0.1mm/0.075mm (4/3 mil) trace width fab options? - Page 1
Forum section: electronics / general

author: Jay1011
author_rank: Contributor
timestamp: June 01, 2020, 12:09:16 pm
content: I'm trying to design with a 9-ball BGA part that has 0.5mm spacing between the balls (a TI TPA2028D1 audio amp if it matters).Per the datasheet, the recommended way to escape the inner ball is with a 75um (3mil) trace. TI recommends 100um (4mil) traces for connecting to the other 8 balls on the perimeter:QuoteI am wondering what PCB fabs to try for these small 3mil/4mil traces. Note that I'm using such small traces on just the one part; the remainder of the board will use the usual 6mil/6mil or better trace width/spacing.This is just for a personal project, and I'm willing to accept the chance that none of these small traces will be fabricated successfully and the boards will be non-functional. Basically, I just want to give it a try, mainly so I can see if I can hand-solder this tiny BGA.I want ENIG for best solderability, so in terms of fab I'm thinking:OSHPark 2-layer, cross fingers because they have 6/6 width/spacing requirements, though my impression is that their fab can do better than thisAisler Beautiful Boards HD, which claims 100um/100um width/spacing is supported, so I'd be violating this only on the one 75um trace to the middle ballSuggestions?

author: Yansi
author_rank: Super Contributor
timestamp: June 01, 2020, 12:12:39 pm
content: The question is then why to drive cost exponentially up just because of one part in the design?I think most of the local PCB houses would be willing to attempt that size of traces. Just ask them and accept the price.

author: asmi
author_rank: Super Contributor
timestamp: June 01, 2020, 12:17:07 pm
content: WellPCB says they can do 3/3 mil traces. Haven't tried it myself yet - though I've done many boards with them with 0.1/0.1 mm traces and they always came out perfect, so I'm reasonably sure they can do 3 mil.

author: Jay1011
author_rank: Contributor
timestamp: June 01, 2020, 12:18:39 pm
content: Yes, there are other parts I could use, but I'm really just trying an experiment here for a personal hobby, not claiming that this is the best part to use.In terms of cost, honestly, I'm hoping to keep the same cost by just knowingly violating trace width/spacing DRCs and yet "get away with it" because of some combination of getting lucky and the fab being able to manufacture better than the fab service is willing to guarantee.

author: Jay1011
author_rank: Contributor
timestamp: June 01, 2020, 12:23:03 pm
content: Yes, I saw WellPCB, but as soon as you move from HASL to ENIG the cost becomes more than using OSHPark or Aisler. They do support 3mil trace/spacing, though, this is a good point.

author: asmi
author_rank: Super Contributor
timestamp: June 01, 2020, 12:38:45 pm
content: Quote from: Jay1011 on June 01, 2020, 12:23:03 pmThe quality of their boards is FAR above and beyond what you get just about anywhere else. Here is example of my recent small board (this is just a 2 layer board). They even sent a core sample along with this board!

author: Drew Fustini
author_rank: Newbie
timestamp: June 02, 2020, 07:13:19 pm
content: Quote from: Jay1011 on June 01, 2020, 12:09:16 pmWe only guarantee our minimum specifications, but our minimum trace width and space specifications are not enforced.You can go smaller than the minimum and often will get favorable results such as 5/5 on 2 layer. The minimum drill is a hard limit as the drill machine has discrete drill bits. Where as, the same LDI machine is used for all boards, so the minimum specifications are really a matter of guaranteed yield.Please feel free to email suppport@oshpark.com - our support team is always happy to help.Thanks,Drew FustiniOSH Park<drew@oshpark.com>

author: soFPG
author_rank: Frequent Contributor
timestamp: June 09, 2020, 10:45:57 pm
content: QuoteI always thought about ordering at WellPCB because of their 3/3 mil trace width and very small via hole size (I don't remember it at the moment) but unfortunately they don't offer a cheap (meaning as cheap as JLCPCB) shipping option - only DHL Express and TNT which are ~35$.After contacting them about this they also said they are not going to offer another way of shipping.Very interesting to see how their boards come out - thank you!

author: KL27x
author_rank: Super Contributor
timestamp: June 09, 2020, 11:01:43 pm
content: I believe anything down to 6-7 mils is done with ferric or cupric. Below that, ammonium/basic etchants practically "have" to be used. So it's a completely different process to have practical yields. Probably why Drew says 5/5 is already pushing it.It will have a much better chance of success if you spec half oz copper.

