PCB stacking - Page 1
Forum section: electronics / projects

author: sirhaggis
author_rank: Regular Contributor
timestamp: September 11, 2016, 03:31:17 am
content: Hi all,I am working on a project where I need to stack two PCBs on top of each other and sharing some signal lines (up to a dozen or so). I need to find a connector solution that is as cheap as possible (cents not dollars), compact (I have little room to work with) and compatible with SMD productionAny ideas?Thanks for your help

author: ataradov
author_rank: Super Contributor
timestamp: September 11, 2016, 03:49:54 am
content: mikeselectricstuffin one of his recent videos showed using SIM card connectors for board-to board interconnect. Have plated pads on one side and SIM card holder on the other. As long as you have reasonable mechanical design, you will be fine.In general, more information is required. For example, what is the distance between the boards?

author: janekm
author_rank: Unknown
timestamp: September 11, 2016, 03:58:42 am
content: Exactly, much more information is required (and probably once you figure that out, it'll become more clear what kind of connector is suitable anyway).What are your requirements for:- mating height (min and max)- board area- do the connectors need to provide mechanical linkage too?- signal integrity- current capability- ease of use- where are you manufacturing (connectors common in one part of the world may not be in another)- most importantly, what is your expected volume (though if that's less than 1000s, you're wasting your time worrying about the cost of connectors...)

author: sirhaggis
author_rank: Regular Contributor
timestamp: September 11, 2016, 04:10:55 am
content: I will check out his video on SIM holder, although not sure it will suit my purposes.- I want the boards as close as possible to each other. Since the mating sides will both be SMD populated the clearance will need to be >1.1mm per side or >2.2mm (call it 3mm), max around 5mm.- The boards are very small with significant size constaints - 25mmx25mm, hence the need to stack them and the need for small connectors.- Mechanical support will be supplied externally with plastic supports- Signals are digital operating up to 10MHz- The connector will need power lines with current requirements <1A- Connectors will be internal so only need to be connected once - i.e. low cycle solution is appropriate- Manufacturing location will likely be in Australia- Volume, if the design works out will be perhaps 2000-4000

author: ataradov
author_rank: Super Contributor
timestamp: September 11, 2016, 04:17:33 am
content: For a really small size - SlimStack from Molex. They are basically purpose-designed for what you need.Molex also makes compression connectors, which are basically the same SIM card holder idea, but a bit smaller.

author: Berni
author_rank: Super Contributor
timestamp: September 12, 2016, 06:22:28 am
content: When i needed to stack PCBs in a tight space i used the Hirose DF40 series of connectors. They take up little PCB space due to there 0.4mm pin pitch, come in lots of different mating heights from 1.5mm to 4mm and they are not too expensive for the large number of pins.If you don't need a large number of pins they might be a bit expensive for you. Also being so tiny they need to be plugged in and out with a bit of care.(I had the firmware department tear them off my prototype boards before)But if you are looking for a reliable and as cheap as possible solution its hard to beat a short pin length 0.1 inch male header simply put between the two boards and soldered on both ends.

author: Smokey
author_rank: Super Contributor
timestamp: September 12, 2016, 06:47:46 am
content: www.samtec.comAll the board to board connectors you will ever need for absolutely anything.Use their configurator. Tell it what you want and it gives you two part numbers. Sweet.

author: daqq
author_rank: Super Contributor
timestamp: September 12, 2016, 07:38:43 am
content: The price is quite a nasty limitation. Looking at farnell and sorting by price (http://sk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&langId=421&storeId=10174&categoryId=700000005019&sort=P_PRICE&eq=N%3D203754%2B2029%26amp%3BNs%3DP_STORE_MARKETING_RANK_FARNELL_SK%257c0%257c%257cP_MAN_PART_NUM%257c0%26amp%3BNtpc%3D1%26amp%3BNtpr%3D1&showResults=true&aa=true&vw=)Gives me these:http://sk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&langId=421&storeId=10174&categoryId=700000005019&sort=P_PRICE&eq=N%3D203754%2B2029%26amp%3BNs%3DP_STORE_MARKETING_RANK_FARNELL_SK%257c0%257c%257cP_MAN_PART_NUM%257c0%26amp%3BNtpc%3D1%26amp%3BNtpr%3D1&showResults=true&aa=true&vw=But if possible I'd avoid them (Multicomp = generic nameless chinese branded under one name)I've tried the SlimStack from molex - relatively cheap and good for what is needed.

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 14, 2016, 01:11:56 pm
content: Quote from: Smokey on September 12, 2016, 06:47:46 amHe is talking about cents, not dollars.Samtec makes great stuff, at a very high price unfortinately

author: Cerebus
author_rank: Super Contributor
timestamp: September 14, 2016, 01:29:59 pm
content: Quote from: DutchGert on September 14, 2016, 01:11:56 pmIt may be that the constraints the OP has had forced on him, or chosen, are going to dictate a somewhat more expensive connector by virtue of the increased mechanical intricacy and accuracy required by that context. That is, the tolerances on 0.1 pin headers are quite loose when compared with the sort of low profile SMT board interconnects that Samtec excel at, and tighter tolerances cost money. But, yeah, Samtec are never cheap.

author: rstofer
author_rank: Super Contributor
timestamp: September 14, 2016, 05:06:30 pm
content: Since you don't need to disassemble the boards, why not use a jumper wire. It doesn't get any cheaper than that and, if necessary, they could be cut and replaced.During development, use longer jumpers (stranded wire?) and for production use cut resistor leads.This was a common construction technique decades back called 'cordwood construction'. Google for 'cordwood construction electronics'

author: Jeroen3
author_rank: Super Contributor
timestamp: September 14, 2016, 05:25:18 pm
content: How about connectors without any plastics at all, fully smd pick-and-place-able?http://www.mtc.de/en/kategorien/smd-contact-springs

author: Cerebus
author_rank: Super Contributor
timestamp: September 14, 2016, 07:16:24 pm
content: Quote from: Jeroen3 on September 14, 2016, 05:25:18 pmThat looks like a really useful collection of parts. I've several times had need of similar and always resorted to fabricating them. Site bookmarked.

author: JS
author_rank: Frequent Contributor
timestamp: September 14, 2016, 11:36:42 pm
content: Why not a PCB in the middle, soldered like those ESP8266 kits. Maybe two identical 1.6mm boards. I don't know the production compatibility of this, but if you need to assemble only once, soldering a few PCBs together should be the cheapest way. I'm thinking all identical thin strips close to the edges of your boards with the pads on one side, you could do this on 2 edges and get more than enough sturdy connections.JS

author: Berni
author_rank: Super Contributor
timestamp: September 15, 2016, 05:24:56 am
content: Quote from: Jeroen3 on September 14, 2016, 05:25:18 pmI used these springs for getting a ground connection to other metal parts in a product. Nicely pick and place friendly and they tend to be designed to spring back even if you smoosh them down to there end of travel where they touch the board.