How might PCB be damaged in  production? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: August 17, 2022, 01:17:42 pm
content: Hi,We ordered a PCB from a small supplier and they said because it is 495mm x 185mm it may get damaged during production. They are making 5 of them for us.Do you know what kind of damage they are referring to?The board is 4 layer. It is a simple SMPS board. Min space = 0.3mm, Min drill = 0.6mm.Copper = 1oz all layers.Thickness = 1.6mmI wonder if we had ordered it with 0.5oz inner layer copper things would have been ok?Anyway, it sounds like they just wonrt ship the board if it is damaged?...but will give us a coupon instead.This is what they said....(we asked them the questions but they havent got back yet)Quote

author: temperance
author_rank: Super Contributor
timestamp: August 17, 2022, 01:43:53 pm
content: Board rigidity it not defined by copper weight but more about the amount of glass fiber.Why don't you ask your supplier those questions? They know their machines and materials and we don't.Do you agree with this simple observation?

author: Jackster
author_rank: Frequent Contributor
timestamp: August 17, 2022, 01:50:49 pm
content: Scuff marks from panels rubbing are pretty common with lower-end (cheaper) manufacturers.We see this a lot from the likes of JLCPCB for example.Actual damage to traces or pads that would void the board/panel can happen due to mishandling or alignment issues when making each layer and general quality issues derived from the quality of the production line.Sometimes boards warp due to bad storage, being dropped or some material defects. Less common, more typicall in transport when they vacume them.Poor handling can lead to damaged edges and corners. Less of a problem with rails but even so, this should not happen.QuoteReally they should just run that panel again to get you the 5 boards you ordered. If you only need one or two of them then yea, take the coupon.But really, if you order 5, you should get 5. This is them trying to save money on a 6th panel. Granted the smaller quantity orders like 5-10 boards, there is not much if any money in it for them.We sometimes get 1-5 extra boards from the manufacturer if they have had to run the panel again due to one or more boards within the panel being bad.Do share who you are using. Someone might have more insight into their process and quality.The board being X size should not matter. More concerned about the quality of their production line if thin longboards are a problem for them...Sounds like they are not too confident in it themselves.

author: SMTech
author_rank: Frequent Contributor
timestamp: August 17, 2022, 01:57:49 pm
content: Its sounds like they are risk/cost averse to having your PCB take up such a large proportion of their multi-design panel to me, bit like a silicon defect affecting yield in a wafer. I don't think we've ever had that kind of response from PCBWay and we order larger than that. (also since when was 250*200 large?)Curiosity would ask who this manufacturer is?

author: jmelson
author_rank: Super Contributor
timestamp: August 17, 2022, 02:55:18 pm
content: Quote from: Faringdon on August 17, 2022, 01:17:42 pmYou need to find a better fabricator for your boards. This outfit is a hack! They can't guarantee they can produce a board for you!Jon

author: IconicPCB
author_rank: Super Contributor
timestamp: August 18, 2022, 12:02:44 pm
content: Since it is a multilayer board their tooling/inner layer registration setup may not necessarily guarantee proper layer registration across the width of a full panel.

author: Faringdon
author_rank: Super Contributor
timestamp: August 24, 2022, 05:05:22 pm
content: If you want a cheap 4 layer PCB, and really you want 1oz on all 4 layers.........is it true though, that the far cheaper and more common option is 1oz outer, 0.5oz inner?........and the 1oz inner needs the 0.5oz inner to be plated up to 1oz, and as such involves an extra production step which may result in mistakes in the board due to eg alignment problems?

author: floobydust
author_rank: Super Contributor
timestamp: August 24, 2022, 08:49:34 pm
content: A near 500mm (19") PC board with 1.6mm laminate and lots of heavy through-hole parts is simply going to flex to much and break thingsDuring handling, assembly etc.You have to go thicker, stop being cheap. I use double (1/8" or 3.2mm) thickness laminate. As well as base 2oz copper for the outer layers, with your expected high currents.Misalignment due to extra copper plating is the least of your worries I think.

author: Faringdon
author_rank: Super Contributor
timestamp: August 25, 2022, 02:45:36 pm
content: QuoteThanks, yes i agree, the latest board is 210mm by 400mm (less than half the size of the previous) and all surface mount PCBs are on "platform" PCBs which are soldered in via thru hole headers. So i have to confess to cheaping it with 1.6mm PCB thickness's, but have taken the further precautions. There are also some 15 "feet" for the board, spread out. Effectively the SMD PCBs are 3.2mm thick as they are 1.6mm PCB on top of a 1.6mm "platform" PCB. They solder to the platform via kind of "legs", like SMD legs, kind of. (there are SMD pads on both "platform PCB" and "SMD PCBs"), for these "legs").

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 25, 2022, 04:01:46 pm
content: Usually, pooled proto services make just enough panels, cut them out, inspect and ship. Whichever parts either aren't needed by the customer (ordered less qty) or fail test (due to whatever reason, poor photography, blemishes, torn/cracked foil, blisters, gross breakage..), those are simply discarded.Sometimes you'll be shipped the extras, because yield was better than average and, hey, why not, they have no use for them.Have heard of one customer receiving a few panels worth (custom panelized build not proto in this case), that returned more units than ordered; the extras were just marked with big black 'X's, but were otherwise perfectly serviceable.1oz sounds quite thin for the power levels you're working at. Maybe that's okay, it's 4 layers; others have managed with less before (say 1oz 1-layer, albeit usually at lower power levels; still, have seen that up to, what, 500W or so?). But that's very much another warning sign, you may want to put more consideration into the layout and stackup of the board, along with, y'know, everything else in your design. And, budgeting accordingly.Tim

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 25, 2022, 05:52:03 pm
content: They probably mean that they may have some panels that fail bare-board test, higher probability on a larger board. They will usually refund for any bad panels, but that may not help if you really need all of the panels.