Solder Paste for 0201

[olkipukki]

Hi,

I started to explore options and possibilities how to handle 0201 and equivalents SMD components.
The finest paste that I used is Chip Quik T5, and that's fine for the most "bigger" parts (aka 0402).

Quick search and found so called Type 6 - http://www.senju-m.co.jp/en/download/pdf/SMIC_NJ2014_02.pdf

Wondering if someone here has experience with 0201 (or smaller parts) and can share the details.

Many thanks

[glenenglish]

use the reasonable rule of thumb -  minimum of 5 balls width on the stencil aperture. I'd prefer 7 based on the literature.

but with 0201, mixed with larger parts you'll need advanced stencil techniques. stepped etc

[olkipukki]

What about a stencil thickness?
Is there any ratio or correlation to aperture?

[mrpackethead]

There is in deed ratios.  There's a lot of papers on this topic google stencil apature ratios.   You need to take into account both the stencil thickness and the shape of the pad

The problem is that if you have long narrow pads the paste sticks to the sides of the stencil and does not deposit on the pcb properly. 

With parts with large variation on parts size things get harder as you have to balance thickness and size.

I have a board that has an extreme variance on it as I have a very large inductor and .4mm pitch pins. I put some extra paste on the inductor pads by hand. 

You can bend the rules somewhat but it affects yeild and the number of faults you have

[technotronix]

Which technique you are using?

[richardlawson1489]

I don't know much details about solder paste for 0201 but here I found one pdf which tells the detailed information about solder paste for 0201.
http://www3.uic.com/wcms/Images.nsf/(GraphicLib)/0201Webcast14Sept2000.PDF/$File/0201Webcast14Sept2000.PDF

[olkipukki]

Thanks all for the suggestions, much appreciated.

I only tried 0.35mm/0.4mm pitch (WLCSP,xxBGAs) as smallest single components with T5 paste and 100umm stencil, so cannot say that been impressed by the results and far away to be predictable.

As of today, gathering additional info and taking into account previous failed and partially succeeded attempts, will try to work out the "right" apertures and optimize pads, and hopefully repeat 0201/0402 high-density boards with my current abilities. I would not expect the miracle, but a lot of new stuff to learn at least and mighty be good indications (cost $, effort etc.) for future projects.

Meanwhile, not yet give up to get T6 and somewhere find 80umm stencil.

[wraper]

Are you using decent stencil printer?

[olkipukki]

I used http://www.eurocircuits.com/ec-equipment-ec-stencil-mate, that's okay, but definitely is not a precision tool, imho. It seems like the limits already overstretched "We have experience with a pitch of 0.5 mm, and that works fine. A pitch of 0.4 mm should still be possible, but we advise to make the pads in the stencil 5% smaller"

Not yet tried, might have a chance http://www.lpkf.com/products/rapid-pcb-prototyping/smd-assembly/solder-paste-printing/smt-solder-paste-printer.htm

[olkipukki]

Finally, I got both 0.08mm stencil and Type 6 sample paste.
Just tried recently these on WLCSP chips surrounded by 0201s and very pleased with a consistent result, only failure with a stench printer misalignment Well, I am planning to solve this in 2018

[asmi]

I'm using this paste: http://www.chipquik.com/store/product_info.php?products_id=470005 My

board contained about 50 0201 caps, and I only got one tombsone during reflow. The cool thing about that paste is that it's thermally stable, meaning it has to be stored at room temperatures, and it doesn't dry out after printing, giving you all the time you need to place parts, which is very handy for hand-assembly of complicated boards.

[mrpackethead]

That Quick Chip Paste is repackaged Henkel GC10.   great stuff.  500g container is about $80.00..  $17 for 50 is kinda spendy.

http://www.henkel-adhesives.com/loctite-g10-solder-47933.htm

[Kean]

That Quick Chip Paste is repackaged Henkel GC10.   great stuff.  500g container is about $80.00..  $17 for 50 is kinda spendy.

http://www.henkel-adhesives.com/loctite-g10-solder-47933.htm

I was wondering about that - it seemed unlikely they also formulated something so similar.

