Final assembly of batch - JLCPCB - Page 1
Forum section: electronics / general

author: Harvs
author_rank: Super Contributor
timestamp: June 09, 2020, 12:16:25 am
content: I've been using the JLCPCB assembly service since in was released to the wider world. It's completely changed my workflow for prototyping.I've just been working on a job which is quite likely to end up needing a small batch of boards assembled in the future, maybe qty 30-50. The thing being there's a few parts which JLC don't have stock of, and a 1mm pitch BGA that they will never fit.For larger volumes, going to a normal PCBA service would obviously make sense.But I'm wondering if others have experience with this kind of 'final assembly' step for batch production using their service?I was thinking maybe making some custom stencils along the lines ofhttps://www.stencilsunlimited.com/quick-turn-rework-stencils-p-81.html?osCsid=adg52htejeojkbvtnkklocrld5for the QFN and BGA. And possibly CNC'ing some sort of jig to drop the board onto pins to align things.Any thoughts on putting the whole board through another toaster over cycle?Thanks

author: ANTALIFE
author_rank: Frequent Contributor
timestamp: June 09, 2020, 12:49:24 am
content: Have you reached out to any Aus PCB assemblers to do the board in one go?I know that Alfatron don't mind doing small runs of PCBA's

author: Harvs
author_rank: Super Contributor
timestamp: June 09, 2020, 02:29:23 am
content: Nope I haven't.But I've had a number of PCBA runs done in the past, and the price and effort required for this sort of small batch of reasonably complex PCBs is in another league.The economy comes from JLC already having 90% of the BoM in the basic parts library, aka already on reels + a completely automated ordering system.

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 09, 2020, 02:59:31 am
content: yeah, by now we only provide ≤30qty for SMT assembly. when we have the next progressive move, we will inform all.

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 09, 2020, 04:52:23 am
content: HiAbout the BGA, the capabilities are no longer the same so you can check our new capabilities from here :https://jlcpcb.com/capabilities/CapabilitiesAbout the missing parts, do you mean the parts are not available to be ordered or the assembly option is not available for some parts!?because you wrote "there's a few parts which JLC don't have stock of" actually JLC don't have components stock since it get it from component supplier LCSC, for further information about your parts you can upload your BOM list in LCSC "BOM tool" to get some details about the stocks before placing any order, here is the "BOM tool" feature link :https://lcsc.com/bom.html#/upload

author: Harvs
author_rank: Super Contributor
timestamp: June 09, 2020, 05:34:28 am
content: Quote from: JLCPCB Official on June 09, 2020, 04:52:23 amThanks, for the capabilities update. I understand your PCB's are capable of the BGA's, as I am using them currently and hand place the BGA chip. However you don't have the part on your parts list, so I can't order:https://lcsc.com/product-detail/CPLD-FPGA_XILINX_XC6SLX16-2FTG256C_XILINX-XC6SLX16-2FTG256C_C39313.htmlFor the other parts, there are some that LCSC have in stock (although not a lot), but no stock showing at JLC:https://lcsc.com/product-detail/Digital-Isolators_Analog-Devices_ADUM1400BRWZ-RL_Analog-Devices-ADI-ADUM1400BRWZ-RL_C72910.htmlhttps://jlcpcb.com/parts/componentSearch?searchTxt=ADUM1400BRWZ-RLAnd for another part there's zero stock in both sites:https://lcsc.com/product-detail/Analog-To-Digital-Converters-ADCs_Analog-Devices-ADI-AD7779ACPZ_C398822.htmlhttps://jlcpcb.com/parts/componentSearch?searchTxt=C398822At the moment, the 30 piece limit hasn't been an issue. Far more of an issue is stock levels.From what you're saying, it sounds like you can place an order requiring parts that are in stock at LCSC but showing zero stock on the JLCPCB parts site? I don't think this is possible with your current site, it doesn't allow you to select a part that doesn't have enough stock?Thanksedit: wrong link

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 09, 2020, 07:35:17 am
content: Yes you are right, I just checked the issue, I will report this to the technical team to update it so please could you provide me links of all your parts that have available LCSC parts and 0 stock in JLC ? this will help both of us to update the info.Thank you.

author: Harvs
author_rank: Super Contributor
timestamp: June 09, 2020, 10:55:31 am
content: I have no more parts on the last order that fit this category, but it is really quite wide spread.I have a small script to scrape your parts page so I can sort by parts with a minimum stock level. I pulled the Digital Isolators section, uploaded the first 200 records into the LCSC BoM tool, downloaded the results and compared the two.Out of 200 lines, the attached CSV file has 39 lines which show zero stock at JLC and some stock at LCSC. In most cases very low stock, but in some cases quite a bit.

