Aisler manufacturing tolerances - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: October 03, 2020, 08:59:52 am
content: I burned myself on a PCB design as I did not pay close attention to the manufacturing tolerances and just assumed the 0.1mm was valid all round. The PCB came out with mysterious untraceable shorts only after re-flow soldering. So I looked carefully at the specs having dug them out from the depths of their website and saw the errors I had made.But what I have a problem with is that Aisler states on the site and have stated in emails that these are the absolute limits and they encourage people to give a bit more leeway:Please also note that these rules are the bare minimum that we support. If you can leave some safety margins in your design, the PCBs will be more likely to work the way you intended them to.I'm sorry? they don't guarantee the limits and I have to figure out what they are? Am I justified in being incredibly uncomfortable with this? This is coupled with the fact that they do not check the designs before manufacture. You just get what you get.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 03, 2020, 09:33:23 am
content: Yeah, that's a very odd and unprofessional way to put it. Normally they give the minimums which areguaranteedto work, and then, depending on the place, they may or may not give you the possibility to go below these limits with your own risk.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 03, 2020, 09:48:42 am
content: Quote from: Simon on October 03, 2020, 08:59:52 amseeed will charge $80 more for this tolerance (4 mil), so i keep using the cheap way (6 mil) but then i will not go to that figure, something like 0.2mm (instead of minimum 0.15mm) i will use, if one day i need guaranteed 0.1mm, maybe i will use more expensive seeed package or find another more expensive manufacturer that can spec half that.. btw i cant see the trace width spec in aisler website, so thats not a good sign imho...https://aisler.net/help/design-rules-and-specifications/specifications

author: Simon
author_rank: Unknown
timestamp: October 03, 2020, 09:55:05 am
content: As much as I like them they seem to live in a bubble and think that just because they have plenty of customers (because they are cheap) they are doing it all right. Fact is they seem to do everything different and when I point it out claim that this is what others do when this is not the case. So I have a credit account with them for work. But it was only because i complained that they added some convoluted way after the order was already made to put an order number in. My employer like many others matches invoices to orders based on err order numbers and will only pay an invoice that matches an order. Aisler will only allow you to order one design at a time. This means that there is an invoice for every design even if done with the same order number which means our accounts department has to make separate payments for each invoice and has more paperwork to handle than needed. They just don't seem to have a clue about general business practices and for my own business it is a pain in the ass to have to file separate invoices matching them to separate payments doing more work. So i ordered 4 boards at the same time. instead of one invoice and one payment I had to process and record 4 (along with 4 currency conversion fees). In business time is money and the cost of dealing with them is higher.

author: Simon
author_rank: Unknown
timestamp: October 03, 2020, 09:57:45 am
content: Quote from: Mechatrommer on October 03, 2020, 09:48:42 amThis is the top secret buried specification page:https://aisler.net/help/design-rules-and-specifications/2-and-4-layer-design-rulesthey state 0.1mm trace, so in my current design I have used 0.12mm where i need to squeeze some traces in through a gap but tend to stick to 0.25mm.

author: Simon
author_rank: Unknown
timestamp: October 05, 2020, 01:19:58 pm
content: what I don't understand is why traces can be 100µm apart but traces must be 200µm from copper zones, what is the difference?

author: Siwastaja
author_rank: Super Contributor
timestamp: October 05, 2020, 02:30:25 pm
content: Quote from: Simon on October 05, 2020, 01:19:58 pmHaving done quite a bit of etching and processing, down to areliable6/6 mils, I have an idea: traces overetch a bit, because having copper to be etched away locally heats up and mixes the etchant. In poorly controlled home process, this means that a 6-mil trace "all alone" with no other copper features nearby may be overetched away completely. Conversely, a track over a large copper pour area, with minimal clearances to the plane, does not overetch at all. When the etching time it adjusted to get "overall good" result, it's even possible itunderetches, i.e. the clearance between the plane and track end up being less than designed. I managed to minimize such problems with very vigorous bubbling (aquarium pump is far from enough).In a professional setting, artwork compensation algorithms are likely used to pre-distort the customer gerbers. Yet such limitation may still remain in the specifications.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 05, 2020, 02:32:18 pm
content: manufacturing specific... maybe something to do with this (etch factor)https://www.7pcb.com/blog/how-etch-factor-affects-trace-width-and-spacing.php

author: Siwastaja
author_rank: Super Contributor
timestamp: October 05, 2020, 02:37:35 pm
content: Etch factor relates more directly to the fact that you can't do as fine tracks and clearances on a thicker copper, hence many fabs that do 6/6 mils normally, limit it to 8/8 mils on 2oz copper.In a home-brewn process, I limited myself to 8/8 mils on 1oz copper and used 0.5oz clad for 6/6 mils designs. Professional etchant solutions and tanks are definitely better than this and can do reliable 6/6 mils easily on 1oz copper.

author: Simon
author_rank: Unknown
timestamp: October 05, 2020, 03:50:09 pm
content: Right, I thought there may be some process reason why.

author: Simon
author_rank: Unknown
timestamp: October 10, 2020, 10:33:04 am
content: I've decided to give Aisler a miss this time. I will use PCB train instead who have similar and simpler tolerances (although i had to get full details by email). My problem with Aisler is that they will not check the files first and just make whatever. I have had PCB's that pass electrical test at Aisler but after re-flowing develop mysterious shorts. This was probably my fault as I got some of the tolerances wrong but had they checked them they would not have manufactured in the first place. Because they refuse to give any definitive answers I am not going to risk a time sensitive project and have no intention of building twice.