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Soldering a LQFP 48 on a home made PCB

Soldering a LQFP 48 on a home made PCB

2014-11-07 by Phil Quinton

Hi,

I've been lurking around here for some time and decided it was about time I asked a few questions myself :)

I've managed to get consistent single sided PCB's using Press n Peel, a GMC laminator and ferric chloride. However, when it comes to soldering LQFP's, I've been using pre-made LQFP to DIP adapters ( pre-tinned ). I've started to do small SMD resistors and capacitors, but I'd like some advice on the easiest way to solder LQFP's.

Every video I've found, the pads are already tinned.. Based on my own experience, if I attempt to tin the pads with solder by hand, I'll make a pigs ear of it.

I'm interested in how you guys do it?

Thanks in advance,
Phil.



Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by James

Put some gel flux (or liquid, but I prefer gel/paste from a syringe) down on the bare pads which you have previously cleaned with whatever solvent you prefer, align the IC, solder down  a pin on one corner to tack it in place, then just drag along the pins with your iron that has been pre-loaded with some solder, or you might prefer to "stroke" away from the pins, or use iron and solder together.  

Any bridges are usually easily sucked away by a cleaned iron, or wick if necessary.

The key is adding that extra flux.

Also, make the pads longer than whatever your PCB design tool's standard footprint is, even just 0.2mm extra length will make it easier to get solder on and wipe away bridges.


On Fri, Nov 7, 2014 at 8:40 PM, Phil Quinton phil.quinton@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
 

Hi,

I've been lurking around here for some time and decided it was about time I asked a few questions myself :)

I've managed to get consistent single sided PCB's using Press n Peel, a GMC laminator and ferric chloride. However, when it comes to soldering LQFP's, I've been using pre-made LQFP to DIP adapters ( pre-tinned ). I've started to do small SMD resistors and capacitors, but I'd like some advice on the easiest way to solder LQFP's.

Every video I've found, the pads are already tinned.. Based on my own experience, if I attempt to tin the pads with solder by hand, I'll make a pigs ear of it.

I'm interested in how you guys do it?

Thanks in advance,
Phil.




Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by Phil Quinton

James,

Thanks for the reply.

Do I need to keep the flux just on the pads ( appears fiddly ), or can I just apply to the whole of the pads as a "square" of flux?

Am I correct in thinking that the latter would end up with more solder bridges due to the solder flowing between the pins due to the flux being between the pins?

Thanks,

Phil.

On 07/11/14 07:47, James bitsyboffin@... [Homebrew_PCBs] wrote:
 
Put some gel flux (or liquid, but I prefer gel/paste from a syringe) down on the bare pads which you have previously cleaned with whatever solvent you prefer, align the IC, solder down  a pin on one corner to tack it in place, then just drag along the pins with your iron that has been pre-loaded with some solder, or you might prefer to "stroke" away from the pins, or use iron and solder together.  

Any bridges are usually easily sucked away by a cleaned iron, or wick if necessary.

The key is adding that extra flux.

Also, make the pads longer than whatever your PCB design tool's standard footprint is, even just 0.2mm extra length will make it easier to get solder on and wipe away bridges.


On Fri, Nov 7, 2014 at 8:40 PM, Phil Quinton phil.quinton@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
 

Hi,

I've been lurking around here for some time and decided it was about time I asked a few questions myself :)

I've managed to get consistent single sided PCB's using Press n Peel, a GMC laminator and ferric chloride. However, when it comes to soldering LQFP's, I've been using pre-made LQFP to DIP adapters ( pre-tinned ). I've started to do small SMD resistors and capacitors, but I'd like some advice on the easiest way to solder LQFP's.

Every video I've found, the pads are already tinned.. Based on my own experience, if I attempt to tin the pads with solder by hand, I'll make a pigs ear of it.

I'm interested in how you guys do it?

Thanks in advance,
Phil.





Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by James

Just spread the flux all over, no need to do it individual pads.

The flux will help prevent solder bridges, not create them, copper that is fluxed will more readily suck up the solder.




