How to tell quality of components when manufacturing in china - Page 1
Forum section: electronics / projects

author: ctesla75
author_rank: Contributor
timestamp: November 06, 2015, 10:05:02 am
content: Hi All,I am getting some boards assembled in china(elecrow), i have received the blanks and they work using parts from farnell. The next lot i have let them source the parts. My question is how do you know what is a good quality part and what is not, can some parts like resistors and diodes use cheaper substitutesI have asked for part number and manufacturer name this is what they have replieddiodes sm28 - local brand LRCLED - 0805 - local brand ktrlightresistors 0805 - local brand RoyalOhmtransistors sot23 - local brand CJPOT - local brand samsungcap electrolytic - local brand chenxing (through hole)cap electrolytuc - local brand st (smd)opamp - onbridge - TSCthey didnt supply manufacturer part numbers but supplied some datasheets, is it safe to trust therir parts or should i choose more well known brands at a higher cost.thanks ctesla75

author: ciccio
author_rank: Frequent Contributor
timestamp: November 06, 2015, 01:52:42 pm
content: For your information, I've been using RoyalOhm resistors (1/4 and 1/2 W, through hole) for more than a decade, and ZERO problems.I don't know about their SMD types.Best regards

author: dmills
author_rank: Super Contributor
timestamp: November 06, 2015, 02:50:55 pm
content: I would be looking to specify as much as possible from known manufacturers while still meeting your BOM cost target.I always fully specify (with an alternate) everything except the most jellybean of passives, and even then I sometimes get caught.IME the things to be most leery of are parts with limited lives (even if buying good ones), the electrolytic caps in particular are something where I will **ALWAYS** specify the brand and manufacturer part number (Plus an alternate), because a test that an unknown works now says NOTHING about reliability a year down the line.Royal ohm do a fair amount of volume, and are generally ok in a low cost product, no idea about the rest.Regards, Dan.

author: DanielS
author_rank: Frequent Contributor
timestamp: November 06, 2015, 06:26:35 pm
content: There isn't much that can go wrong with resistors.For anything you have specific worries about, you should specify your components. In the case of a switching power supply or any other application with potentially significant ripple current, I would be particularly concerned about the choice of electrolytic capacitors.

author: mariush
author_rank: Super Contributor
timestamp: November 06, 2015, 06:34:18 pm
content: RoyalOhm is distributed in Europe by TME.eu :http://www.tme.eu/en/katalog/?idp=1&search=royalohm&cleanParameters=1I'd pay attention to capacitors, what they offer is probably ChengX ... i'd stay away from them. Go with brand names like nichicon, panasonic, rubycon, united/nippon chemi con .. these are top tier, cheaper stuff but still quite decent would be teapo, taicon, samxon, lelon, maybe even jamicon here then a bit less good but still above chinese crap you'd have su'scon, samwha, ltec ... but what they'll offer to you has a high chance of being fake chinese stuff, or it could be very old stock or could be not so grade series (for switching power supplies it matters, for linear regulators not so much).Not much to go wrong with leds, i'd only be concerned if consistency is important, for example if your board has several leds and you want them all to light up with the same intensity... the lesser known brands may not bin the leds so carefully. I'd also be careful with the selection if your product will face lots of vibrations or humidity which may affect the led lifetime.

author: marshallh
author_rank: Unknown
timestamp: November 06, 2015, 08:23:42 pm
content: You will have to stay on them to keep using your spec'd parts. Don't be surprised to start seeing used/clone parts or the like quietly subbed. Just politely call them out, ask they never do it again or you'll go elsewhere.To prevent this you can say "Any supplier" for non-critical parts. Seems they are doing this for you - just check the prices and make sure you're at least saving money by using these parts over name brand..

author: Vgkid
author_rank: Super Contributor
timestamp: November 07, 2015, 12:23:15 am
content: I will echo Mariush's post, ChengX are really crappy. We had a few in a router, lasted slightly over 2 years. And that was with me keeping it elevated, and clean.

author: ez24
author_rank: Super Contributor
timestamp: November 07, 2015, 07:34:26 am
content: QuoteIn one word - No

author: pickle9000
author_rank: Super Contributor
timestamp: November 07, 2015, 08:36:07 am
content: I agree with trust statement.That said I see a massive number of Chong electrolytics in Chinese made items. It's not a name that would be counterfeited so I wonder what the quality is like?

author: ctesla75
author_rank: Contributor
timestamp: November 08, 2015, 12:26:33 pm
content: Thanks for the replies, I will find some of the mentioned cap brands and supply alternatives, i have asked for actual manufacturer part numbers but they have only supplied part values as i have used in the design and the brand name, luckily it is a fairly simple design and not too much should go wrong hopefully, but it is my first try at manufacturing in china.

author: wraper
author_rank: Unknown
timestamp: November 08, 2015, 12:55:50 pm
content: Quote from: pickle9000 on November 07, 2015, 08:36:07 amAbout those, not sure if not counterfeited, but there are: Chang, Chong, Cheng, Chongx, Chengx, maybe some other variations. I have seen fake Chengx CD110X, stating low esr on them, while on their website these were general purpose series. Esr was very high for a new cap, and rated voltage - 16V was very high for it's size. When applying more than 10V on them, there was few mA leak which was only rising with time, not dropping as when cap is reforming.