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 10, 2020, 06:19:10 am
content: Hello ;Talking about supplying you with some good PCB quality, here is the link for JLCPCB production capabilities where you can find details about the BGA capabilities and you can try the service once you find that it suits your needs.https://jlcpcb.com/capabilities/Capabilities

author: daqq
author_rank: Super Contributor
timestamp: June 10, 2020, 07:56:50 am
content: From our local ones, pragoboard (https://www.pragoboard.cz/en/node/27) can do 75um/75um, and upon request 50um/50um

author: soFPG
author_rank: Frequent Contributor
timestamp: June 10, 2020, 09:08:38 am
content: QuoteDo you have details for how much that would cost?

author: daqq
author_rank: Super Contributor
timestamp: June 10, 2020, 09:40:57 am
content: Quote from: soFPG on June 10, 2020, 09:08:38 amNope, sorry. Contact them, they are friendly enough, no minimal order size and can do really funky stuff.

author: asmi
author_rank: Super Contributor
timestamp: June 10, 2020, 01:37:38 pm
content: Quote from: soFPG on June 09, 2020, 10:45:57 pmThe quality of their boards is a whole another level compared to the likes of JLCPCB and other cheap places. They don't race to the bottom, instead focus on quality while keeping the prices reasonable. For example, the board from my previous post was $37 for 10 boards with ENIG and matte black soldermask with yellow silkscreen (I think this combination looks amazing). Even my clients regularly comment on just how great their boards look. Also their soldermask is very durable and withstands many rework cycles with no problems, while JLCPCB boards tend to not fare well on that front. This makes your prototypes look more professional in the eyes of your clients.I think that is why they are not interested to provide cheap-ass shipping options, because they tend to provide crappy customer experience with slow and unreliable delivery. I usually order several different designs at once to spread shipping costs around a bit, but ultimately most of the time I want my boards ASAP and don't mind paying few extra bucks for that. Also most of my boards are 4 and 6 layer, so shipping cost is insignificant compared to their price.

author: soFPG
author_rank: Frequent Contributor
timestamp: June 11, 2020, 11:35:43 am
content: Quote from: daqq on June 10, 2020, 09:40:57 amThey just send me back an offer about 5 PCBs, 50x50mm, 4 layers, 3mil trace width, 0.2mm via hole size:131.5€ (PCBs) + 120€ ("Tooling") + 25€ (Transport) = 276.50€Yeah..no thank you

author: lawrence11
author_rank: Frequent Contributor
timestamp: June 11, 2020, 01:59:38 pm
content: Quote from: Drew Fustini on June 02, 2020, 07:13:19 pmI heard rumors of 6 layer capabilities coming, for many years.Will this ever materialize? There needs to be a 2-6 layer option right here on the continent.

author: Jay1011
author_rank: Contributor
timestamp: June 16, 2020, 04:34:02 pm
content: OP here. Thought I would followup now that I have the OSHPark boards in hand.First, due to distributor stock issues, I ended up using a slightly different BGA part, one with 12 balls in a 4x3 array at 0.5mm pitch, rather than the original plan of a 9-ball BGA with 3x3 array at 0.5mm-pitch. The 12-ball BGA requires the two inner balls each to be escaped with a 75um/3mil trace that routes between two 0.5mm-spaced balls on the perimeter of the BGA.In terms of the OSHPark boards, there's good news and bad news.The good news is that both 3mil traces seem to have been successfully fabbed on all 3 copies of the board.The bad news is that each 3mil trace is shorted to one or both of the two perimeter BGA balls as the trace passes between the perimeter balls. The short is present for all 6 traces (2 traces on each board, 3 boards).Unfortunately I don't have a camera on my stereo microscope, so I'm not able to post a picture of the board. The shorts are reasonably apparent visually, and I confirmed them with a multimeter using testpoints on the board.Oh well, it was worth a try. Out of sheer stubbornness/stupidity, I may try giving Aisler a try with the same board design just to see what happens.

author: mbless
author_rank: Regular Contributor
timestamp: June 17, 2020, 12:27:00 am
content: Quote from: Jay1011 on June 16, 2020, 04:34:02 pmI just use my phone, although, it takes a minute to get the angle right. I'd be interested in seeing the boards if you can manage.