Now that I have my stencil printer and (second hand) TM240A up and running, I have started using GC10 based on your recommendation.  Don't really need lead-free, but if it isn't too hard then I'd prefer to use it.

Last week I did 10 panels of 6 PCBs per panel containing a QFN28 and TSSOP8.  Everything went quite well apart from the first batch where I had all the TSSOP8's rotated 180° and had to manually rework 24 PCBs!  Still trying to get the profile right on the T-962A, but most boards reflowed fully.  And I still need to streamline the final assembly and testing procedure.  Anyway, the client was really happy with the small batch turn around time, which suits both me and them.  They paid the invoice immediately and have requested another batch for mid January.

Edit: Oh, and no 0201's for me!  There is no way the TM240A could place them, and I don't really feel like doing them by hand.     I have 0402's on some of my more compact designs, but generally stick to 0603 or 0805.

[mrpackethead]

Lead free is a tougher assignment than lead based solder from the reflow perspective.  but i'm yet to find another paste that is as forgiving as GC-10.

[tautech]

I stumbled on this in my archives today, not sure if it'll be of any help or value.

[olkipukki]

I'm using this paste: http://www.chipquik.com/store/product_info.php?products_id=470005 My

board contained about 50 0201 caps, and I only got one tombsone during reflow. The cool thing about that paste is that it's thermally stable, meaning it has to be stored at room temperatures, and it doesn't dry out after printing, giving you all the time you need to place parts, which is very handy for hand-assembly of complicated boards.

What stencil aperture and thickness did you use for 0201?

[asmi]

What stencil aperture and thickness did you use for 0201?

0.35x0.3 mm aperture (same as pad size), thickness 0.1 mm, with electropolishing (without it cleaning stencil after use will be a nightmare).

[HalFET]

Lead free is a tougher assignment than lead based solder from the reflow perspective.  but i'm yet to find another paste that is as forgiving as GC-10.

Can't complain about Interflux's equivalent offering either actually.   

[wraper]

Lead free is a tougher assignment than lead based solder from the reflow perspective.  but i'm yet to find another paste that is as forgiving as GC-10.

Can't complain about Interflux's equivalent offering either actually.

I don't think interflux produces any temperature stable solder pastes.

[HalFET]

Lead free is a tougher assignment than lead based solder from the reflow perspective.  but i'm yet to find another paste that is as forgiving as GC-10.

Can't complain about Interflux's equivalent offering either actually.

I don't think interflux produces any temperature stable solder pastes.

Officially I think not, in practice we have syringes of this stuff sitting on lab benches for months on end with no noticable degradation. It seems to outperform most solder pastes in terms of stability and shelf life. Though I suspect interflux is somewhat modest compared to henkel?

[wraper]

Officially I think not, in practice we have syringes of this stuff sitting on lab benches for months on end with no noticable degradation. It seems to outperform most solder pastes in terms of stability and shelf life. Though I suspect interflux is somewhat modest compared to henkel?

You can say this about many solder pastes. If it seemingly performs ok, does not mean it hasn't significantly degraded. GC-10 officially can be stored for 1 year at room temperature. Modest? Henkel/Multicore has much higher reputation than interflux. And GC-10 is pretty recent product, other solder pastes they produce should be stored in refrigerator.

[SVFeingold]

Adding a vote for GC10. I've used probably 5 other LF pastes from Chip-Quik and Kester, none work as well as GC10 for me.

I think that type 6 paste is overkill for 0201. Type 5 or even Type 4 ought to give acceptable results. Finer solder paste also seeps more readily under the stencil if the gasketing is poor. Keep in mind as you decrease the size of the solder balls you increase the surface area/volume ratio of the metal in the paste. You expose more surface area to the flux and speed up chemical processes that you don't want happening. This is primarily why pastes "go bad."

I'd put more thought into your stencil and your apertures. The $15 add-on stencils that you get from many Chinese fabs won't cut it. I get my stencils from Stencils Unlimited which is more expensive but hassle-free, and they're quite good. They offer more advanced stencils with electropolishing and nanocoatings and etc. that make more sense the smaller you go. I used for manually stenciling a 176-pin BGA with nothing more than a flat stencil and a strip of masking tape, with perfect results. Using the same method I've also done micro BGAs, CSPs, and 0.3mm pitch DFNs with no major issues.