On Fri, Nov 7, 2014 at 9:12 PM, Phil Quinton phil.quinton@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
 

James,

Thanks for the reply.

Do I need to keep the flux just on the pads ( appears fiddly ), or can I just apply to the whole of the pads as a "square" of flux?

Am I correct in thinking that the latter would end up with more solder bridges due to the solder flowing between the pins due to the flux being between the pins?

Thanks,

Phil.

On 07/11/14 07:47, James bitsyboffin@... [Homebrew_PCBs] wrote:
 
Put some gel flux (or liquid, but I prefer gel/paste from a syringe) down on the bare pads which you have previously cleaned with whatever solvent you prefer, align the IC, solder down  a pin on one corner to tack it in place, then just drag along the pins with your iron that has been pre-loaded with some solder, or you might prefer to "stroke" away from the pins, or use iron and solder together.  

Any bridges are usually easily sucked away by a cleaned iron, or wick if necessary.

The key is adding that extra flux.

Also, make the pads longer than whatever your PCB design tool's standard footprint is, even just 0.2mm extra length will make it easier to get solder on and wipe away bridges.


On Fri, Nov 7, 2014 at 8:40 PM, Phil Quinton phil.quinton@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
 

Hi,

I've been lurking around here for some time and decided it was about time I asked a few questions myself :)

I've managed to get consistent single sided PCB's using Press n Peel, a GMC laminator and ferric chloride. However, when it comes to soldering LQFP's, I've been using pre-made LQFP to DIP adapters ( pre-tinned ). I've started to do small SMD resistors and capacitors, but I'd like some advice on the easiest way to solder LQFP's.

Every video I've found, the pads are already tinned.. Based on my own experience, if I attempt to tin the pads with solder by hand, I'll make a pigs ear of it.

I'm interested in how you guys do it?

Thanks in advance,
Phil.






Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by Dylan Smith

I find that it makes no difference and trying to apply to the pads only is a frustrating waste of time.
I just use a flux pen and draw over all the pads.

I also use kapton tape to hold the IC down for soldering rather than trying to tack corners down. You can stick the tape to the top of the IC and hold the tape to align and once the pins are nicely all on their pads, press the tape down onto the PCB. Then just drag solder the two exposed sides, remove the tape, and solder the remaining two sides.

On 07/11/2014 09:12, Phil Quinton phil.quinton@... [Homebrew_PCBs] wrote:
James,

Thanks for the reply.

Do I need to keep the flux just on the pads ( appears fiddly ), or can I just apply to the whole of the pads as a "square" of flux?

Am I correct in thinking that the latter would end up with more solder bridges due to the solder flowing between the pins due to the flux being between the pins?


Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by Dwayne Reid

The problem with all of the suggestions made so far is that everyone is assuming that the pads already have solder on them.

But this is a brand-new home-made board with bare copper pads.

The first step is to tin all of the pads.  Use lots of flux - gel or paste flux works best but standard liquid flux will also work.  Flood all of the pads with solder, then apply more liquid flux on top of the solder blobs.  Hold the board vertically with the pads vertical, then use a soldering iron to draw the solder down to the ends of the pads and on to the tip.  Rotate the board 90 degrees and repeat until all of the pads are tinned and cleaned.  The pads should now have a thin, smooth layer of solder on top of the copper.

Do a very good inspection with magnification to ensure that you don't have any solder bridges.  Then follow the (excellent) advice already given.

Hope this helps!

dwayne

PS - we used to make hundreds and hundreds of our own PCB's in the early days of our business.  We would clean the boards mechanically with a fine-grit sander followed by a 3-step chemical cleaning process.  Blow the boards dry with warm air from a vacuum-cleaner motor, then feed the boards through a GBC laminater (modified for lower temperature and higher speed) loaded up with Dupont Riston dry-laminate film.  Exposed the boards with a modified mercury-vapor expose lamp and vacuum frame, then developed the exposed boards with a soda-ash (potassium carbonate?) solution.  Stripped the remaining laminate in a caustic-soda (sodium hydroxide) bath, rinsed, then etched in an Ammonium Persulphate bubble etch tank.

