suggestions. My point wise reply as under:

A) Get the oven cleaned up as Spectre07 suggested you do.- Done

Make sure the wire is properly centered in the oven and make sure the wire does not touch any part of the oven. - Done

C) Make sure that the surface of the wire is of very high quality. – Surface is of good quality. Not excellent. Meaning thereby at 60 x magnification we can see some marks on the surface probably due to slippage in drawing machine. But the same is not visible at normal 10 x magnification levels and the wire also feels absolutely smooth when touched.

D) Get the oven ventilation back into a standard configuration. – Done. The first zones temperature of 350 deg C was not achieved so we are in the process of adding more heaters. We intend to run the machine at 350/400/450 configuration for the three zones. Hopefully with first zone at 350 should be high enough for the evaporation of the solvents.

E) Get the annealer quench tank water temperature up to 190F and keep it there. Currently it is at 75 degrees. We are trying to get it up to 190F /85C. One question though the conductivity of the water changes with temperature. We have been advised to keep the conductivity below 50 microsiemens. We are trying to keep it below 30. However this level is checked after allowing the water to cool down to around 40C and not at 80C. Also the pH in the quenching bath is being maintained at 7-8.5 pH and for this the inlet water to the quenching bath is maintained at 6 pH. Is this OK?

F) Make sure all other components of your oven are working properly. – Done. Checked by using the ampere rating and reading of all heaters.

G) Wipe the wire before the annealer to eliminate loose copper fines. Done. Double wipes before and after annealer.

H) Hold very tight control over all of your process and let us know in about a year how you made out managing this intermittent problem. – Will Do.
Peter, We are already an ISO 9001 approved organization and have started cpk measurement for some CTQ parameters as a part of Six Sigma drive. However, we are not able to pin-point the cause of this problem despite our best efforts.

Also on the point raised by Richard regarding high speed of enamels. Here in India the problem is reverse. Since most of the machines are having vxd around 15 the enamels are suited for these machines. For very high vxd machines (above 100 ) there have been reports that the enamels available locally are not able of matching up.

I appreciate your help and definitely do not expect problem solving from behind a desk. However, would want to know from both of you on the basis of what has been discussed so far do you think in your opinion that the problem could possibly be due to solvent trapping??

Thanks and regards,

RM

Hi...as per my knowledge lower thermal rated wire typically run at faster speeds then higher thermal rated wire - when they have about the same percentage of solids. Urethanes run faster than modified polyesters which run faster than polyester which runs faster than ML. Throw in an overcoat and you change things again.  All this has its dependency on the pcb design and its material. So carefully choose the pcb manufacturer and i always recommend to choose pcb turnkey assembly service as it makes the job easier and saves a lot of time.