Just ordered my first stencil after a hundred years with my electronics hobby and would like to find that best bang for the buck solder paste I can use. No special requirements are needed -- this is just hobby stuff.
I do have a couple that are syringe based and probably want to stick with that as a large quantity would go to waste -- unless small jars are available.
Just a great all around paste for the money. Ordering from China is fine with me as well. -- And they say a credit card works nicely but what else?
mkr5000 wrote in news: email@example.com:
Depends on the sq inch area of the board/stencil. You need a fridge for it regardless. Even you syringe version should be kept cool. Sure they expire, but you only buy one jar. You also need a mechanical stir machine or to stir it yourself before use to re- homogenize any settling that occurs in jars that do not get stirred. That will extend the product life as well as keep the contents most closely matched to the performance spec when sold. Otherwise you can get small pockets of bad paste and get failure modes in production.
As far as charging goes see if they take paypal and use that or get an account with a similar online pay broker they accept. I would not transact card details on online purchases if possible. I use Paypal or other means (buy a walmart visa card and fill it and use that).
+1 on Chip Quik. Their tacky flux is also nice to have around. For LF I've used a lot of amtech lf4300. You can get that from Chip Quik (I think they call it SMD4300 something) or directly from Amtech
Syringe with a stencil will be difficult. I think you will waste a lot of paste unless you can collect it and get it back in the syringe. Small jars are best and you can get 9mo to a year out of them if you keep them cool.
Metal putty knife for small boards or larger drywall knife for larger boards work fine on the stencil. I've tried the plastic bondo spreaders used for body work but they seem to be too thick on the business end. Flexible drywall knifes seem to be the best for me.
I used Chip Quik SMD291SNL10 lead free and it worked well, in a vapour phase reflow machine using Galden LS230 fluid.
I get solder paste all over the place and it is hard to clean up thoroughly, so I think leaded paste would be an ingestion hazard if done at home, rather more so than with wire solder. IIRC roughly each 50 parts per billion blood lead concentration correlates with 5 points lower IQ in children. You can calculate what that would look like but IIRC very very roughly it would fit into a sphere about 0.5mm diameter. Whether that bothers you probably depends on your home circumstances.
Perhaps you have a good technique for avoiding getting paste on things. Without taking special precautions I did get it everywhere and I did not wish to invest time or equipment in that problem as the lead free paste worked great.
For hand soldering, I would prefer to use leaded solder wire if it were not toxic. As a child, I used to hold it in my mouth when I had insufficient hands for all the wires and iron and solder, and some would attribute aspects of my personality to that habit, but I don't do it any more. For surface mount reflow, if the lead-free works well, and in my experience it does, then there is no apparent downside apart from cost, which I can easily afford. The reflow machine did not complain about having to use it, and the results were excellent.
Great. I did and I found the cleanup to be boring hard work.
Performing an order-of-magnitude calculation is helpful in knowing to what lengths one must go, in order to receive the full benefits (if they exist) of not feeding it to one's kids.
As this is usenet, it is not for you to give me homework. The number is approximate and I was careful to use the word correlation rather than claiming causation. Here is an interesting alternative explanation, which also probably gives you references for the correlation:
You need a weighing scale and a child to answer that. The medical literature uses micrograms per decilitre for blood lead level, and I converted to parts-per-billion by mass of blood, as that seems a more intuitive unit. There will be an error due to assuming that lead is homogeneously distributed in humans, but I would rather at least try to make some estimate than none at all.
Yes, probably. Sometimes I try to work out whether something is a credible threat to health by a rough calculation, before deciding whether to ignore it completely. I decided not to completely ignore the potential toxicity of lead contamination due to my use of solder at home, because I couldn't be confident that it would not cause health problems. You might decide that you must use lead because you cannot prove that it definitely will cause health problems. That's your choice.
I still do use leaded solder when it seems worthwhile, like when my Metcal struggles to solder through-hole parts to a huge 6 layer board with too many groundplanes and not enough preheating, but that is seldom and I then clean up carefully.
I had pretty good results with "Shen-Mao solder cream" for 63/37. Lately, I have pretty much gone over to lead-free, and found Loctite GC-10 (made by Henkel) is amazing stuff. It works as well as good 63/37 paste, although you do have to heat to a higher temperature. And, it lasts for an amazing time without refrigeration or other special handling.