Why are most semiconductor cases black ?  - Page 1
Forum section: electronics / general

author: Miyuki
author_rank: Frequent Contributor
timestamp: June 27, 2018, 04:52:26 am
content: Hi folks,I just saw some vintage NEC transistors and they are in green epoxy mold (TO220)I newer saw it before, just common black/gray onesHave it some reason or why we have no colorful semiconductors ?

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: June 27, 2018, 05:01:26 am
content: Semiconductors are generally light sensitive, so black epoxy will prevent them from reacting to ambient light.https://www.raspberrypi.org/blog/xenon-death-flash-a-free-physics-lesson/

author: Zero999
author_rank: Super Contributor
timestamp: June 27, 2018, 07:55:18 am
content: Quote from: radar_macgyver on June 27, 2018, 05:01:26 amPresumably they rules out the EMP generated by the capacitor in the xenon flash gun discharging, which I would have thought would be much more likely to cause this.

author: RoGeorge
author_rank: Super Contributor
timestamp: June 27, 2018, 08:40:04 am
content: Quote from: Hero999 on June 27, 2018, 07:55:18 amThe EMP itself might be enough, but I tested myself by pointing a pen size green laser on the RPi's LDO. It resets the RPi instantly, every time.

author: Synthtech
author_rank: Regular Contributor
timestamp: June 27, 2018, 08:59:17 am
content: I’m sure that some university “professor” will soon publish a paper on the “Patriarchy of semiconductor case colouring and it’s implications for climate change”.

author: coppice
author_rank: Super Contributor
timestamp: June 27, 2018, 09:02:21 am
content: I think a more interesting question is why are cases sometimes not black. Black is cheap, and cheap is good. However, some parts, like opto-couplers, are made in large quantities in other colours. Why is that?

author: mariush
author_rank: Super Contributor
timestamp: June 27, 2018, 10:47:36 am
content: Optocouplers use infrared or other wavelengths, and other colors than black may be better for that purpose.Also have some vague memories about something to do with heat (retaining, absorption, fluctuations etc)... black is worse than white or other colors when it comes to heat.

author: BrianHG
author_rank: Super Contributor
timestamp: June 27, 2018, 07:17:12 pm
content: Now for Orange:

author: CopperCone
author_rank: Super Contributor
timestamp: June 27, 2018, 07:46:20 pm
content: replaceable black parts chained down by copper doing all the work on green boards someones gotta change that

author: wraper
author_rank: Unknown
timestamp: June 27, 2018, 07:53:29 pm
content: Quote from: mariush on June 27, 2018, 10:47:36 amBlack is good for heat radiation and absorption, yes it works both ways. Although what is black in visible spectrum is not necessarily in IR and vice versa.QuoteDefine "worse".

author: jaromir
author_rank: Unknown
timestamp: June 27, 2018, 09:25:42 pm
content: Russian semiconductors often did have different than usual black epoxy bodies, likehttps://commons.wikimedia.org/wiki/File:USSR_K155LN1_(%3D7404).jpg(though they had different specialties, like this 8086 clone -http://www.cpu-zone.com/8086/DSCF1285.JPG)or jelly-bean transistor KT315https://en.wikipedia.org/wiki/KT315#/media/File:Kt315b.jpgthough typical KT315 package has orange-red colorhttp://dragmet.netdo.ru/uploads/images/73/3f/733fae540f99fff0d6d6542c0101e64a.jpgThe brown color of IC packages earned them a lot of unflattering nicknames.

author: BrianHG
author_rank: Super Contributor
timestamp: June 27, 2018, 11:24:56 pm
content: Darn, cannot find a photo of those really old blue TRIACS you used to be able to get in TO-220 package.

author: wraper
author_rank: Unknown
timestamp: June 27, 2018, 11:36:53 pm
content: Quote from: BrianHG on June 27, 2018, 11:24:56 pmThis?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2018, 11:41:46 pm
content: Both pictures showcase something else unusual: the full breadth of the TO-220 package standard. The leads are allowed to be round or rectangular, the body dimensions can be all over, and the tab thickness can be as thin as the leads, or as thick as the more familiar TO-220AB (which is what most people know today, and what most think of, when thinking of TO-220!).Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2018, 11:44:28 pm
content: Regarding color, I've seen green PNP power transistors more often than NPN.There are also white packages typically for optos, which usually improves CTR slightly.Package color is irrelevant at radiation wavelengths, in the long IR. The resin completely dominates.Tim

author: BrianHG
author_rank: Super Contributor
timestamp: June 27, 2018, 11:49:51 pm
content: Quote from: wraper on June 27, 2018, 11:36:53 pmYes. Here are blue-ish pnp transistors.I don't remember seeing white TO-220, but I have seen a true light grey case.We are missing brown, yellow and purple needed to finish the rainbow.

author: Nauris
author_rank: Regular Contributor
timestamp: June 28, 2018, 04:00:29 pm
content: Quote from: T3sl4co1l on June 27, 2018, 11:41:46 pmBut ain't that a TO-202 that that SC136BI is in?

