Specifications for solder alloy Bi50Sn42Cu8? - Page 1
Forum section: electronics / general

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 02, 2021, 10:58:19 pm
content: Bi50Sn42Cu8 is the alloy claimed to be in a chinese wire solder product (M026 or XW6), and claims 138C melting point, but no other info (eutectic?). I cannot find any references for this alloy, and as it's a chinese brand ("mechanic") I cannot find a technical data sheet or any other resource.Anywhere I should look?Thanks!

author: helius
author_rank: Super Contributor
timestamp: February 03, 2021, 12:20:49 am
content: I know that Bi57Sn43 is eutectic at 138°C. No, I didn't find any information about your alloy, maybe you need to translate it into Chinese somehow. Copper content could affect the joint strength and intermetallic formation.One fairly easy test you can do is to attempt to wet the solder onto a pre-cleaned small square of copper-clad PCB material. If it achieves liquidus at near 138°C, a soldering iron held at 175°C should be able to wet it completely smooth and flat. If this doesn't work it may not be eutectic (hotter liquidus than solidus).As an example of a non-eutectic solder, I have a pound of Pb62Sn25Bi10Ag3: solidus 124°C, liquidus380°C!! How's that for a plastic range. I wonder what it was used for?

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 03, 2021, 02:35:50 am
content: Thanks so much for the practical guidance! Some "I've done it" experience is really helpful.I'm afraid for the "mechanic" branded products, there's no detailed information beyond labeling on the package and some very rudimentary (and incomplete) information attached to the ebay listing where I found the product in the first place. Sounds like next step (before trying it experimentally) is to see if it's possible to machine translate chinese from the package labeling.Thanks again,Dave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 03, 2021, 03:25:28 am
content: Thanks!That (pictured) is the material I found.From the package labeling, does it tell you who the manufacturer is ("mechanic" - is it a brand, or a company name? if it is a brand, is there another company name?)Bi/Sn is normally used for this type of application, however, the addition of Copper is not something I have seen before (there are some other "dopants", but the only one I've seen normally is 0.4% or 1.0% Ag.)Thanks again,Dave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 03, 2021, 03:47:16 am
content: OK, I thought probably not eutectic is trade-off, so this is good to confirm.Does mechanic have web site (URL?)Thank you again for your help!

author: srb1954
author_rank: Super Contributor
timestamp: February 03, 2021, 04:06:26 am
content: Quote from: helius on February 03, 2021, 12:20:49 amIn olden days power and telephone cables were made with a lead sheath and when jointing these cables the lead sheath was made good by a process called "wiping" which might have used an alloy such as this.The cable jointer would heat up the alloy until it was almost molten and then grab a rag in his hand and use that rag to wipe the plastic metal alloy over the joint filling in the gaps. Having a very wide gap between solidus and liquidus greatly facilitates this wiping process as it gives the cable jointer more time to work the joint before the alloy solidifies.Nowadays I guess this process is just another long forgotten trade.

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 03, 2021, 04:08:58 am
content: Can you direct me to their online store?Thank you again,Dave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 03, 2021, 02:57:02 pm
content: Thank you again - I understand.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: February 15, 2021, 03:34:26 am
content: i did ordered one, that on the picture , it does melting at 150 -my lowest temp on tip. if i use heatgun at 160 , it became mmm.. brittle or friable structure , sooo yes it a low temp alloy

author: wb0gaz
author_rank: Frequent Contributor
timestamp: February 15, 2021, 02:35:19 pm
content: Thank you - you probably saved some others (including myself) from re-inventing the wheel.I imagine the solder alloy is not eutectic, but it does sound like it would fit some needs for low-temperature alloy.