Design considerations for a slot in PCB to solder another PCB vertically - Page 1
Forum section: electronics / general

author: davorin
author_rank: Unknown
timestamp: February 27, 2025, 04:55:16 pm
content: Good evening (o;Not sure if the title is clear enough as I am not a native english speaker (o;What are the design considerations for creating a slot on a base PCB to solder onto it another PCB like the ESP-02S module?Let's say the width of the solderable PCB is 1.6mm thick and 20mm wide...do you make the slot in the PCB software 1.7mm thick and 20.5mm wide? And I assume the solder pads have a minimum distance to the edge as well?Or does this depend on the PCB manufacturer?Search on the pcbway website but didn't find anything...

author: shabaz
author_rank: Frequent Contributor
timestamp: February 27, 2025, 05:10:29 pm
content: Funnily enough I just did that recently. It has some significant limitations. Depends on manufacturing tolerances too, of course. And you'll always have a copper gap for solder to bridge (which can be fine for very cost-sensitive applications).If you really want to install at right-angles (and it would depend on the antenna - you'll need to check the datasheet), then personally, I think you'd be far better off creating a small carrier board, and solder it flat onto that, and then use a right-angle pin header; this would be far more cleaner.

author: Kean
author_rank: Unknown
timestamp: February 27, 2025, 07:16:36 pm
content: In the case of the ESP-02S, you will find a recommended footprint & cutout in the datasheet - although it maybe depends on the source of the module/datasheet.It uses a 0.8mm thick PCB and they seem to recommend a 0.76mm wide slot that is 11.8mm long.Seehttps://wmsc.lcsc.com/wmsc/upload/file/pdf/v2/lcsc/2401121831_DOIT-ESP-02S_C19949060.pdfJLC also have the part in their EasyEDA library with a pre-defined footprint so I would suggest checking that out for dimensions as well.https://jlcpcb.com/partdetail/DOIT-ESP02S/C19949060

author: langwadt
author_rank: Super Contributor
timestamp: February 27, 2025, 09:13:04 pm
content: Quote from: Kean on February 27, 2025, 07:16:36 pmmakes no sense, how is a 11.8x0.8mm pcb going to fit in a 11.8x0.76mm hole?

author: thm_w
author_rank: Super Contributor
timestamp: February 27, 2025, 09:42:14 pm
content: Yeah something is off, they also call it a v-cut, but, you don't have v-cut unless its across the whole board.There is a design here:https://oshwlab.com/ashp/esp-02s-debug-extension-adaptor_copy_copyAnd an AI thinker module here:https://item.szlcsc.com/2895542.htmlWhere they have a 0.8mm PCB and a 0.9mm slot which sounds reasonable.They even add castellations to it to make it more rigid.

author: tooki
author_rank: Super Contributor
timestamp: February 28, 2025, 12:02:02 am
content: Quote from: davorin on February 27, 2025, 04:55:16 pmWhile a little tiny daughterboard like this is probably the best-case scenario for such perpendicular board-to-board soldering, it’s an approach I would avoid if at all possible. It’s one of the less reliable construction methods, especially if any forces are ever applied. (It is understandably tempting to use it for front panel boards, to join them to a main PCB, but it’s very common for these combinations to fracture in use.)

author: Kean
author_rank: Unknown
timestamp: February 28, 2025, 04:24:46 am
content: Quote from: langwadt on February 27, 2025, 09:13:04 pmQuite tightly I guess...I was just pointing to some resources, I've not tried these myself. The mention of V-cut also worried me, which is why I thought looking at the footprint in EasyEDA might give better info as it has maybe been tested... maybe...With such a small mass with a small moment of inertia , I suspect it would take a lot of force to fracture the 18 solder joints. These modules are used in a lot of IoT devices, mind you cheap ones which probably no one worries too much about throwing away. More annoying would be the labour of manually soldering the modules, and why a tight fit may be preferable. Else it would need a special made jig to hold it during soldering.

author: thm_w
author_rank: Super Contributor
timestamp: February 28, 2025, 11:00:44 pm
content: Quote from: Kean on February 28, 2025, 04:24:46 amIts alright, I think the easyeda footprint is based off the ai thinker datasheet which is really professionally done.Can find photos of a similar module here:https://www.aliexpress.com/item/1005005777409596.html

author: Kasper
author_rank: Frequent Contributor
timestamp: March 02, 2025, 05:47:31 am
content: Quote from: Kean on February 28, 2025, 04:24:46 amMaybe by 'v-cut' they mean countersunk. That could help the 0.8mm fit into the 0.78mm.Side note: thickness tolerance is +/-0.2mm. You can pay extra for +/- 0.1mm though so you may be cramming a 1.0mm PCBWhen I'm worried about a fractured solder joint, I solder a wire in it.