A most unusual metal

Not really an electrical connector but a Micro HDMI plug on the end of a lead for 'camera to monitor' cable. (Its about the same size as a micro USB on a phone)

The cable is supplied with moulded on plugs and I cut off the outer moulding to investigate shortening the connector because with the camera mounted in its special housing there was insufficient room for this straight plug.

Other connectors of this type usually have a sheet metal folded cover, this one though has two small diecast parts forming a clamshell arrangement. What surprised me though was that the two halves had been soft soldered together, The diecast metal had a whiter than usual appearance so I initially thought it might be tin plated.

The biggest surprise though is that whilst it is plated (layer of copper underneath) the base metal itself solders as easily with 60/40 as any normal electronic component!

In the bottom picture you can see where I have filed away a small area then heated it with soldering iron, the solder wetted the surface instantly.

Any ideas what the metal might be?

Just out of interest, the cable wired to this 20 way connector has 6 twisted wire pairs each individually screened, plus a couple of single wires, and all in a diameter of 2.2mm!

Ian P

If the metal is a silvery colour then it might possibly be nickel-silver, often used in model railway track and associated electrical components. It solders very easily and does not oxidise too rapidly. I think the usual composition is 60% copper, 20% nickel and 20% zinc. It usually does not contain any silver despite it's appearance. Being a copper alloy it is easily formed by pressing or stamping.

Its not like any Nickel Silver I have seen. I am certain its been cast not (pressed, coined or stamped) and if I break a bit off it has the feel of a Zinc based diecasting and the fractured surface is granular.

Ian P

Probably Zamac, or some such zinc/aluminium alloy used for die casting, commonly known as "monkey metal", because of its fondness for falling to pieces after a couple of years, or when stressed beyond its very limited limits! Its great advantage is that it is ridiculously CHEAP!

Phil,

Ian said that he's soldered to it - I don't think you can soft solder Zamac.

A possibility that occurs to me is that the two halves of the housing have been electro-formed rather than cast.

Best regards,

Swarf, Mostly!

.

I was going to posit that, too ... but then I couldn't get my head around the process

The marks could be on an injection moulded form, which is then melted/burned/dissolved away after the electro-forming ... but that result in a hollow shell ... and if left in situ then presumably there would be burning when Ian soldered to it.

Mmm

MichaelG.

Electro-formed I'm not sure about but I assume its different to electro depositing. I do not think either are applicable to this part though.

I am sure its some sort of casting process in a die, its the easy solderability of the base metal that intrigues me. Its definitely not like any Mazak or Zamak that I have ever come across. The cable is a supposedly better quality than cheap imported ones (but its still imported from China!) and it is a mass produced item.

Ian P

Are we talking about something like this, Ian ?

**LINK**

http://cvp.com/index.php?t=product/atomos_atom4k60c1

... the description of which does indeed state (Die Cast Metal)

[ at that price, it's probably Unobtanium ]

MichaelG.

Michael

No its not that actual one. It was free issued to me but its from Lindy cables. (cromobylindy.com £13 plus Vat, but its not coiled and its not got the Atomos name!)

The CVP description mentions Diecast, the larger 'standard' size HDMI end connector is the usual sheet metal type (you can see the 'jigsaw' shaped joint) but the micro connector looks to be identical to the Lindy one (albeit with a different overmoulding. The gold coloured plated bit looks the same as the one I have and also tins easily (presumably to the plating).

Lindy don't mention the diecast bit either.

Ian P

I would guess that part has been metal injection moulded

You can get Copper and Brass Alloys for die casting. Not cheap. They're sometimes used to make RF connectors that are silver or gold plated to resist corrosion. My guess is that Ian's mystery metal is nickel plated die cast brass.

Definitely not copper or brass based (unless those metals are available in white!)

The extreme RH end in the second picture, where I filed a step to expose the underlying metal has the blob of solder stuck to it. Its as white as aluminium.

Ian P

You're probably right Ian, but a high zinc brass could be very pale yellow. Try soaking a sample in white vinegar or patio cleaning acid overnight. Green corrosion is characteristic of Copper (light green could be Nickel), and if the metal underneath goes pinkish you've got copper.

Also, Zinc, magnesium and Aluminium are attacked by alkalis. Try the same test with Washing Soda or Caustic Soda solution. Bubbles indicate one or more of those metals.

Might be revealing to blast it with a blowlamp. Does it melt, burn, or resist? What colour is the flame?

Dave

Well, I'm intrigued but not so much that I will be getting into chemistry or pyrotechnics!

All I know is that its pure white and solders easily and its finely detailed so was probably made by metal injection.

IanP

Ejector pin marks to get it out of the mould suggest it is just a zinc casting.

Are ejector pins unique to zinc castings?

Ian P

Silly idea of the day [probably] ... The underlying metal is Silver, for its electrical loveliness; and the plating provides a hard shell for mechanical robustness.

MichaelG.

Ejector pins are used on pressure die casting tools as well as zinc casting tools and plastic mould tools.

I'd be surprised if it wasn't AZ91D alloy, die cast. It is a very common alloy used in many electronics enclosures including connector housings all the way to laptop chassis.

No, ejector pins are not unique to zinc die casting, various versions of them are used in virtually all die casting moulds/dies and also injection moulds for all sorts of materials (thermoset plastics, thermoplastics, thermoplastic elastomers/rubber, and waxes.

.

Thar's an interesting suggestion, Jeff

**LINK** https://www.dynacast.com/az91d

But, being mostly Magnesioum, would you also be surprised if it did 'take' ordinary soft solder so nicely ?

MichaelG

.

[quote from Ian's opening post]

"The biggest surprise though is that whilst it is plated (layer of copper underneath) the base metal itself solders as easily with 60/40 as any normal electronic component!"

Edited By Michael Gilligan on 18/09/2017 07:24:58