The whole process worked very well but it just took too much time.  We eventually went to CNC milling for PCB prototypes (several years), then quit that and just started using APC for prototype boards.  All of our production boards are now made in China - the quality is extremely high and the cost is astonishingly low.  APC still does our prototype boards.

dwayne


At 02:29 AM 11/7/2014, Dylan Smith dyls@... [Homebrew_PCBs] wrote:

I find that it makes no difference and trying to apply to the pads only is a frustrating waste of time.
I just use a flux pen and draw over all the pads.

I also use kapton tape to hold the IC down for soldering rather than trying to tack corners down. You can stick the tape to the top of the IC and hold the tape to align and once the pins are nicely all on their pads, press the tape down onto the PCB. Then just drag solder the two exposed sides, remove the tape, and solder the remaining two sides.

On 07/11/2014 09:12, Phil Quinton phil.quinton@... [Homebrew_PCBs] wrote:
James,

Thanks for the reply.

Do I need to keep the flux just on the pads ( appears fiddly ), or can I just apply to the whole of the pads as a "square" of flux?

Am I correct in thinking that the latter would end up with more solder bridges due to the solder flowing between the pins due to the flux being between the pins?


--
Dwayne Reid   <dwayner@...>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
Custom Electronics Design and Manufacturing

Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by Erik Knise

Dwayne,

I too have worked on a lot of raw uncoated copper boards.  One of my customers had a board with tons of surface mount parts on it that we went through 30-40 iterations of until he got his design nailed down.  Once we got solder masked boards and were able to run them on the pick and place it was a breeze except for the few 0201 and 0402 parts I still had to hand solder.

I agree that tinning them would be a good idea but I've always soldered my prototype boards without tinning.  I found that for larger parts with lots of leads that it was almost impossible to get the tinning consistent enough to have the part lay flat on the board.   It's hard enough with an unmasked raw board getting the parts position correctly, but red neck tinning doesn't seem to work well.  Sometimes when tinning those boards you can put too much solder on the traces under the part and it won't sit flat.  The few times I had to tin, I tinned lightly with a soldering iron and then reflowed with more flux and a hot air re-work tool to get it to smooth out.

I honestly haven't had that many issues with it.  I fluxed the leads of the part and the pads on the board.  Put a blob of solder on my soldering iron and after positioning the part I tap two opposing corners to tack it down.  Works 99% of the time.  Then I drag solder everything else and clean up the tacks last.  We were using water soluble solder and liquid flux.  Haven't had as good of results with rosin core or no-clean.

--
Erik L. Knise
Seattle, WA

On Fri, Nov 7, 2014 at 8:37 AM, Dwayne Reid dwayner@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:


The problem with all of the suggestions made so far is that everyone is assuming that the pads already have solder on them.

But this is a brand-new home-made board with bare copper pads.

The first step is to tin all of the pads.  Use lots of flux - gel or paste flux works best but standard liquid flux will also work.  Flood all of the pads with solder, then apply more liquid flux on top of the solder blobs.  Hold the board vertically with the pads vertical, then use a soldering iron to draw the solder down to the ends of the pads and on to the tip.  Rotate the board 90 degrees and repeat until all of the pads are tinned and cleaned.  The pads should now have a thin, smooth layer of solder on top of the copper.

Do a very good inspection with magnification to ensure that you don't have any solder bridges.  Then follow the (excellent) advice already given.

Hope this helps!

dwayne

PS - we used to make hundreds and hundreds of our own PCB's in the early days of our business.  We would clean the boards mechanically with a fine-grit sander followed by a 3-step chemical cleaning process.  Blow the boards dry with warm air from a vacuum-cleaner motor, then feed the boards through a GBC laminater (modified for lower temperature and higher speed) loaded up with Dupont Riston dry-laminate film.  Exposed the boards with a modified mercury-vapor expose lamp and vacuum frame, then developed the exposed boards with a soda-ash (potassium carbonate?) solution.  Stripped the remaining laminate in a caustic-soda (sodium hydroxide) bath, rinsed, then etched in an Ammonium Persulphate bubble etch tank.

