3 ms·

It worked for me 8 times :) Thankfully the bottom pad on DFN packages reach the edge on 2 sides and I would think this technique wouldn't work with QFN.

by granra 2y ago

dragontamer 2y ago
QFN is (very, very slowly) opening up to the idea of "wettable flanks", which is increasing the reliability of QFN soldering anyway... which is increasing the opportunity of "side-soldering" QFN packages. https://www.ti.com/document-viewer/lit/html/SSZTBN6 https://www.ti.com/document-viewer/lit/html/SSZTBN6 Here's to hoping for more manual soldering techniques to work into the future! We all know that these parts are getting extremely small and harder to work with, but its still clearly possible to make devices. But yeah, QFNs, if this wettable-flank trend continues, could be quite reliably soldered and inspected from the sides soon. The needs of the high-reliability automotive industry to create an inspection methodology outside of X-Rays is driving this change. ------------ Glad to hear that your technique worked in any case. I wouldn't have tried that, but maybe I'll try it once next time I have a hot-air gun out and a DFN part to try it on. EDIT: Note that Microchip apparently has some DFNs that also have wettable-flanks: https://www.microchip.com/en-us/about/media-center/blog/2022/dfn-packages-with-wettable-flanks https://www.microchip.com/en-us/about/media-center/blog/2022...
- jamesy0ung 2y ago
  That's very interesting, I've always found QFN to be annoying to work with
- OJFord 2y ago
  > The needs of the high-reliability automotive industry to create an inspection methodology outside of X-Rays is driving this change. Why is that a particular requirement? Or is it just nobody wants/rather avoid x-ray, and automotive has greater need for inspection at all?
  - cinntaile 2y ago
    It's probably cost? X-ray is an expensive technique.
    - OJFord 2y ago
      Yeah but that's not specific to automotive right, that's what I meant. I was trying to understand whether they meant the need for inspection or the non-X-ray was the particular concern in the automotive industry.
  - cpgxiii 2y ago
    Automotive has much higher reliability requirements than consumer devices, and since solder failures are probably the leading cause of failures using *FN parts, they want to have effective inspection methods to ensure devices are assembled properly. When you use parts with leads, you can easily perform all of your QA checks using machine vision (all all the components in the right place, are they correctly aligned, are the connections properly soldered, etc), but if you use parts with no leads and the solder connections are hidden, you need a separate X-ray check which takes additional time, assembly-line space, and money. Depending on the components in question, it may also be tricky to get enough contrast in the X-ray image to identify defects.
metadat 2y ago
To save others from looking up DFN / QFN: DFN -> Dual-flat no-leads package QFN -> Quad-flat no-leads package https://en.wikipedia.org/wiki/Flat_no-leads_package https://en.wikipedia.org/wiki/Flat_no-leads_package
- dragontamer 2y ago
  The important note is: 1. Longer leads of older packaging have higher parasitic inductance, parasitic capacitance, and parasitic resistance. Which hurts many electronic designs. 2. The thermal pad on DFN / QFNs allows for direct-heat transfer off of the chip-package (while DIP, SOIC, and other older designs do NOT allow for this direct-heat transfer off). This improves thermals of hot parts, as you can use the whole PCB as a heatsink now, instead of having to add a heatsink elsewhere. 3. DFN and QFN are physically much smaller than traditional DIP, SOIC or TQFP packages. So people who use these smaller chip packages can make even smaller circuit boards, or alternatively, a more complex design fit in smaller spaces. ------- QFN and DFN are very popular parts for modern professional level electronics. But do note that their small size and tiny leads make them harder to deal with at the hobbyist level. But its possible with enough flux, solder paste, and hot-air rework to work with these parts. I would recommend that beginner electronics who are just getting into custom PCB design work with larger parts (like SOIC packages) instead. Bigger is often easier. Move to these tiny DFN or QFN parts only after you've gained confidence in your surface-mount skills.
  - amelius 2y ago
    Any tips for handling BGA packages? Is it possible for hobbyists?
    - dragontamer 2y ago
      I've never used a BGA unfortunately. My understanding is that BGA solder-balls come pre-attached to your chips in most cases. As long as you reflow-solder it on correctly on the 1st try, you're good. If you need to "fix" BGA, that's where things become very difficult for hobbyists. To do this, you need to unsolder the BGA with hot-air, lift it off, then "Reball" the BGA, which is equipment that likely hobbyists don't have. ------------ With regards to QFN or DFN vs BGA, I would expect BGA to be easier, as long as you've precisely made your soldermask to accept the correct sized solder-balls (which should be part of your chip's documentation). That is: BGA's hardest part is getting the board design just right. Especially because most BGAs require 4 or more layers before you can route all of the lines to them. In fact, the massive BGAs are physically impossible on anything less than 8 layer boards. ------------- Hobbyists won't have XRay equipment to see if the BGAs successfully worked either. So rework and quality-control are basically impossible. Your only hope is to "do it blind" and hope for the best. Which... is fine? Even BGA parts are relatively cheap. So build 3+ of your design at once. Have appropriate test-probes to take measurements during the "smoke test", and bam, you're good. One of those three tries is probably going to be successful.