author: Howardlong
author_rank: Super Contributor
timestamp: November 08, 2015, 02:04:16 pm
content: Quote from: marshallh on November 06, 2015, 08:23:42 pmThis is my experience too. But whether you spec Farnell/RS etc parts or not, and tell them specifically to use those exact parts, I will guarantee you that they won't. There are fundamental culture differences.As an example, on one project I was using a 1mm PCB with appropriate SMA end launches, I'd specified the exact RS part number. The assembler later complained to me that the connectors didn't fit and they'd had to fudge it. Well, that's because they didn't use the part I'd specified.Second example. They bought cheap "alternative" 1.2V regulators from somewhere, don't know where, despite my specifically giving them the Mouser part number. They had a failure rate of about 50% and the failure mode was to dump the 5V input voltage right onto the 1.2V core of the most expensive chip on the board.Another rather less technical issue with dealing with China is that everything shuts down for two weeks over the Chinese New Year, so plan accordingly.Personally speaking, I will not manufacture in China unless I have someone I know and trust working for me locally there looking after my interests, it's just too risky otherwise, but that is a big expense, and might very well not be worth it, the cost of your agent might well be more than having your boards made on home turf. They will use every way they can to shave a fraction of a penny off. The culture is to give you the nice warm feeling, affirming what you've agreed, and then go and do something different. Getting used to this is hard for a Westerner. You have been warned!

author: mariush
author_rank: Super Contributor
timestamp: November 08, 2015, 02:32:01 pm
content: Quote from: wraper on November 08, 2015, 12:55:50 pmChang is probably the most legitimate out of those and probably of some quality, it's part of Huawei group :http://www.huaweiec.cn/index_en.aspBut like you say, there's lots of chinese companies taking advantage of this so you have ChangX, Cheng, ChengX, Chong and so on, here's some of them :http://capacitor.web.fc2.com/c_other.html#cheng

author: pickle9000
author_rank: Super Contributor
timestamp: November 08, 2015, 07:01:51 pm
content: Quote from: mariush on November 08, 2015, 02:32:01 pmI seem to remember Dave mentioning one in a Rigol teardown, don't know which one though. Could make an interesting experiment. Rigol of course could buy direct of course.

author: mariush
author_rank: Super Contributor
timestamp: November 08, 2015, 07:23:41 pm
content: Quote from: blueskull on November 08, 2015, 07:10:12 pmOh really, that's news to me ... well, at least they have a functional website and actual pdf datasheets.

author: crazy horse
author_rank: Contributor
timestamp: November 10, 2015, 11:10:38 pm
content: I have had to do this before. I went through all the data sheets of their suggested parts and pointed out a few that were not suitable and the reason. The next day I received back modified datasheets with the problem fixed to the value I specified. HmmmWasn't at the company long after so don't know how reliable the product ended being, but one issue that appeared immediately was their relay only had about 70% of the rated isolation so we failed our safety testing.

author: ez24
author_rank: Super Contributor
timestamp: November 10, 2015, 11:30:40 pm
content: QuoteThis is a "service" they will do for you. They will modify a datasheet or spec to what you want - regardless to the truth

author: nctnico
author_rank: Super Contributor
timestamp: November 11, 2015, 12:09:36 am
content: Quote from: DanielS on November 06, 2015, 06:26:35 pmOh yes there is! Think about surge handling, temperature coefficient, tolerance, maximum working voltages, maximum power dissipation, long term stability, etc.

author: Bud
author_rank: Super Contributor
timestamp: November 11, 2015, 01:53:58 am
content: Holy shit, this is depressing and changes the whole concept of offshore manufacturing if you care about your product...

author: dmills
author_rank: Super Contributor
timestamp: November 11, 2015, 02:39:29 am
content: It can be made to work fine, but there are a couple of little details you need to take care of:Firstly, if you specify a target price, they will try to meet it, even if it means fake parts to come in on target, you get (at most) what you pay for.....Secondly you have to do quality control, or have someone with a western outlook over there doing it for you (And making sure the same units that got the QC work get into the containers!), expensive, but we have seen totally wild things come out of the boxes when running our local QC checks.Overall a pain in the arse, and only really worth the aggro if doing a proper volume run where the electronics is a **significant** part of finished goods BOM cost, it is surprising how often this is not the case.

author: coppice
author_rank: Super Contributor
timestamp: November 11, 2015, 03:00:38 am
content: Quote from: mariush on November 08, 2015, 07:23:41 pmWhen you see a familiar looking Chinese name, like Hua Wei, go to the site's Chinese language page, and see what the Chinese name looks like. Even if you can't read it, the lack of a recognisable match for the famous name should raise an alarm. It might be something harmless, like a traditional Chinese vs simplified Chinese rendering of the name, but if the characters don't match be suspicious. Sometimes people are trying to trade on the famous brand's recognition factor. Most times its just that what sounds pretty much the same to western ears is distinctly different if you can read/speak Chinese.

author: analogNewbie
author_rank: Regular Contributor
timestamp: November 12, 2015, 12:21:18 am
content: Quote from: mariush on November 08, 2015, 02:32:01 pmThis is for sure not a member of huawei.com. It is using a different logo. I will report this to our legal department to see what is going on.

author: Howardlong
author_rank: Super Contributor
timestamp: November 12, 2015, 07:23:25 am
content: Quote from: dmills on November 11, 2015, 02:39:29 am100% agreed. I'm no quitter, but when I started having my own designs manufactured five years ago, I had zero experience of contract manufacturing, but how hard can it be? I very nearly gave up after the first run. There is no such thing as a free lunch, and this certainly applies to manufacturing. The biggest risk is being blinded by the headline numbers, you switch to bean counter mode, and forget about the fact that it's cheap for a reason.