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Lead coplanarity is a measurement of the
distance between the highest and lowest lead when the connector is sitting
on a perfectly flat surface. Coplanarity of leads is critical for good
solder fillets. Ideally, all leads should lie in the same plane because
if even one lead is significantly higher or lower than the plane, it could
lead to open solder joints. Most specifications call for coplanarity to
be a maximum of 0.004 inch (0,10
mm) to .008 inch (0,20mm) deviation from the seating plane. For practical
purposes, this means that the distance between the highest and lowest
lead cannot exceed this amount. Coplanarity is a difficult and time consuming
measurement. However, due to the critical nature of this specification,
and the difficulty in maintaining it, it is very important that it be
controlled through statistical sampling and quality assurance procedures.
Laser measurement equipment accurate to within .000001 inch (0,000025mm)
is available and can be employed for this purpose.
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