PCB Assembly Services - Screaming Circuits: QFN / QFP switcheroo


QFN / QFP switcheroo

Here's an all too familiar face. We see this a lot with chips that have both a QFP (quad flat pack)and a QFN (quad flat pack, no leads) package. Especially if the QFP packaged part has been around for a long time and the QFN version is fairly new.

Qfp_qfn_4 In the CAD package, the two components look pretty close. You have a center flag pad and lots of leads. Unless you have the component sitting right there with you, it's not always easy to tell at a glance that you have selected the wrong package. A quick give-away though is the length of the leads. If you have long lands for the leads like this footprint, it's a good bet that you have a QFP library part. I won't guarantee it, but it's likely enough that you should conduct some further investigation to make sure you won't end up with sad boards like these.

The reverse is true too. If your actual component is a QFP and the land pattern has very short leads, you should look closer.

Duane Benson
Quirky perhaps Mr Longfellow


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