Further Experiments in Solderability/Surface Finish

[mharris]

After my experiment with Silvo last week, I wanted to take things a little bit further

I now have a board with a matrix for testing. I found some Mother's California Gold Metal Polish in a tool cabinet here, so figured I'd add that in too.
MSDS: http://www.homedepot.com/catalog/pdfImages/b7/b7b9b9d7-df26-41c2-bb2d-dc49b32e96b4.pdf

Its more like Brasso than Silvo in that its liquid is Kerosene, however it uses alumina rather than silicates for it's polishing agent. Silvo is Silicates and porcelain clay is isopropyl alcohol. The Mother's polish also has several oily agents within it to help make things look a little shinier and i'm guessing to try to stop it from tarnishing in a hurry.

The test print has 4 columns:
* None - No polishing of any kind will be done on it.
* VPAD - just polished with the Voltera supplied pad - all of the samples other than none get an initial treatment with the Voltera pad.
* Scotch - Going the other direction to fine polish, a scotch pad which we'd normally use for deburring is used to scuff up the surface. I think this will do terribly!
* Silvo - Polished with silvo
* Moth. - Polished with Mothers California Gold Metal Polish

Then rows:
* Cloth - residue removed with just a cloth/paper towel
* ISO - residue removed with isopropyl alcohol
* Ace. - residue removed with acetone.

Each segment in the grid has an 0603 and a 1206 pad, as well as two pads for solder testing - one pad will have paste deposited, the other will be manually soldered.

The silvo is being used by a co-worker so I won't be able to use that until tomorrow.

Gerbers:

Solderability_Paste_Top.gbr (2.4 KB)
Solderability_Copper_Signal_Top.gbr (151.6 KB)

[mharris]

As Printed:

Initial Polish with Voltera Pad - None column is masked.

Scotch Pad, columns on either side are masked to prevent damage.

Mother's California Gold Metal Polish.

[mharris]

Here's the Silvo done:

[mharris]

After giving each sample on the Isopropyl row a wipe down, here is how they look. Each photo is a fixed focus, fixed position, manual settings

Nothing:

Voltera Pad:

Scotch Pad:

Silvo:

Mothers:

Interestingly, the board around the Mother's polished sections appears to be glossier than the board around the rest, with Silvo's realestate being just slightly glossier than the rest of the unpolished sections. There's no appearance of difference where the isopropyl has been applied, so it will be interesting to see if acetone has any effect (its very good at removing fatty/oily substances like the Mothers polish contains.)

[mharris]

OK - this is going to get a bit spammy. There are many images, and to make life easier for me uploading them/keeping them together I'll do a post per surface finish. This section is just paste adherence - Hand soldering will be another day.

As a note, i accidentally desposited paste on both of my bottom pads, so I had to wipe the paste off that one, hence the splattering of tiny solder balls around the place.

The components are an 0603 cap and a 1206 cap.

First: No surface treatment - just the isopropyl and acetone wash.

Nothing done to the ink at all.

Wiped with Isopropyl Alcohol

Wiped with Acetone.

The Acetone wiped 1206 cap is better better adhered to the board than the others. The left side fillet (ie: first photo) is the best of the lot - the right side fillet isn't very good. Further, the solder ball on the pad also appears to be better attached.

[mharris]

Next: Voltera Pad. Same setup.

No solvent:

Isopropyl Alcohol:

Acetone:

The Voltera Pad offers a significant improvement over no burnishing. Again, the Acetone seems to improve wetting out. The 1206 cap has much better wetting out on the acetone wiped pad than it does on the other pads. The solder ball on the lone pad also appears to be much better adhered - but the isopropyl also looks good for the solder ball. Both solvents are better looking in this test than no solvent.

[mharris]

Next: Scotch pad! I was expecting this to do way worse than it did, but it by no means did well.

No solvent:

Isopropyl:

Acetone:

The 0603 on the Acetone wipe is the only one that appears to have much of a chance of staying on the board. On the circuit with no solvent, the parts push off with very little force - I think only flux is holding them on.

[mharris]

Silvo, what originally got me going down this path.

No Solvent:

Isopropyl:

Acetone:

This really didn't work as well as I had expected. The silver in my previous test wet out far easier with hand solder than it did on the Voltera pad burnished board. With the paste this does not seem to be the case.

[mharris]

Mother's California Gold Metal Polish.

No Solvent

Isopropyl

Acetone

Again, quite poor results, but I think they were better than the Silvo results? Very hard to tell with such a small sample.