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: June 28, 2018, 04:37:30 pm
content: What I can't understand is why they print the numbers on a black case with black ink.

author: wraper
author_rank: Unknown
timestamp: June 28, 2018, 05:17:22 pm
content: Quote from: IanMacdonald on June 28, 2018, 04:37:30 pmI don't know any of such components.

author: BrianHG
author_rank: Super Contributor
timestamp: June 28, 2018, 06:59:23 pm
content: Quote from: IanMacdonald on June 28, 2018, 04:37:30 pmAre you talking about laser etched/burned printing on components. Laser printing uses no ink, cant be easily rubbed off, 10x finer print, 10x faster printing, and the printer lasts almost indefinitely compared to paintjet or silkscreen print, but,,, there is that annoyance that if you want to read the numbers, your source light need to be at an off angle to easily see the burned depressions.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 28, 2018, 07:47:18 pm
content: Quote from: Nauris on June 28, 2018, 04:00:29 pm"Both pictures" as in, the ones picturing TO-220s.Tim

author: BrianHG
author_rank: Super Contributor
timestamp: June 29, 2018, 01:40:46 am
content: Surprise, look at what I found!Though I believe that's ceramic, not plastic.

author: SeanB
author_rank: Super Contributor
timestamp: June 29, 2018, 04:43:30 am
content: Purple ceramic on a RF power device is almost always a very strong indicator the ceramic is based on Beryllium oxide, a very good thermal conductor, a very good electrical insulator with very low RF losses, but also incredibly toxic in the form of dust if the package is broken or handled roughly.Purple or pink is dangerous, a white ceramic is almost always alumina, which is safe to handle.

author: CJay
author_rank: Super Contributor
timestamp: June 29, 2018, 05:02:54 am
content: Quote from: T3sl4co1l on June 27, 2018, 11:44:28 pmSimilar with MOSFETs, I've a pile of complimentary Hitachi parts, the 2SJ P type parts are green, the 2SK N types are black.

author: BrianHG
author_rank: Super Contributor
timestamp: June 29, 2018, 05:47:49 am
content: Quote from: SeanB on June 29, 2018, 04:43:30 amThe 3 main custom chipset ICs in my Amiga 1000 are all purple 48 pin ceramic ICs, with gold pins. Are you saying I should be extra careful with them?

author: CJay
author_rank: Super Contributor
timestamp: June 29, 2018, 09:24:00 am
content: Quote from: SeanB on June 29, 2018, 04:43:30 amNope, there are many many BeO RF devices in pure white and they're in current production too.They're all safe to handle up to the point where it is reduced to dust and ingested.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 29, 2018, 07:25:23 pm
content: Quote from: SeanB on June 29, 2018, 04:43:30 amNo, BeO is white, those are actually polycrystalline ruby -- chrome doped alumina ceramic.Only place I see reference to pink BeO is idiots screaming about it on YT...Tim

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: June 30, 2018, 04:48:28 am
content: Confirmed, one of our radar transmitters has a bunch of BeO insulated transistors, and they're all white.

author: station240
author_rank: Unknown
timestamp: July 02, 2018, 09:02:54 am
content: I've got some BD139 or BD140s in grey packages.Too cold and dark to go find them, so here is a random photo off the net.

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 02, 2018, 01:25:54 pm
content: The VERY old 'OC' Series Transistors used to have black painted glass envelopes.https://www.google.com.au/search?q=oc+series+transistors&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiMy_aYwYDcAhUKWbwKHTSFDtkQ_AUICigB&biw=1335&bih=645#imgrc=TA6dsxA1UySTrM:We used to scratch off the black paint, to make photo-sensitive devices !!!

author: Gyro
author_rank: Super Contributor
timestamp: July 02, 2018, 02:44:25 pm
content: QuoteOh yes, I remember that. The early OC71 was the favorite.When Mullard found out, they spoiled the fun by changing the internal paste from clear to opaque white. They then released an opto version as the OCP71, with clear paste and no paint... for more money of course!I remember filing round the bottom of the later ones to remove the glass, washing the paste off the junction and out of the glass with Paraffin and then sellotaping the glass back on (I was cheap!).

