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  • TI Thinks Resolved

PCF8574: Optimize the paste mask

Part Number: PCF8574

Hello team,

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?

Regards,

Randhir

Randhir S Kalsi

Technical Sales Associate

  • Hey Randhir,

    Unfortunately, this is not a question I am familiar with and most of my senior members on my team are on vacation.

    I expect they will be back on Tuesday so I can get you an answer sometime that day.

    Sorry for the wait,
    -Bobby
  • In reply to TRX Bobby:

    Hey Randhir,

    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.

    Thanks,

    -Bobby

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