In production, is there a significant difference between QFN or TQFP components other than space?

Question

When producing a run of PCBs, does it matter if I choose QFN or TQFP components? Say, I want to have 1000 boards manufactured with an Atmel AVR that is available in QFN or TQFP packages. The QFN package is of course smaller, but I have enough space on the board, so that is not an issue.

For prototypes, the TQFP is easier to handle because I could even hand-solder them, if a reflow oven and stencil is not available. But for automated production, this should't matter, or does it?

For instance: would a PCB manufacturer recommend to use QFN because they are easier to handle by the pick-and-place machines, resulting in a price cut?

The difference in component price appears to be small, too.

Answer 1

For anyone reading this down the line, there is one other major issue not yet mentioned regarding QFN vs QFP when it comes to commercial production of boards - and that is reliability.

If you have a product that deals with lots of thermal cycling or other vibrational/mechanical stress, leaded parts are the way to go. Leadless parts look neater, but don't always take up less space since there's usually a big thermal pad that you can't route signals through. If you're going to produce a thousand boards that will see a rough life (outdoors, automotive, etc), leaded parts generally last about 10x longer than leadless parts before you start to see issues with cracking solder joints, etc.

I work as a EE in oil and gas, formerly aerospace, and I swear against leadless parts in these applications for this reason.

Of course, you can always take additional measures to help even the playing field (primarily potting your leadless ICs), but this doesn't guarantee that you're giving your parts the same longevity as a leaded part. Additionally, this will typically make your leadless implementations more expensive due to the additional manufacturing steps required.

Answer 2

I recommend QFN. why?

• smaller, cheaper in mass production.
• it requires less solder ( because of small pins ) and therefore monetary efficient.
• it is soldered faster than TQFP ( using an soldering machine like that pick and place that uses solder paste and hot air) because QFT packages stick to pad because of their GND tab.
• The board will look niftier and neater :) and also more professional.

Answer 3

The BlueSky's answer isn't completely correct.

• Price: There isn't big differnce or maybe it's better to say there is no differenc. e.g. check out ATMEGA8A-MU and ATMEGA8A-AU.
• Size: Again There is no big differnce indeed. in many cases QFN is half of TQFP but this factor doesn't decrease the price of manufacturing so much. although it makes your PCB a bit compact.
• Solder and Soldering: IMO solder consumption wouldn't be significant and most probably there wouldn't be any difference in soldering QFN and TQFP. because I'm sure they just put components on PCB and soldering paste on pads.

NOW I'm sure you are asking yourself "then What's the difference between these two packages? well the big differences are in electrical characteristics. for example QFN has smaller leg's length than TQFP and this means low capacitance and in some cases it's so important. many RF ICs use these kind of packages. or QFN packages include an exposed thermal pad to improve heat transfer out of the IC (into the PCB).

Answer 4

Unless you need the heatsinking effect of the large middle ground pad, you may find the QFP easier to lay out the PCB for. A QFP provides room under the chip to put vias, possibly making fan-out easier.