Hi Eric,
I agree the interest is at ambient, or maybe the end use temperature, but the thermal excursions associated with assembly produce irreversible changes in the material. At time temperate this organic epoxy system does not return the to original properties. I just wanted to know if you change the elasticity based on how many "high thermal excursions" the board was to have experienced in theory.
Best regards,
Paul
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Thursday, August 14, 2008 8:34 AM
To: [log in to unmask]
Subject: Re: [TN] Elasticity
Paul,
Maybe. Depends on the amount of temperature variation and the consequent change in stiffness of the board and how expensive a finite element package I had. Note Tan didn't say he interested in behaviour at reflow temperatures.
Loss tangent may be more important if Tan is interested in amplitude ratios.
Regards,
Paul Reid wrote:
> Hi Eric,
>
> In your FEM would you include changes in Young's modulus of the FR4 with each thermal excursion to 260°C?
>
> Regards,
>
> Paul
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
> Sent: Thursday, August 14, 2008 8:04 AM
> To: [log in to unmask]
> Subject: Re: [TN] Elasticity
>
> Tan,
>
> By building a finite element model of the assembly you are interested in and then carrying out the appropriate analysis on the model you can determine displacements, deflections and stresses in the assembly.
>
> After that you can make an assessment of whether or not the assembly is going to survive. Of course the assessment is the hard bit...
>
> Regards,
>
>
>
> Tan Geok Ang wrote:
>
>> We are evaluating different axis's and levels of G-vibration test with different temperatures.
>> Not CTE...
>> What is E-module?
>>
>> ________________________________
>>
>> From: Hernefjord Ingemar [mailto:[log in to unmask]]
>> Sent: Thu 8/14/2008 4:07 PM
>> To: TechNet E-Mail Forum; Tan Geok Ang
>> Subject: RE: Elasticity
>>
>>
>>
>> you mean CTE ? Or E-module ? Why do you ask and what's the issue?
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang
>> Sent: den 14 augusti 2008 03:11
>> To: [log in to unmask]
>> Subject: [TN] Elasticity
>>
>> Hi All,
>> Can the elasticity of FR4 rigid PCB and solder joints (SnPb, SAC) be definite (with value)? Thanks in advance.
>>
>> Best Regards
>> GA Tan
>>
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>
> --
> Eric Christison Msc
> Mechanical Engineer
> Consumer & Micro group
> Imaging Division
>
> STMicroelectronics (R&D) Ltd
> 33 Pinkhill
> Edinburgh EH12 7BF
> United Kingdom
>
> Tel: +44 (0)131 336 6165
> Fax: + 44 (0)131 336 6001
>
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>
--
Eric Christison Msc
Mechanical Engineer
Consumer & Micro group
Imaging Division
STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom
Tel: +44 (0)131 336 6165
Fax: + 44 (0)131 336 6001
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