I really hate auto correct, that should have said creep. I corrected it.
Pat Goodyear Retired Control Tech. PG&E
Sent from my iPad
> On Apr 18, 2016, at 9:42 PM, pat goodyear <[log in to unmask]> wrote:
>
> Well I'm going to throw in my two cents here. These are the types of failure modes I have dealt with for 30+ years, usually it is the combination of stress by restricting the pin and temperature causing the motive force. One thing to keep in mind is that solder is not a solid, it is plastic and will respond to physical forces, Gravity, temperature, and so forth, keep in mind the board is moving not the pin. I have see edge mounted boards that have had components fall off due to solder migration, or creep.
>
Pat Goodyear Retired Control Tech. PG&E
> Sent from my iPad
>
>> On Apr 18, 2016, at 5:28 PM, George Wenger <[log in to unmask]> wrote:
>>
>> Ricardo,
>>
>> What is the case metal or what is it's CTE? My suggestion is to do XRF measurements of the gold thickness on the connector lead as well as EPd and ImmAg thickness measurements on the PCB as well as a cross section through the temperature cycled solder joint.
>>
>> What is your primary concern? Are you just interested in the reason for why you see the movement and the appearance of the solder joint? Or are you afraid that you might actually see solder joint failures in field use?
>>
>> George
>>
>> ----- Original Message -----
>>
>> From: "Ricardo Moncaglieri" <[log in to unmask]>
>> To: [log in to unmask]
>> Sent: Monday, April 18, 2016 5:57:43 PM
>> Subject: Re: [TN] Solder Cracking After Thermal Cicling
>>
>> Steve,
>> Responding your question.
>>
>> Soldered connection is not put under vibration during temp cicling.
>>
>> This terminal belongs to a connector which is screwed on a case and its
>> terminal passes through this metalic case and lyies on the pcb ENEPIG
>> pad.
>> So that there are following CTEs playing and intercating each other all
>> together:
>>
>> PCB CTE
>> Solder CTE
>> Case CTE where is screwed the conector
>> Terminal CTE
>>
>> brgds,Ricardo
>>
>>>>> Steve Gregory <[log in to unmask]> 18/04/2016 18:47 >>>
>> Hi Ricardo,
>>
>> I finally have your pictures up, they are here:
>>
>> http://stevezeva.homestead.com/A15_Photos_of_pre__post_100_temp_cycling_CSC-10_SN12.pdf
>>
>> Boy, that looks like a big CTE mis-match. A question; are the boards
>> going
>> through ESS? Vibration along with the temp cycling?
>>
>> Steve
>>
>> On Mon, Apr 18, 2016 at 2:35 PM, Ricardo Moncaglieri <
>> [log in to unmask]> wrote:
>>
>>> Steve,
>>> Attached arethe pictures.
>>> Thank you a lot.
>>> Await for your comments.
>>> brgds,Ricardo
>>>
>>>>>> Steve Gregory <[log in to unmask]> 18/04/2016 15:22 >>>
>>> Hi Ricardo,
>>>
>>> The Technet server strips the attachments, send your photo directly
>> to me
>>> and I'll get it posted...
>>>
>>> Steve
>>>
>>> On Mon, Apr 18, 2016 at 11:43 AM, Ricardo Moncaglieri <
>>> [log in to unmask]> wrote:
>>>
>>>> Dear colleagues;
>>>>
>>>> Steve Gregory, could you please upload the enclosed picture?
>>>>
>>>> Solder become perturbated / cracked after thermal cicling:
>>>>
>>>> This picture corresponds to a plane (not circular) conector
>> terminal
>>>> solded to a pcb pad ENEPIG finished.
>>>> The connector terminal has been gold removed by twice pretin.
>>>> Solder used is Sn63Pb37.
>>>> Thermal cicling: 50°C to 125°C
>>>>
>>>> As picture showed there are stretch marks toward left direction
>> and
>>>> showed solder crack.
>>>>
>>>> Our provider reported temperature didnt pass over 125°C and solder
>> used
>>>> 63/37.
>>>>
>>>> Question:
>>>>
>>>> How could these kind of gooves or stretch marks have been produced
>>>> taking into account they are just toward one direction (left) and
>> of
>>>> considerable length?
>>>> Just mecanic stress?
>>>> Temperature overpassing on any cicle?
>>>> Need of use of different alloy, ie.: In, Bi etc?
>>>> Provider reported the process is being useed from them since long
>> ago
>>>> (same solder alloy, temperature, pcb, terminal conector, thermal
>>>> cicling) but this is the first time they faced with such a
>> cracking.
>>>>
>>>> Do you have any comment in order to anlyse/solve this trouble.
>>>>
>>>> Appreciate your feedback we are in middle of a providing
>> acceptance
>>>> tests space quality level (IPC class 3).
>>>>
>>>> brgds,Ricardo
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