Part Number: PCF8574
Hope you are well and enjoying the holidays. Please see below customer question
We want to optimize the paste mask for : PCF8574RGTR (VQFN package) The datasheet states: "84% printed solder coverage by area under package" Questions specifically for exposed die pad: Is this the recommended paste mask coverage pre-assembly? If so; what is the allowable void area post assembly? Is this per IPC specification?
Randhir S Kalsi
Technical Sales Associate
In reply to Bobby Nguyen:
I wasn't able to find too much on this matter however this is what I found:
"Is this the recommended paste mask coverage pre-assembly?"
-This is the recommended coverage by TI.
"Is this per IPC specification?"
I only have access to the IPC-7525a standard (there seems to be a later revision denoted by the letter b) which seems to indicate the minimum and maximum area of solder paste to be 50% to 80% of the exposed pad. From this, I would recommend the customer use the 80% number as it aligns closer to our recommended number and also fits the standard.
"what is the allowable void area post assembly?"
I wasn't able to find anything on this but our device will still work in the case where parts of the pad aren't completely covered by solder. This will just affect the thermal dissipation of the device.
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