Hi Inge,
This is not Manson's universal slope equation, it is more general than that. The first part is the Basquin equation for high-cycle fatigue (HCF) and the second part is the Coffin-Mansion equation for low-cycle fatigue (LCF). The problem is that neither is correct the way you wrote it.
Delta epsilon = 3.5 x sigma b/E x Nf exp-0.12 + epsilon1 exp 0.6 x Nf exp -0.6
where
Delta epsilon = elongation
sigma b = rupture tension
E = elasticity module
Nf = number of cycles to rupture
epsilon1= rupture elongation
The Basquin equation really looks like this
Delta epsilon (elastic) = sigma b/E x Nf exp b
where
sigma b= fatigue strength coefficient ≠ rupturestrength (tension)
b= fatigue strength exponent, -0.07 to -0.12
The Coffin-Manson equation really looks like this
Delta epsilon (plastic) = epsilon1 exp 0.75 x Nf exp c
where
epsilon1= ductility ≠ elongation for thin specimens like foil and wire
c= fatigue ductility exponent, -0.5 to -0.7
Keep an eye out for a column on just this topic in Global SMT & Packaging magazine in about 2 months
Werner
-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Jun 16, 2010 4:54 pm
Subject: Re: [TN] ?
Thanks Wayne.
1. No aspect on 'half moon crescent' ?
2. Have you or someone else practised Manson's universal slope equation for calculation of life expectancy of bond wires?
Delta epsilon = 3.5 x sigma b/E x Nf exp-0.12 + epsilon1 exp 0.6 x Nf exp -0.6
where
Delta epsilon = elongation
sigma b = rupture tension
E = elasticity module
Nf = number of cycles to rupture
epsilon1= rupture elongation
We used this for deciding how many cycles gold wires would withstand in a typical MIL aircraft application when the substrates were alumina and the packages Kovar. The result was som 50,000 - 100,000 cycles or 60-120 years for -55/+125C.
The question is how much one can rely on this calculation model. Anyone done similar ? Personally I thing one should only see such calculations as estimations only.
Inge
--------------------------------------------------
From: "Thayer, Wayne - IIW" <[log in to unmask]>
Sent: den 16 June 2010 20:57
To: <[log in to unmask]>
Subject: Re: [TN] ?
> Hi Inge!
>
> 5 grams per square mil average shear for gold ball bonding
> Avg - 3 x StdDev > 3 grams for 1 mil gold destructive pull test
>
> The latter is kind of vague because the wire set must be large enough to > get a good sample size and all of the loops have to have reasonable > heights and must be similar.
>
> For aluminum, we're very application-dependent, but use the Avg - 3 x > StdDev as the parameter of interest.
>
> These don't test how close to cratering we are, which is an industry-wide > issue.
>
> Visually, we are looking for a consistent rim on the ball, and a rim > height no greater than about one half of the wire diameter. For the > stitch, consistency and virtually no capillary imprint from the stitch > process on the lead/land.
>
> Wayne
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
> Sent: Wednesday, June 16, 2010 1:58 PM
> To: [log in to unmask]
> Subject: [TN] ?
>
> What standards do you use for inspection and qualification of wire bonding
> today?
> Thanks
> IInge
>
>
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