The whole process worked very well but it just took too much time.  We eventually went to CNC milling for PCB prototypes (several years), then quit that and just started using APC for prototype boards.  All of our production boards are now made in China - the quality is extremely high and the cost is astonishingly low.  APC still does our prototype boards.

dwayne


--
Dwayne Reid   <dwayner@...>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
Custom Electronics Design and Manufacturing

Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-07 by James

No I didn't.  I very seldom bother to tin SMD pads.  You must need to be sure the pads are clean, bare copper is fine as long as it's clean, and your flux is good.

For IC's, as I said, pads a bit longer than usual (same goes for all SMD components when hand soldering) bare clean copper, align IC, liberal flux, tack a corner or two, and run along the rest with the iron.

For smaller 2-3 pin devices, put solder on one pad only, hold the iron there on the edge of the pad with molten solder and use it as an end-stop to push the device up against, remove iron, wait for solder to solidify, now just solder the remaining pad(s).


On Sat, Nov 8, 2014 at 5:37 AM, Dwayne Reid dwayner@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
 

The problem with all of the suggestions made so far is that everyone is assuming that the pads already have solder on them


Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-08 by Phil Quinton

Thank you for your replies.. You've certainly given me plenty to try.

I'll have a go and let you know how I get on.

Thanks again for all the help.

Phil.


On 07/11/14 23:27, James bitsyboffin@... [Homebrew_PCBs] wrote:
 
No I didn't.  I very seldom bother to tin SMD pads.  You must need to be sure the pads are clean, bare copper is fine as long as it's clean, and your flux is good.

For IC's, as I said, pads a bit longer than usual (same goes for all SMD components when hand soldering) bare clean copper, align IC, liberal flux, tack a corner or two, and run along the rest with the iron.

For smaller 2-3 pin devices, put solder on one pad only, hold the iron there on the edge of the pad with molten solder and use it as an end-stop to push the device up against, remove iron, wait for solder to solidify, now just solder the remaining pad(s).


On Sat, Nov 8, 2014 at 5:37 AM, Dwayne Reid dwayner@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
 

The problem with all of the suggestions made so far is that everyone is assuming that the pads already have solder on them



Re: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-08 by Mitch Davis

Hi Phil,

On Fri, Nov 7, 2014 at 6:47 PM, James bitsyboffin@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

Put some gel flux (or liquid, but I prefer gel/paste from a syringe) down on the bare pads which you have previously cleaned with whatever solvent you prefer, align the IC, solder down  a pin on one corner to tack it in place, then just drag along the pins with your iron that has been pre-loaded with some solder, or you might prefer to "stroke" away from the pins, or use iron and solder together.  

As James says.

Flux removes existing oxides.  Flux prevents oxidation during soldering.  Flux helps distribute heat.  As well as removing oxides, flux also changes surface tension, helping the solder wet the leads and pads, and making it far less likely that you'll get bridges.

Flux is the answer.  Flux is your friend.

Here's a video of John Gammell in action.  The flux goes on at 1:57.  It's already there at 0:56.  Also note at 1:20, he's heating the pad rather than the pin, and note at 1:35 how long the pads are.

Sigh.  I don't think I could ever get tired of watching this video, but maybe that's just me.

Mitch.

RE: [Homebrew_PCBs] Soldering a LQFP 48 on a home made PCB

2014-11-08 by Boman33

As so many others have suggested bare pads with lots of flux is the way to go.

I would in addition as a first step also brighten up the pads with “Scotch-Brite” scouring pad to remove any stubborn oxidations.

Bertho

Re: RE: [Homebrew_PCBs] Soldering a LQFP 48 o n a home made PCB

2014-11-08 by Rafał Mróz

1000 grit wet sandpaper works too.

--
Wysłane z mojego telefonu za pomocą aplikacji myMail dla Androida.

sobota, 08 listopada 2014, 04:54PM +0100 od "'Boman33' boman33@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>:

 
As so many others have suggested bare pads with lots of flux is the way to go.
I would in addition as a first step also brighten up the pads with “Scotch-Brite” scouring pad to remove any stubborn oxidations.
Bertho