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I have noticed that occasionally some USB mini-B connectors have what looks like a transparent yellow tape on their top.

It might be Kapton tape, but I am not sure.

As an example, please see the below image:

Adafruit 284

(source)

Usually, I leave this tape on. I am wondering, does anyone know what this yellow tape is for?

All I can think of is for protection during soldering, but I am not sure if that's applicable for machine-soldered circuits.

Intrastellar Explorer
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    kapton is standard tape for wave soldering and IR. here the flat surface allows suction pick and place – Tony Stewart EE75 Aug 18 '20 at 21:47
  • It is a little bit confusing. So Kapton tape can change a rough surface to become a flat surface? Never heard of Kapton in my life. All my life I hear CelloTape and Cellophane that can keep my hands and food from Corona virus. Refs: (1) Kapton - Wikipedia https://en.wikipedia.org/wiki/Kapton (2) Cellophane - Wikipedia https://en.wikipedia.org/wiki/Cellophane. – tlfong01 Aug 19 '20 at 01:17
  • Now I wikied and realized that the EU DuPont guys are perhaps smarter, because it is them inventing Kapton and Cellophane. Not sure if the 3M guys copycated DuPont and made world famous cellotape. – tlfong01 Aug 19 '20 at 01:28
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    @tlfong01, Du Pont invented Kapton and commercialized Cellophane, but 3M probably invented the adhesive that makes the tape sticky. (confirmed [here](https://en.wikipedia.org/wiki/Scotch_Tape#History)) – The Photon Aug 19 '20 at 06:20
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    @tlfong01 Kapton tape itself is smooth and mostly none vacuum penetrable. So by gluing it to a rough/open object, it provides a way for a vacuum to suck it up. Kapton Is a name brand for a synthetic polyamide more like Nylon than Cellophane which is organic or semi organic and older. Cellophane does not have the heat resistance of polyamids. Kapton is mostly used in industrial applications and not consumer ones. – Passerby Aug 19 '20 at 06:36
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    Related: [What is the purpose of this disk over a Samtec connector?](https://electronics.stackexchange.com/q/501877/53015) – Mast Aug 19 '20 at 08:17
  • Ah, I have a similar question which I have long been too afraid (of losing face) to ask. I from time to time buy piezo buzzers, and every time each of them has a little disc on top, saying something like "***remove seal after washing***". What I don't understand is what why washing? I never wash anything, so can I just remove it. Perhaps the disc is also for PnP machine which will automatically wash and remove the disc? AliExpress 3v 12mm Piezoelectric Buzzer US$1.29/10 units / to continue with link, ... – tlfong01 Aug 19 '20 at 13:28
  • / ... AliExpress 3v 12mm Piezoelectric Buzzer US$1.29/10 units https://fr.aliexpress.com/item/33004601553.html?spm=a2g0w.search0302.3.22.537435f2APWeyT&ws_ab_test=searchweb0_0,searchweb201602_0,searchweb201603_0,ppcSwitch_0&algo_pvid=ab0943f4-3233-4bd4-b6a1-156c1fbf82bf&algo_expid=ab0943f4-3233-4bd4-b6a1-156c1fbf82bf-3. PS, I never see this washing instruction in other components. – tlfong01 Aug 19 '20 at 13:29
  • @Passerby, many thanks for the industrial English lesson. You remind me long time ago when I first worked as a technician, I already have studied English language for 5 years in school. But then I did not know much everyday English. I still remember a Scot guy with some scot accent, asked me things like "Do you have a "biro", "cello tape", "Araldite"?. At that time I only knew "ball pen", "transparent plastic tape", "mix glue". I never heard colloquio so I felt nervous talking to foreigners. My written English was broken, but spoken English was worse. I have no problem in BBC radio, though. – tlfong01 Aug 19 '20 at 13:54
  • @Photon, ah yes, as a child I learnt that Du Point 24k gold cigarette lighter was only for high class society, kings and queens. I never thought that Du Point invented so many industrial and home products. I always wrongly thought that DuPont, like Leica camera, were best in the world, the Japanese guys Nikon, Cannon etc try to copy for decades but could never surpass. – tlfong01 Aug 19 '20 at 14:02
  • @tlfong01 the wash sticker can help for pick and place but it is there to prevent liquid from getting inside when a board is given a bath to remove flux, or to protect against board sealant/conformal coating. If liquid gets inside the piezo it can get stuck there or damage it. – Passerby Aug 19 '20 at 14:12
  • @Passerby, Ha, so it has a special name "wash sticker". I googled "wash sticker" and found this educational Q&A telling the long story and a joke: "Remove After Washing" on Piezo Buzzer - EESE Asked 6 years ago Viewed 28k times: https://electronics.stackexchange.com/questions/98556/remove-after-washing-on-piezo-buzzer. So it is a common "stupid" question that 28k newbies were too afraid to ask! PS - I think yellow wash stickers are for human hands to pick and place. The above Q&A mentions that there is the yellow wash sticker for vacuum pick and place. – tlfong01 Aug 19 '20 at 14:26
  • I often see big robot arms that vacuum sucks chips to place on PCB. I never have a chance to see small vacuum sucker for small SMDs. I never have the courage to use my fat hand and fingers to solder/desolder SMDs with more than 8 pins. Just now I watch a very good video on how to make a cheap vacuum sucker. I have all the components in my junk box. I guess I should DIY one, and practise 8pin SMDs, and show my bad friends a video so that they would begin to respect more than I deserve. Ref DIY vacuum sucker: https://www.youtube.com/watch?v=qJWUUK1s_G0 – tlfong01 Aug 19 '20 at 14:45
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    The way I heard it was, that besides giving a surface for the pick-and-place machine, it add a bit of protection, for the plastic inside the USB socket, from the heat of the (IR-)reflow oven. – Gerben Aug 19 '20 at 14:53
  • @gerben plenty of usb sockets that don't have a pick and place pad that are still wave soldering compatible. – Passerby Aug 19 '20 at 16:20
  • @Gerben wondered about that too - connector plastics tend to melt to death in situations where even your semiconductors still laugh... – rackandboneman Aug 19 '20 at 17:25
  • Reflowable connectors use more heat resistant plastics than connectors that are only designed to tolerate hand or wave soldering. They are still much more heat sensitive than most components though. – Peter Green Aug 20 '20 at 01:22

