Surface finish for pins and headers that are not gold.  What is that? - Page 1
Forum section: electronics / beginners

author: JoeN
author_rank: Frequent Contributor
timestamp: April 01, 2016, 06:51:28 am
content: And is it always inferior to gold finish? Superior in any applications? Also, is the gold finish always gold or are their other inferior finishes that resemble gold? Thanks for any help.

author: danadak
author_rank: Super Contributor
timestamp: April 01, 2016, 11:21:14 am
content: Representative todays plating -http://www.ti.com/lit/an/szza046/szza046.pdfhttp://www.ti.com/lsds/ti/high-reliability/packaging.pageRegards, Dana.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 01, 2016, 01:49:25 pm
content: Nickel, tin and bismuth are the next most common platings, I think. (Given that "gold" includes any underplating, i.e. ENIG, NiPdAu, etc.).Nickel is usually a lot worse than bare copper, because of its poor solderability. Bare copper can be rather good if treated (OSP), but this is only used for PCBs, AFAIK.Tim

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 01, 2016, 03:14:56 pm
content: Here is a paper that shows the tradeoffs in connector and header applications. It generally says noble metal finishes are better.http://www.newark.com/wcsstore/ExtendedSitesCatalogAssetStore/cms/asset/images/americas/common/storefront/te_amp/Materials-And-Reliability.pdf

author: JoeN
author_rank: Frequent Contributor
timestamp: April 02, 2016, 08:09:39 am
content: Quote from: danadak on April 01, 2016, 11:21:14 amHoly cow, there is so much to know. And as usual, it seems TI knows everything. Thanks.Thanks for the other commenters as well.Quote from: T3sl4co1l on April 01, 2016, 01:49:25 pmBut as a header material (insert and remove maybe a few times), is nickel a good choice? That's what I am thinking of here. The quality of headers. I guess solderability matters for the soldered end, but I am more worried about the part exposed to air and making contact with a receptacle. Obviously gold never tarnishes. I am trying to figure out how good the other finishes are compared to gold.Quote from: CatalinaWOW on April 01, 2016, 03:14:56 pmWill read this as well.I am mostly interested in if cheapo Chinese headers are decent quality or not. They are so very inexpensive compared to the ones offered at Digikey. Of course, the ones offered at Digikey are so expensive as to be unbelievable sometimes. (e.g.http://www.digikey.com/product-detail/en/harwin-inc/M50-3501042/952-1386-ND/2264367)

author: apelly
author_rank: Unknown
timestamp: April 02, 2016, 09:17:51 am
content: Quote from: JoeN on April 02, 2016, 08:09:39 amI see. Thank you.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 02, 2016, 10:17:54 am
content: Quote from: apelly on April 02, 2016, 09:17:51 amI use so many headers in my projects I wouldn't be able to complete them if I was buying them from Digikey (which I do use for semiconductors). And yet it is an important enough subject that I want to know all the finishes for these headers. I am reading the documents provided by helpful respondents.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 02, 2016, 03:55:15 pm
content: Quote from: JoeN on April 02, 2016, 08:09:39 amAFAIK, tin and gold are the most common for headers; both are good, with tin being better for connectors that provide good wiping force and don't need a good ohmic contact (e.g., power pins), and gold better for small signal applications that need a reliable ohmic contact.Mixing them is bad, because intermetallics form on contact (slowly via diffusion).Nickel and other hard platings (chrome, rhodium) aren't very common, used mainly for mechanical reasons (abrasion and corrosion resistance). Nickel and chrome have an oxide surface layer, that can be inconvenient for electrical connections (obviously), or in the case of nickel, can also cause rectification or distortion effects (relevant to nickel plated BNCs and other RF connectors).Tim

author: onlooker
author_rank: Frequent Contributor
timestamp: April 02, 2016, 04:24:23 pm
content: For pin headers, plating is one thing the core/substrate material is another. It may be copper alloy or steel. Is this important?Obviously copper alloy is more expansive and on Ebay and Ali, some sellers actually list steel pin headers as made of copper. I encountered one and asked for a full refund. For the cheap kits or ready made small boards with pins headers I bought on those sites, it can be a little random, but most times, they use steel pin headers.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 02, 2016, 05:15:46 pm
content: The article I referenced covers most of this, but remember that connectors are systems. They trade off cost, insertion force, vibration resistance, size, ease of assembly and other parameters. They work best when used in the environment they are designed for. Doing it right requires good quality control on contact pressure and the geometry of the mating surfaces as well as the surface finishes. While I don't know if the Digikey connectors are priced appropriately (fairly), but there is a fair amount of work in getting it all right. We engineers are part of the problem. By demanding the "perfect" connector for every application we have created a situation where there are many thousands of connector configurations, minimizing the opportunity for economy of scale and for competition between different vendors of the same item.I have always had excellent success with connectors from major brand names, even when purchased from surplus sources or when using salvaged materials.When using low priced off brand connectors I have frequently had success, but also had a significant number of failures, some not immediately evident. The problems are all over the place. Low quality pin material that didn't maintain contact force. Improper dimensions that force good connector contacts beyond their yield point. Thin plating that wore off after a small number of insertions. And so on.You will have to decide whether you are willing to discover these problems yourself. A lot depends on what your reliability needs are. I will point out that in a newly designed system you often have plenty of problems to figure out without worrying whether your signals are getting to their destination each and every time you hook up your instruments.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 02, 2016, 07:21:42 pm
content: Quote from: onlooker on April 02, 2016, 04:24:23 pmI guess I will grab a magnet and check. I assume all the steel ones respond to magnets.EDIT: Thanks. There was only one set of headers that responded to the magnet. In fact, it was the latest set of headers I received that had the "nickle" finish that had made me ask this question in the first place. I thought those headers looked cheap and I haven't started using them yet. I am going to set them aside and order more from Tayda. I still have headers I got from them and they do not respond to the magnet. Lesson learned there.What I bought vs Tayda ($6 vs $15 for 100):http://www.ebay.com/itm/262136738077http://www.taydaelectronics.com/40-pin-2-54-mm-single-row-pin-header-strip.html

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 02, 2016, 07:37:34 pm
content: Maybe. Beryllium-copper is an excellent base material for connectors, and is non-magnetic. AFAIK stainless steel is not used for connectors, but it might be. Several kinds of stainless steel are non magnetic.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 02, 2016, 07:42:29 pm
content: Quote from: CatalinaWOW on April 02, 2016, 07:37:34 pmThe cheap headers above respond strongly to the magnet. Must be steel of some sort.The Tayda headers are PBT/brass/gold, according to their datasheet. I will stick with that going forward. Then I know what I am getting.http://www.taydaelectronics.com/datasheets/A-197.pdf

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 03, 2016, 03:32:32 am
content: Quote from: CatalinaWOW on April 02, 2016, 07:37:34 pmI think stainless is common for non-electrical structural parts: clips, clamps, frames, hold-downs...Aluminum too (in various finishes: bare, anodize, alodyne or chromate, etc.).Obviously(?), neither is any good for small electrical contacts. Might be okay for connector shells and such, but those have wide potential-contact areas, so still do good for shielding.Tim