It worked for me 8 times :) Thankfully the bottom pad on DFN packages reach the edge on 2 sides and I would think this technique wouldn't work with QFN.

by granra 2y ago

It worked for me 8 times :) Thankfully the bottom pad on DFN packages reach the edge on 2 sides and I would think this technique wouldn't work with QFN.

dragontamer 2y ago

QFN is (very, very slowly) opening up to the idea of "wettable flanks", which is increasing the reliability of QFN soldering anyway... which is increasing the opportunity of "side-soldering" QFN packages. https://www.ti.com/document-viewer/lit/html/SSZTBN6 https://www.ti.com/document-viewer/lit/html/SSZTBN6 Here's to hoping for more manual soldering techniques to work into the future! We all know that these parts are getting extremely small and harder to work with, but its still clearly possible to make devices. But yeah, QFNs, if this wettable-flank trend continues, could be quite reliably soldered and inspected from the sides soon. The needs of the high-reliability automotive industry to create an inspection methodology outside of X-Rays is driving this change. ------------ Glad to hear that your technique worked in any case. I wouldn't have tried that, but maybe I'll try it once next time I have a hot-air gun out and a DFN part to try it on. EDIT: Note that Microchip apparently has some DFNs that also have wettable-flanks: https://www.microchip.com/en-us/about/media-center/blog/2022/dfn-packages-with-wettable-flanks https://www.microchip.com/en-us/about/media-center/blog/2022...

jamesy0ung 2y ago
That's very interesting, I've always found QFN to be annoying to work with
OJFord 2y ago
> The needs of the high-reliability automotive industry to create an inspection methodology outside of X-Rays is driving this change. Why is that a particular requirement? Or is it just nobody wants/rather avoid x-ray, and automotive has greater need for inspection at all?
- cinntaile 2y ago
  It's probably cost? X-ray is an expensive technique.
  - OJFord 2y ago
    Yeah but that's not specific to automotive right, that's what I meant. I was trying to understand whether they meant the need for inspection or the non-X-ray was the particular concern in the automotive industry.
- cpgxiii 2y ago
  Automotive has much higher reliability requirements than consumer devices, and since solder failures are probably the leading cause of failures using *FN parts, they want to have effective inspection methods to ensure devices are assembled properly. When you use parts with leads, you can easily perform all of your QA checks using machine vision (all all the components in the right place, are they correctly aligned, are the connections properly soldered, etc), but if you use parts with no leads and the solder connections are hidden, you need a separate X-ray check which takes additional time, assembly-line space, and money. Depending on the components in question, it may also be tricky to get enough contrast in the X-ray image to identify defects.

metadat 2y ago

To save others from looking up DFN / QFN: DFN -> Dual-flat no-leads package QFN -> Quad-flat no-leads package https://en.wikipedia.org/wiki/Flat_no-leads_package https://en.wikipedia.org/wiki/Flat_no-leads_package

dragontamer 2y ago
The important note is: 1. Longer leads of older packaging have higher parasitic inductance, parasitic capacitance, and parasitic resistance. Which hurts many electronic designs. 2. The thermal pad on DFN / QFNs allows for direct-heat transfer off of the chip-package (while DIP, SOIC, and other older designs do NOT allow for this direct-heat transfer off). This improves thermals of hot parts, as you can use the whole PCB as a heatsink now, instead of having to add a heatsink elsewhere. 3. DFN and QFN are physically much smaller than traditional DIP, SOIC or TQFP packages. So people who use these smaller chip packages can make even smaller circuit boards, or alternatively, a more complex design fit in smaller spaces. ------- QFN and DFN are very popular parts for modern professional level electronics. But do note that their small size and tiny leads make them harder to deal with at the hobbyist level. But its possible with enough flux, solder paste, and hot-air rework to work with these parts. I would recommend that beginner electronics who are just getting into custom PCB design work with larger parts (like SOIC packages) instead. Bigger is often easier. Move to these tiny DFN or QFN parts only after you've gained confidence in your surface-mount skills.
- amelius 2y ago
  Any tips for handling BGA packages? Is it possible for hobbyists?
  - dragontamer 2y ago
    I've never used a BGA unfortunately. My understanding is that BGA solder-balls come pre-attached to your chips in most cases. As long as you reflow-solder it on correctly on the 1st try, you're good. If you need to "fix" BGA, that's where things become very difficult for hobbyists. To do this, you need to unsolder the BGA with hot-air, lift it off, then "Reball" the BGA, which is equipment that likely hobbyists don't have. ------------ With regards to QFN or DFN vs BGA, I would expect BGA to be easier, as long as you've precisely made your soldermask to accept the correct sized solder-balls (which should be part of your chip's documentation). That is: BGA's hardest part is getting the board design just right. Especially because most BGAs require 4 or more layers before you can route all of the lines to them. In fact, the massive BGAs are physically impossible on anything less than 8 layer boards. ------------- Hobbyists won't have XRay equipment to see if the BGAs successfully worked either. So rework and quality-control are basically impossible. Your only hope is to "do it blind" and hope for the best. Which... is fine? Even BGA parts are relatively cheap. So build 3+ of your design at once. Have appropriate test-probes to take measurements during the "smoke test", and bam, you're good. One of those three tries is probably going to be successful.