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 09, 2020, 11:28:00 am
content: Thank you for these information, it will help

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 12, 2020, 03:25:53 am
content: Yes, the stock problem always haunts you guys. In fact, it is the same for us. We have consulted electronic engineers on how to improve the shortage of parts library and update the types of parts. Many of our leaders are electronic engineers. They understand what you guys worry about and are conceiving various methods. As we know, although JLCPCB and LCSC are brother companies, the inventory is also derived from lcsc, but the two companies operate independently, meaning that jlcpcb cannot use 100% of lcsc parts. Many customers report that lcsc is clearly in stock, then why can't it be used in JLCPCB SMT services? This is the reason. At the beginning of this year, our CEO put forward the idea of pre-order parts. Customers can order in advance. This method can be more convenient for engineers and ourselves. It has not yet been implemented. I really appreciate your suggestions and feedback.

author: Harvs
author_rank: Super Contributor
timestamp: June 12, 2020, 09:30:11 pm
content: The order in advance concept certainly has merit.Personally it would really depend on how long in advance I would need to order, what (if any) additional cost would be involved? I understand you're probably targeting batch production with this idea, but what sort of minimum order quantity would you be willing to get parts in from LCSC? E.g. would you get parts in to assemble 10 PCBs?The vast majority of PCBs I order for work are 4-layer. This means there's generally a 4 day turn time on the PCB before assembly can start anyway. Would it be possibly to get parts from LCSC during this time?

author: uer166
author_rank: Super Contributor
timestamp: June 12, 2020, 10:08:01 pm
content: The pre-order in advance idea is genius. I'm willing to pay a premium for insuring that I can order parts that aren't currently in stock. It would also be much more comfortable for parts thatarein stock, since to get them (in case stock is depleted), I just need to pay a bit more $ in advance.

author: Harvs
author_rank: Super Contributor
timestamp: June 15, 2020, 05:01:59 am
content: @JLCPCB OfficialCould you include the option to lay solder paste on all SMD pads during the assembly process, and not just the pads of the components your assembling?I'm up to maybe 10th PCB where I'm adding a QFN device after your assembly, and it would cut the time in half if the pads were already bumped with solder.Thanks

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 16, 2020, 09:39:55 am
content: Quote from: Harvs on June 15, 2020, 05:01:59 amBy now we can't. The areas where have solder paste must be placed with SMD

author: OwO
author_rank: Super Contributor
timestamp: June 16, 2020, 09:51:53 am
content: I think the reason is because they generate their own stencil file based on the parts you are actually placing, and for parts on the BOM not matched to a library part they don't know how to generate the stencil openings. They don't use the user provided stencil file to avoid stencil design related soldering issues. One possible solution is to use the user provided stencil design for areas that are not JLC placed. The software could start from the user stencil file, and delete openings on parts that will be JLC placed, and then add JLC designed openings for those parts.

author: Harvs
author_rank: Super Contributor
timestamp: June 16, 2020, 10:37:29 am
content: I'm sure you're right about JLC generating their own stencil file for assembled pads.But AFAIK if you order a stencil with a bare PCB, and not a separate stencil order, they actually generate the stencil off your board copper layers and ignore your stencil file (it's been discussed here before.) So that's pretty much what I'm asking them to do with the assembly process. I think it's just a process limitation, not a technical limitation of their software tools.

author: wraper
author_rank: Unknown
timestamp: June 16, 2020, 10:44:35 am
content: Quote from: Harvs on June 16, 2020, 10:37:29 amWhen I ordered stencil together with PCB, I asked them in a comment and they made it according to stencil file. Dunno what they do by default, though.

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: June 20, 2020, 04:09:30 am
content: Quote from: wraper on June 16, 2020, 10:44:35 amdear sir, do you mean by you just want to order a plain stencil, no design with it?