I find a stencil to be almost mandatory, with solder paste, if the number of components starts to become high, or multiple PCBs need to be assembled.
You spend a little time for prep (align the stencil correctly), but then you lay paste pretty quickly.
You spend a little time for prep (align the stencil correctly), but then you lay paste pretty quickly.
AIM65,
The board arrived today! Thanks Very Much!
My goodness those small devices are indeed "SMALL" lol!!!
I will have to get that hot air gun for sure...
Alex
The board arrived today! Thanks Very Much!
My goodness those small devices are indeed "SMALL" lol!!!
I will have to get that hot air gun for sure...
Alex
AIM65, in post #37, are you stating to use solder paste, apply with a syringe, then heat from behind or the back side of the board with the eyelet feed thru?
1. Place solder paste across pins and the heat sink area under the chip.
2. Carefully place small part on board, stays put from the solder paste.
3. Heat from backside of board and allow time for the entire to get hot enough for the solder paste to work its magic.
This method no hot air gun is needed.
I think this might work well?
Alex
1. Place solder paste across pins and the heat sink area under the chip.
2. Carefully place small part on board, stays put from the solder paste.
3. Heat from backside of board and allow time for the entire to get hot enough for the solder paste to work its magic.
This method no hot air gun is needed.
I think this might work well?
Alex
Hi Alex,
8 days for standard letter, it's not so bad.
Yes, its roughly the method used with the 3 chips in VSON/WSON packages, but with slight differences :
- Step 1 : Solder paste is applied (not much, see EEVBLOG video in post#29) component side only across pins and the thermal pad under the chip
- Step 2 : Ok
- Step3 : Soldering iron temperature was 450°. Tip used was big and with a large flat surface (see picture). Fresh solder was applied on tip before applying tip on board (backside) for thermal transfer. Parallelism between tip surface and board surface is key for thermal transfer.
- Step 4 : Excess of melted solder component side is removed with solder wick, with the edge of the wick, not the side, in order to clean the spaces between the pins of the chips.
On picture, example of tip used for this operation: left one; right one may be used for smd resistors, caps and SOIC packages: OPA1642
Chris
Attachments
Thanks Chris.
I will print out the schematic, layout pix and BOM today and get the order into Mouser and or Farnell etc...
Still thinking of a hot air gun as well, but I know this method will work with your design.
What case did you use, size?
Alex
I will print out the schematic, layout pix and BOM today and get the order into Mouser and or Farnell etc...
Still thinking of a hot air gun as well, but I know this method will work with your design.
What case did you use, size?
Alex
Some parts are Farnell distributor brands : Multicomp and Prosignal, They should be available only at Farnell.
PCB has been designed for a particular box I found on ebay, very cheap one !. This is an Italian shop but it's shipped from asia.
DIY Aluminum PCB Box Enclosure Electronic Project Case 100*76*35mm | eBay
Chris
Alex,
I did use 10uF for all.
C24 is used for a time constant at power up, quality doesn't matter
C17 and C23 are located close the OPA1622 for PSU decoupling, those are good quality, low ESR caps.
Chris C7 in the schematic is a 2200uf electrolytic, 25 volt. in the bom its this:
Rubycon 25ZLG100MEFC6.3X11 1281812 which is for a 100uf cap? Is this an error in the BOM?
Alex
Rubycon 25ZLG100MEFC6.3X11 1281812 which is for a 100uf cap? Is this an error in the BOM?
Alex
Alex,
You're right, sorry for this. I've used 100uF Rubycon ZLG in another project, and I've picked up the wrong reference in my order list history.
The right cap reference is for a Rubycon miniature cap, PK serie, ref : 25PK2200MG412.5X20. Farnell ref : 234651.
Chris
NP,
FOund most of the stuff, having an issue with the Farnell only switches, they have them but the US store points to the UK store and states its only stocked in the UK and its an additional $20 charge to each part!!
So I am looking at Mouser and digikey for the switches etc..
Alex
FOund most of the stuff, having an issue with the Farnell only switches, they have them but the US store points to the UK store and states its only stocked in the UK and its an additional $20 charge to each part!!
So I am looking at Mouser and digikey for the switches etc..
Alex
To clarify I spoke to Farnell and they add only $20 to an order for parts stocked in the UK. So its not for each part, phew!!
They have all the switches etc..yeah!
One of the electrolytics, the three 10uf they are backordered until July, but they had a suggested replacement.
I found a case on ebay from the west coast USA for $8.16 shipped, its on its way!
Have to finish the bom for the resistors and order.,
Alex
Still have to get solder paste, solder wick and a hot air gun (just in case)
They have all the switches etc..yeah!
One of the electrolytics, the three 10uf they are backordered until July, but they had a suggested replacement.
I found a case on ebay from the west coast USA for $8.16 shipped, its on its way!
Have to finish the bom for the resistors and order.,
Alex
Still have to get solder paste, solder wick and a hot air gun (just in case)
Hello Alex,
I should spend more time on QA ! 😱
About the switch, having the three position ‘Low Xfeed’, ‘No Xfeed’ and ‘High Xfeed’ is not mandatory. With only 2 positions ‘Xfeed’ / ‘No Xfeed’ you could use a DPDT ON-ON switch rather than the DPDT ON-OFF-ON one. You should easily found a DPDT ON-ON subminiature switch with the same footprint and pinout as the Multicomp one, thus saving $20. If you do so, remove R7 and R9 in order to have the ‘No Xfeed’ position.
For the paste and flux I’ve used following products I’m happy with :
Paste: low temperature, with lead
EDSYN CR44, ref Farnell: 876768
Flux: Gel, No Clean, for leaded solder
Chipquick SMD291, ref Farnell: 1850216
EDSYN CR44, ref Farnell: 876768
Flux: Gel, No Clean, for leaded solder
Chipquick SMD291, ref Farnell: 1850216
Updated BOM is attached
Chris
Thanks again for the information...
Back again to the micro soldering job at hand!! You indicate to use a "small" amount of solder paste. Did you use the dispenser the solder paste came in from Farnell or us an actual syringe...I guess I am asking is the dispenser small enough to put a "very small" amount on these tiny pads?
Alex
Back again to the micro soldering job at hand!! You indicate to use a "small" amount of solder paste. Did you use the dispenser the solder paste came in from Farnell or us an actual syringe...I guess I am asking is the dispenser small enough to put a "very small" amount on these tiny pads?
Alex
I have used the dispenser shipped with the syringe and a spare one (ref farnell 876800). "Small" amount means a bit less than showed in the EEVblog video. Small dispenser (<0.8mm) provide the right amount of paste, too small require too much pressure on the piston.
To evaluate/understand the behavior of the paste and the amount required, I have practiced by soldering smd resistor with the paste.
OK, thanks. I changed the value but not the ref during the tests. Both values are ok. They set 7805 output to 5.4V/5.5V.
I'll update BOM to 18 Ohms. Consider using SFR16S0001809JA500, Farnell: 9475702