2 Answers2

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The official name is Pick and Place Pad. While this can refer to hard parts added to bigger or irregular shaped parts for pick and place, it also refers to the tape used for picking.

The tape a high heat, non-conductive tape, used for pick and place machine tips to suck onto to place the connector on a board. It may be Kapton, a name brand Polyimide tape, or may be an alternative brand and type tape. Others use Mylar for example. It just needs to survive movement and typical wave soldering or other automated SMD soldering solutions.

From a manufacturer data sheet: https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1-1773973-2_Mini_USB_Connectors&DocType=DS&DocLang=EN

enter image description here

For another one, Mylar tape specifically.
http://www.assmann-wsw.com/fileadmin/datasheets/ASS_1456D_CO.pdf
enter image description here

And another: http://www.elstore.it/wp-content/uploads/prodattach/CU04SCM15B0-R0-LF.pdf
enter image description here

It's not intended or required to be removed, as it neither affects the part or usage.

Molex added them onto larger parts since manufacturers/assemblers have moved away from older pick and place mechanical grippers to vacuum pickers. They specifically use Kapton brand tape, cause you know, Molex is big business:

“By adding a Kapton tape surface to the top side of the connector, the Vertical SMT Modular Jacks from Molex can be picked and placed by vacuum heads, delivering a faster, more cost-effective method which is in line with other SMT components in the assembly process.”

https://www.businesswire.com/news/home/20141202005123/en/Vertical-SMT-Modular-Jacks-Molex-Kapton-Tape

And you don't even need straight from the factory parts with this pad on them. This can be added on after the fact, by using tape dots. Great for automating a process. https://smtnet.com/Forums/index.cfm?fuseaction=view_thread&Thread_ID=17372

Issue: A PCB assembly company found themselves with thousands of SMT connectors in inventory, on reels, ready to place. But their pick-and-place equipment was unable to pick them up because of gaps and irregular features on the tops of the connectors.

Solution: NuWay was able to open the carrier tape, apply an adhesive Kapton pad to the top of each part, re-seal the carrier, and rewind the reels. The adhesive pads were circles and rectangles kept in stock at NuWay for just this purpose. The turnaround was fast, and helped the customer make use of thousands of dollars of otherwise unusable connectors.
https://www.nuway.net/solutions

Passerby
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It's to give the pick and place machine a flat surface to pick it up by, when it's transferring the part from its tape to the PCB.

The Photon
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    And I guess most suppliers remove this tape, but some are lazy and leave it on? – Intrastellar Explorer Aug 19 '20 at 02:35
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    Well if you want to remove the tape, you have to pay somebody to do that. When removing it is not necessary, leaving it on is just the less expensive option. – Vladimir Cravero Aug 19 '20 at 06:11
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    @IntrastellarExplorer no, because it's sometimes an added cost to order pick and place compatible parts, or they have different p&p machine types so don't need a vacuum gripper compatible part. The ones that don't have the tape, most likely never had the tape. See my answer. – Passerby Aug 19 '20 at 06:14
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    Wouldn't it be more accurate to say it gives a smooth airtight surface for vacuum pickup, rather than a flat surface? In the connector shown, the surface is already flat, it just has perforations in it. – Jon Aug 19 '20 at 13:32
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    Why remove it? It should not present any risk and removal adds cost, it may of course come off in a washing process, but removal is an extra step. – mckenzm Aug 20 '20 at 04:17
  • @VladimirCravero Or you neeed to add a step in the automated assembly process... which needs a special machine designed to do that job, or a step programmed into an existing machine that will, in either case, extend the assembly time and drive up the cost that way. – J... Aug 20 '20 at 17:57