author: PeteH
author_rank: Unknown
timestamp: June 17, 2020, 02:10:25 am
content: You can also distort the pad shapes slightly to get a better spacing between the pads you want to exit between. Oblong the BGA lands slightly and thin them out to get a trace by with better spacing.

author: asmi
author_rank: Super Contributor
timestamp: June 17, 2020, 03:30:47 pm
content: Quote from: Jay1011 on June 16, 2020, 04:34:02 pmNo it wasn't. Going beyond what's guaranteed by the manufacturer almost always end in tears.Take a look at JLC - they guarantee down to 3.5 mil traces on their 4 and 6 layer boards. They are cheap, and the quality is acceptable for the price (don't even hope the solder mask will survive any kind of rework).

author: Jay1011
author_rank: Contributor
timestamp: June 17, 2020, 04:39:37 pm
content: Quote from: asmi on June 17, 2020, 03:30:47 pmIt was worth it to me: $6 for the OSHPark board, with ENIG, and in my hands in 11 calendar days. JLCPCB would be $11 for HASL with arrival in "30-35 working days" or like 6 weeks.Also -- the JLCPCB "Capabilities" page shows 5mil/5mil trace width/spacing for 1, 2, 4, and 6-layer boards. Not sure where you're seeing anything about a 3.5 mil guarantee.https://jlcpcb.com//capabilities/Capabilities

author: asmi
author_rank: Super Contributor
timestamp: June 17, 2020, 05:26:06 pm
content: Quote from: Jay1011 on June 17, 2020, 04:39:37 pmAs long as the board is not much larger than a post mark. What about 10x10 cm one?Quote from: Jay1011 on June 17, 2020, 04:39:37 pmApparently they changed it recently.Herethey still show old values (I've made a screenshot in attachment in case they mess with it too). If that change is their new standard, I won't be ever ordering with them because I need 0.1/0.1 mm trace capability for all but the simplest designs.My apologies.

author: asmi
author_rank: Super Contributor
timestamp: June 17, 2020, 05:35:29 pm
content: Quote from: blueskull on June 17, 2020, 05:30:14 pmTheir solder mask quality kinda blows, so for production I prefer using WellPCB even if they cost extra (client pays for it anyway). On JLCPCB boards if I touch a trace covered by the solder mask with an iron, the mask burns off and I end up tinning the trace. This never happens to the mask used by WellPCB. It is important for me that my prototypes look professional in the eyes of my clients (even after some rework which is typical for prototypes), to me the extra expense is totally worth it. And like I said above, I don't like playing chicken with my boards, because they contain thousands of traces and I will not be checking them all on each and every board manually to see if I won this time around or not.

author: mbless
author_rank: Regular Contributor
timestamp: June 17, 2020, 05:40:34 pm
content: JLCPCB account says it's still 3.5milhttps://www.eevblog.com/forum/manufacture/bga-on-jlc-4l/msg3091703/#msg3091703. From that thread it looks like they got several numbers wrong when switching to the new capabilities format.Quote from: asmi on June 17, 2020, 05:35:29 pmI've noticed this problem with more recent batches. I don't remember having this problem before.

author: asmi
author_rank: Super Contributor
timestamp: June 17, 2020, 05:52:45 pm
content: Quote from: mbless on June 17, 2020, 05:40:34 pmYea I don't know either if it became worse or always been that way, because usually I don't have that much of a rework. However my most recent order with them is a 4 layer RF board, and wherever there is RF, there is always a ton of rework to tune things. I ended up having several lifted pads, even though I was desoldering-resoldereing using hot air gun specifically to protect traces from damage.

author: phil from seattle
author_rank: Super Contributor
timestamp: June 17, 2020, 06:05:02 pm
content: Quote from: mbless on June 17, 2020, 05:40:34 pmI've only been using JLC for about 3 months but all the PCBs I've bought from them suffer from this. Also, the mask seems fairly fragile - easier to scrap off. In the past I've used OSHPark, PCBWay and AllPCB - none of their solder masks are easily burned or fragile. I don't see this as a big problem when using JLC's assembly service though it does mean you have to be extra careful when reworking a board.

author: soFPG
author_rank: Frequent Contributor
timestamp: June 18, 2020, 08:55:23 pm
content: Could this be because they are now offering 4 Layer PCBs for 5$?