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 02, 2018, 05:39:03 pm
content: Quote from: GlennSprigg on July 02, 2018, 01:25:54 pmLike this glass phototransistors

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: July 02, 2018, 06:47:28 pm
content: Old "Kulon" cases. Mostly they were white, but not only:http://www.155la3.ru/k237.htm

author: CopperCone
author_rank: Super Contributor
timestamp: July 02, 2018, 07:36:37 pm
content: so what do microwave magnetrons use? Are they using berylium oxide? I also thought it was suspicious that BeO would be pink. It's not pink when pure and Be does not tend to make colors. Transition elements make colors.Do they dope it on purpose or is just manufacturing cheapness?

author: AllTheGearNoIdea
author_rank: Unknown
timestamp: July 02, 2018, 08:50:55 pm
content: It’s slimming and black goes with everything!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 02, 2018, 09:00:15 pm
content: Because they use alumina (doped with chromium, making artificial ruby as it were).Tim

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 03, 2018, 03:59:43 am
content: Quote from: CopperCone on July 02, 2018, 07:36:37 pmAny magnetron with BeO would be clearly labeled, unless they were made in the '50s or '60s. Most don't use it unless there's a good need for it (very high power), often it's on the output window. The only tubes I've come across with BeO are 1.2 MW Klystrons (on their output windows).

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 03, 2018, 01:36:20 pm
content: I got a weird shaped red one.It's the regulated secret squirrel chip that runs the special algorithms and RNG (I think) for a Japanese slot machine.

author: coppice
author_rank: Super Contributor
timestamp: July 03, 2018, 09:30:44 pm
content: Quote from: TERRA Operative on July 03, 2018, 01:36:20 pmThat looks like the kind of package that will have added substantial cost to the part. Any time you want to use a package that's not off the shelf it adds horribly to the part's cost.

author: RoGeorge
author_rank: Super Contributor
timestamp: July 03, 2018, 09:58:49 pm
content: Judging by the seal stick over the chip, I bet RNG would stands here for (true) Random Number Generator.If so, then the testing of such a part will cost way more than the part itself. Testing for true randomness is not trivial, and very time consuming. Each part must be tested individually.Testing time in general is very expensive, and for such a part could easily become the main cost. I guess the cost for such an exotic case would not contribute much in the total price.Never seen something like that before, thanks for the pic!

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 04, 2018, 07:08:06 am
content: Yeah, I plan to salvage this board (Got a nice Z80 CPU and some other useful bits too) and I would like to decap the chip and see what's inside.I might have to send it to the likes of electronupdate to have a look inside...

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 04, 2018, 12:26:51 pm
content: Quote from: Gyro on July 02, 2018, 02:44:25 pmYea, you are right mate !!!! Heaven forbid people might resort to their own ingenuity !!! xox

author: bsfeechannel
author_rank: Super Contributor
timestamp: July 04, 2018, 10:52:38 pm
content: And I thought I was special because I had a green diode.

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 12, 2018, 11:53:02 am
content: Quote from: bsfeechannel on July 04, 2018, 10:52:38 pmWHAT !!!!! They are HIGHLY RadioActive !!!!!Bury it in a Lead container in your neighbors back-yard.....and spray your workshop with "Rads-Be-Gone"...

author: NEYi
author_rank: Contributor
timestamp: August 31, 2019, 12:12:32 am
content: Remembered of an old video I made.https://youtu.be/pwo9-BxnC_Y

author: vk6zgo
author_rank: Super Contributor
timestamp: August 31, 2019, 05:18:45 am
content: Quote from: GlennSprigg on July 04, 2018, 12:26:51 pmAn old mate of mine built an "optically triggered" ignition system from an Electronics Australia article.The main bits which made this different to the other "transistor ignitions" & "CDIs" they had featured, were a slotted metal disc to replace the points, an infrared source & a photo transistor.You could make the disc yourself, or buy one----Bob made his own one (beautiful job, too!)."EA" used a very small incandescent lamp, run from a lower voltage than its rated one for the infrared source-------Bob found a similar device in the "junkbox".Finally, the optotransistor, this was a silicon NPN device, so Bob cut the top off an unmarked "candy jar" transistor*, fitted a perspex window, & was good to go!*I have posted before about General Accessories in Perth, & their practice back in the day of selling"cleanskin" NPN & PNP silicon transistors out of "candy jars".I have no idea where they got them from, but they were "dirt cheap" & were pretty much useablein circuits specifying the smaller "BC" series ( BC107, BC177).Bob used a lot of them!Back on topic, I have seen quite a number of semiconductors in other than black packages.STC sometimes used white PNP Ge devices, & one Japanese company ( I can't remember who) usedvery light green.I have seen some devices in the "TIP" family of transistors in red packages as well as the green NEC devices referred to by the OP.Strangely, black has seemed to go out of fashion for diodes---all the old Philips/Mullard diodes were black, but most small signal diodes are clear these days.

author: windsmurf
author_rank: Frequent Contributor
timestamp: August 31, 2019, 08:29:40 am
content: White seems to be common too...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 31, 2019, 02:19:44 pm
content: Not plastic though -- those were pure alumina ceramic!Dunno offhand what the more common purple ceramic is, guessing alumina with impurities (chromium?) added for whatever reasons (stability, expansion, leakage, opacity?).Tim