Panelisation question. - Page 1
Forum section: electronics / general

author: DTJ
author_rank: Super Contributor
timestamp: November 09, 2016, 03:26:54 am
content: I need to order some PCBs panelised so I can have an (Australian) assembly house put the boards together for me.I'm getting the boards through PCBCart (I'm happy with quality & cost).I've considered calling a couple of assembly places and asking them what they prefer but that may mess things up when I try to get assembly quotes from3 or 4 different places.For Australian assembly if that's relevant.Looking at a few PCB manufs they talk about 12"x24" panels when I've only ever worked with smaller say 10"x12" panels in the past. Is size solely up to the user?I assume I'll have to supply a framed solder paste stencil - are there standards for this?What critical things do I need to know so I don't end up with panels the assembly house can't use?Cheers.

author: DerekG
author_rank: Frequent Contributor
timestamp: November 09, 2016, 04:01:12 am
content: Quote from: DTJ on November 09, 2016, 03:26:54 amAsk the assembly shop:1/ The max panel size their SMD robot can handle;Ask what hole size they want on the outside of the edges of each panel for mounting on the bed of their SMD robot & where they want them;Ask if they require any fiducial marks on each circuit;Ask what colour solder mask they prefer to operate with their automated visual inspection systems;2/ The max panel size their SMD reflow oven can handle;3/ The max panel size their wave solderer can handle;4/ The max panel size their manual assembly frames (if there are components that need to be hand mounted) can handle;5/ The solder paste stencil overlap required on each side for mounting in their frames;Ask what thickness they want the solder paste screen. Often Chinese suppliers will try & give you 0.1mm or 0.15mm thick stencils, whereas 0.2mm is often preferred to ensure enough solder is layed down on the pads;6/ Ask the setup cost for each run. This will help you choose how many boards to run each time.Hope this helps.

author: DTJ
author_rank: Super Contributor
timestamp: November 09, 2016, 04:40:09 am
content: Hi Derek, thanks for going to the trouble of giving me such a comprehensive reply. Much appreciated.Are you saying that an unmounted paste stencil is ok and they will mount it into their own frame when applying the solder paste?I checked a few local assembly places thinking they would put this info on their webpages but there's absolutely nothing.Based on your suggestion I think I'll just email a couple of places that I'm likely to use and see if I can put together a solution that can be used by both.Thanks again.DTJ

author: janekm
author_rank: Unknown
timestamp: November 09, 2016, 05:45:44 am
content: For the stencil, you just have to ask, as it depends on what kind of stencil printer they use. If it's anything like the UK they may have a stupid stencil printer that uses a custom arrangement of mounting holes making it really hard to order the stencil from anyone who isn't set up for that (i.e. you won't be able to order the stencil yourself and it will be crazy expensive).In China everyone has standardised on aluminium framed stencils so this problem doesn't really occur.All the same the kind of stencil you need depends on what kind of components you have. If everything is >0603 and >0.6mm pitch LQFP then 0.2mm stencil may be ok. For anything below 0.5mm pitch QFN you definitely need a 0.15/0.1mm thickness stencil, and with electropolishing as otherwise the paste won't release from the stencil properly. That's another reason most assembly houses prefer to order the stencil for you, it's a lot of trouble for them if you order the wrong kind of stencil and they have to explain to you why they can't use it.

author: Kean
author_rank: Unknown
timestamp: November 09, 2016, 06:44:07 am
content: In my experience, the panel size is mostly up to you within the upper and lower limitations of their equipment. Better to avoid it being too big in case you wish to switch to another assembler later with different limits. They will also often have preferred max sizes depending on PCB thickness, and maybe some specific requirements around the edge rails, fiducials, and holes. They can often work around these, but it may cost extra due to more manual handling.As mentioned by others above, the stencils are often best left to them, although it is worth asking because you could save a lot of money.

author: DTJ
author_rank: Super Contributor
timestamp: November 09, 2016, 09:10:43 am
content: Thanks Jane & Keam, it really sounds like I need to have a chat to them. Thanks for the tips on the masks.

author: DerekG
author_rank: Frequent Contributor
timestamp: November 09, 2016, 11:13:41 am
content: Quote from: DTJ on November 09, 2016, 04:40:09 amThe freight cost from China will be less for an unmounted solder paste screen (stencil) as the mounting frame adds to the overall dimensions quite a bit.Solder paste screens from China often cost as little as US$30 or $40 each for a mid to large size panel. I have ordered them with prototype & production boards quantities from PCBWAY. The last few orders of boards contain SMD mosfets carrying some 20A to 30A. Hence the request for 0.2mm screens. Generally PCBWAY offer stainless steel screens, however there is nothing wrong with brass screens if you are going to manufacture (say) less than 50,000 panels. Brass screens are often easier to work with.Solder paste screens supplied in Australia will generally cost you $400 to $600 each. Just ask the board assemblers for a PDF of the screen size they want to work with. The PDF should also show what mounting holes etc are required. Simply then pass that on to the Chinese supplier. Not difficult at all.

