>>> lckang <[log in to unmask]> 09/18/01 08:07PM >>>
Hi Grant,
Thanks for you reply, so if you define it, how to describe? and can you suggest some feasible measure methods for it?
Best Regards,
Liu Changkang
*******
>>>> Ryan Grant <[log in to unmask]> 09/18/01 01:51PM >>>
>
>Hi Liu,
>The definition for coplanarity comes from Geometric Dimensioning and
>Tolerancing definitions and exist to prevent confusion. You are mostly
>correct in your interpretation, but be careful about re-defining coplanarity
>into something more simple because that may cause confusion under different
>circumstances.
>
>For example, how do you define the lowest lead? On a four sided QFP, each
>four sides will have a single lead that is lower than all the others on that
>particular row. However, that lowest lead on one side may never touch the
>"established seating plane" and therefore can not be considered the lowest
>lead.
>
>Furthermore, suppose one of the rows has all of the leads perfectly in line
>with each other, but the entire row is excessively bent. That row would be
>the first to contact the "established seating plane" and become the lowest
>lead, even though it would appear that row did not have the lowest lead.
>
>From a practical standpoint. We just want to know if all the leads will sit
>in solder when placed on a board.
>
>Kind Regards
>
>Ryan Grant
>Advanced Technology Engineer
>MCMS
>(208) 898-1145
>[log in to unmask]
>
>
>> -----Original Message-----
>> From: Jack Crawford [SMTP:[log in to unmask]]
>> Sent: Tuesday, September 18, 2001 10:41 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Question about Coplanarity
>>
>> >>> lckang <[log in to unmask]> 09/17/01 08:48PM >>>
>>
>> Hi Technetters!
>> According to JESD22-B108 (complanarity test for SMD), the device's
>> coplanarity defined as the largest distance distance between the contact
>> point of leads and the established seating plane, but when the
>> estabilished seating plane is estabilished by three leads which are bend
>> downwards, Is it mean that all other device leads are out of planar
>> position.
>> So can I define it as vertical distance measured from the lowest
>> lead?
>> Thanks for your any input.
>>
>> Best Regards,
>> Liu Changkang
>>
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