For apertures, I've recently modified all of my Altium libraries to use rounded corners for all pads and apertures. It's helped with paste release. Since you're printing manually your technique is extremely important too. I prefer metal squeegees, the rubbery ones I've tried never work out as well. Get a nice "roll" of paste going and get a nice, even stroke going with firm but even pressure. I find it easier to feel this out with a metal squeegee.

There seems to be no limit on how small apertures get for these parts. Sometimes when I'm watching random PCBA videos in production lines I'll see small passives with only half the pad covered in paste. Wild.

Understencil wipes are also crucial the moment you notice imperfect gasketing. For me this is about every 5 manual prints. Squirt some 99% IPA on the wipe and give it a good rub on the underside of the stencil. For parts (thus apertures) that small I strongly recommend getting some clean-room wipes. Proper cleanroom wipes, not just the green-box Kimtech wipes. Cleanroom wipes are designed not to shed ANY dust or lint. The cleanroom stuff is expensive, but it sure beats digging out tiny fibers left in tiny apertures by "lint-free" wipes. Another reason for rounded apertures IMHO - fewer pointy corners to grab those little fibers. Compressed air (or air duster cans) after the wipe help too, but only blow from the same side you wiped. If you go back and forth you'll more readily trap stuff inside the apertures. Generally speaking though I've found that using cleanroom wipes obviates the need for compressed air. 

[mrpackethead]

I'd put more thought into your stencil and your apertures. The $15 add-on stencils that you get from many Chinese fabs won't cut it.

But the $25 ones do.  Make sure you get an electropolished one.   It makes all the difference.

I get my stencils from Stencils Unlimited which is more expensive but hassle-free, and they're quite good. They offer more advanced stencils with electropolishing and nanocoatings and etc. that make more sense the smaller you go. I used for manually stenciling a 176-pin BGA with nothing more than a flat stencil and a strip of masking tape, with perfect results. Using the same method I've also done micro BGAs, CSPs, and 0.3mm pitch DFNs with no major issues.

For apertures, I've recently modified all of my Altium libraries to use rounded corners for all pads and apertures.

Did you do this automatically?  Or did you use rounded pads?

[SVFeingold]

If there's a way to do it automatically I'll feel real dumb! I just went through and modified every part I used on a new design. Eventually I just stepped through most of them and changed them. Took about an hour.

Pretty much as you said, changed rectangular pads to rounded with usually a 5-15% corner radius. The larger the pad the smaller the radius %. Also started breaking out footprints by manufacturer since different companies give different recommendations. No idea if it truly matters but good practice IMHO.

Examples attached. One issue is that I've started a -.025mm expansion on small passives and ICs as a rule, unless the datasheet calls out different. This means on small pads that even though your pad has a radius, if it's too small the negative expansion of the paste might end up square anyway. And you can't change the paste radius separately AFAIK unless you just make an SMD pad on the paste layer separately. I'll do this sometimes but only for critical parts or tricky footprints.

Also an example of a particularly tricky footprint for me that I haven't converted yet to rounded pads, but this was the recommended footprint. This part is 1x1mm!

[Harjit]

Chipquik seems to have two pastes that are interesting:
TS391SN <- above someone mentioned it is the same as Loctite GC10
TS391AX <- this claims all the great stuff as the TS391SN but it is leaded

I can't find a Loctite GC10 that is leaded. So, I'm wondering if the TS391SN really the same as Loctite GC10?

[asmi]

Chipquik seems to have two pastes that are interesting:
TS391SN <- above someone mentioned it is the same as Loctite GC10
TS391AX <- this claims all the great stuff as the TS391SN but it is leaded

I can't find a Loctite GC10 that is leaded. So, I'm wondering if the TS391SN really the same as Loctite GC10?

Yep, that's the one I'm using. Bought on Digikey, but you can buy it on Chipquik website if you prefer.

I've done several hundreds of 0201 caps with it by now with only one tombstone - and even that one was my fault, not that of a paste.

[mrpackethead]

THere is no GC10 leaded paste.