author: Kean
author_rank: Unknown
timestamp: November 09, 2016, 11:29:43 am
content: Quote from: DerekG on November 09, 2016, 11:13:41 amI can confirm that. One of my customers was paying AU$600 per stencil as required by the assembler (now out of business...). They were pretty large unframed stencils, maybe 400x600mm, for panels typically about 165x185mm. Thankfully we had put various designs on each panel, and they etched both paste sides on a stencil, so only 4 stencils were needed across 12 designs. Quite a shock after we'd been getting PCBWing framed stencils for small runs at about US$30 + US$30 shipping.

author: DTJ
author_rank: Super Contributor
timestamp: November 09, 2016, 11:43:31 am
content: There's a bit of bill shock there - I just paid $10 for a stainless stencil for hand assy work and figured I might get away with $80 to $100 for a stencil.....Brass is definitely an option as the stencil will be lucky to see a few hundred passes.EDIT: just checked PCBCartFor a 250mm x 250mm panel a 0.15mm stainless maskunmountedis Australian $30For a 250mm x 250mm panel a 0.15mm stainless maskmountedis Australian $150I'll see what the assy places say.

author: 48X24X48X
author_rank: Frequent Contributor
timestamp: November 10, 2016, 02:20:06 am
content: Some assembly house solder paste dispense machine can only take a fix sized stencil frame. The ones I stumbled upon are usually 550mmx650mm (3 factory in fact).When I brought my 370mmx470mm stencil, the assembly company were laughing, literally saying they were "cute".I got all my stencil off Taobao with frame stainless steel polished 370mmx470mm at CNY98.8 shipped to here Malaysia. That's like $14.5478 with the current exchange rate! Stencil are ready within few hour and if submitted not too late in the afternoon, they ship to my shipping agent the same day. If you are in Australia, Taobao is accessible too. At this rate, even my smallest prototype revision 0.01 has a stencil! So, I have a stack of stencil.What like about their service is, compared to other service provider like the usual Seeedstudio, Elecrow, Smart Prototyping, etc, they are the people that actually manufacture the stencil for you. So, within minutes they will pass me the stencil opening files (they do some adjustment to the opening based on their experience which I think always turn out better than what I initially set) and see if there's anything they were overdoing.

author: DerekG
author_rank: Frequent Contributor
timestamp: November 10, 2016, 03:09:21 am
content: Quote from: 48X24X48X on November 10, 2016, 02:20:06 amYes, they were far too small to be clamped into their frames. You need a certain amount of extra stainless steel around the edges to ensure they can successfully by mounted into the assemblers frame.The assemblers often make a good few dollars by "providing" the solder stencil to you for your job.However, simply demanding a PDF showing the required size, thickness & hole mounting diameters & locations, then pass this on to the Chinese board supplier is pretty easy.

author: Matt-Brown
author_rank: Regular Contributor
timestamp: November 11, 2016, 02:29:55 pm
content: Hi,I work for a contrat manufacurer in the U.S.A and I deal with all the aspects of quoting products we want to bid on ( I mostly do the labor cost).When quoting I look at how big an individual board is (from the gerbers or fab drawing), then work out the best panel for the process. If your board is smd heavy and little to no t/hole it can be paneled into a larger array (out max is circa 355mm x 305mm). I like to keep things sinple and go no larger than 280x190 (sheet of paper) that seems to work best for all of our smt machines, paste, pick and place, optical inspection, x-ray and reflow.Another advantage of this size is processing speed. We can get a panel from one end of the factory to the other faster being about that size. I ahve not seen much difference in cost on the etch between small arrays and larger ones, but larger ones tend to waste more of the board house max array and you pay for cost.Another nice design is wherever possibe have no overhanging parts and nice straight edges and corners. That wayits cheaper for a board house to just do v-score and not have to rout and score. Lastly, always add 3 fids to each board on the panel as well as outer breakaways (we prefer 8 on breakaways 2 at each corner about 5 to 10 mm away from the corner tooling holes.Last advise, let the assembly houses figure it out. They will do this for nothing. At least my company does, we will also work out best stencil thickness and vut for you.Quote from: DerekG on November 09, 2016, 04:01:12 am