Smd 0402 / 0603 assembly considerations - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: January 09, 2020, 11:12:05 am
content: Hi all,Newbie question. What questions or considerations should I be aware of if I want an assembly house to pick n place really small parts? 0402 / 0603 (metric I think). Sizes such as 0.5mm x 0.25mm leds.Do pnp machines not care? are nozzles small enough? Does it matter the spacing between components?Essentially what questions should I ask the assembly house? Or what documentations should I find on their spec pages?

author: Berni
author_rank: Super Contributor
timestamp: January 09, 2020, 11:21:14 am
content: Any modern pick and place house should be able to handle 0402 these days.Pick and place machines grab parts from the top anyway so no special spacing requirements. Its mostly just the typical stuff of getting your footprint correct so that you don't get too many failures in the form of components shifting out of place, lifting up on end etc... These sort of 'thombstoning' problems tend to be more common with tiny parts.

author: made2hack
author_rank: Frequent Contributor
timestamp: January 09, 2020, 11:57:32 am
content: okthx. Who has precedence in design rules? The pcb house? Or the assembly house? Or do they tend to be identical? (ie min trave width, spacing, etc)

author: mvs
author_rank: Frequent Contributor
timestamp: January 09, 2020, 12:12:57 pm
content: Quote from: made2hack on January 09, 2020, 11:57:32 amTrace width/spacing is important only for PCB fab. Assembly house is more interested in component clearance / rotation, pad dimensions, thermals, pcb panel size, rails, feducials, etc.Dave has some videos about design for manufacture on youtube.

author: Berni
author_rank: Super Contributor
timestamp: January 09, 2020, 12:31:01 pm
content: Its the PCB house that is actually manufacturing your board so they say what they can produce. Tho its mostly a matter of what is cost effective for you rather than what they can do.A lot of PCB houses will do 0.075/0.075 mm track/space with 0.1mm holes and 16 layers. But expect a small prototype run of 5 boards to cost you about 1000 to 5000 USD. The larger features and tolerances you can have the cheaper the board is going to be. Meet the lowest spec dimension rules and you can get 10 boards made for <5 USDAll that matters for the assembly house is that you provide them with good documentation. Having components consistently rotated in libraries, good descriptions and part numbers, well organized BOM, assembly drawing printouts for them to double check. Even a 3D render of both sides of the board can be helpful to them (If your CAD tool has 3D support). The easier you make it for them the less time you are going to waste talking to them and explaining stuff and less likely its going to be they are going to assemble your board wrong.

author: made2hack
author_rank: Frequent Contributor
timestamp: January 09, 2020, 12:40:43 pm
content: Ok. Thanks everyone.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: January 09, 2020, 11:12:05 pm
content: Quote from: made2hack on January 09, 2020, 11:12:05 amJLCPCBdo notassemble any parts smaller than 1005. PCBWAY support down to 0402. The team making one of the recent conference badges ran into trouble due to designing with small parts and then having a limited choice of PCB houses ... it ended up costing them more.So it's a good idea to check if your preferred manufacturer can even do it in the first place. And ask yourself if it's really necessary ... Don't do it just for bragging rights.

author: Berni
author_rank: Super Contributor
timestamp: January 10, 2020, 06:24:00 am
content: Quote from: I wanted a rude username on January 09, 2020, 11:12:05 pmWhat 1005?! So JLC won't even assemble 0805 sized passives? Even 0805 is considered pretty large these days so that makes there assembly service pretty useless. Who still uses 1206 parts these days?But if they only do such large passives, can they then even do chips with 0.5mm pin pitch?EDIT: Oh 1005 is the metric size for 0402. So JLC does assemble 0402 and that sounds reasonable since anything smaller starts getting ridiculously tiny.

author: Nerull
author_rank: Frequent Contributor
timestamp: January 10, 2020, 06:52:59 am
content: Whoever decided that smd components should have two completely different but identically formatted unitless size identifiers should be slapped.

author: Berni
author_rank: Super Contributor
timestamp: January 10, 2020, 08:43:17 am
content: Quote from: blueskull on January 10, 2020, 07:35:39 amI also see it never being used hence why it confused me so much when someone suddenly did use it.Horrible idea these metric smd sizes.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: January 10, 2020, 09:21:31 am
content: "The nice thing about standards is that you have so many to choose from." -Andrew S. TanenbaumI'm all for consistency. Older SMDs were specified in imperial, e.g. 2512 imperial (which would be 6332 metric), but that flipped at some point and newer packages like 5050 LEDs are specified in metric. Same happened with ICs. Presumably it will all metricate eventually ... made2hack and I are just helping the process along.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 10, 2020, 09:28:20 am
content: Quote from: Nerull on January 10, 2020, 06:52:59 amThere wouldn't be any issue. They are primarily names, i.e., identifiers, not measurements. They uniquely convey the meaning of the correct footprint, which can be looked up.Anyone who uses the "metric" versions is just so totally and utterly misled that they must be ignored. Usage of "metric" version is, luckily, almost nonexistent.Creating a new standard is not a big issue, because a new standard has a new name. Creating a new standard and borrowing a name of the old is just totally nuts.There is a reason people say "1 kg", not "1 lb (metric)", or just "1 lb" (assuming metric without saying anything). There is no metric lb, similarly there is no metric 0402. Whoever says otherwise is either completely nuts, or has a malice intent to confuse, and is not suitable for engineering.Any manufacturer is free to come up with a new, descriptive identifier for SMD components, and use metric system for that. For example, "0.4x0.2mm" would do the job pretty nicely; or "M004002" would work with 0.1mm resolution up to 99.9x99.9 mm without any dot characters if that's a problem.