I want to join two PCB boards with "Headers" type connectors, like this image:
But the separation between both PCBs must be 4.8mm, as shown in this other image.
But with the connectors mentioned, they are very long and I cannot find a separation, nor close to the desired value.
I have seen some special connectors (SMD/SMT), but I can't find them.
Any suggestion or comment is welcome.
The shroudless strips you plan to use are fragile and tend to rip SMD pads off the PCB. I strongly recommend you use mezzanine board-to-board connectors instead.
My Identiconn utility lets you select the mating height of mezzanine connectors. For 4.8 mm mating height, it lists 17 parts.
Of those, I would recommend the Amphenol Conan MezzSelect because it's small and it is compliant with variations in the board spacing, giving you more flexibility.
{Source: Digikey}
Using standard header pins/sockets mounted on their side, you can get this down to <3mm.
Headers do two things: provide an array of electrical connections, and mechanical alignment. Depending on how many pins, and how many are arranged on the board(s) and where, rotational alignment may be weaker, but location is always dictated by the pin and socket.
Strength is determined by header type and mounting; SMT headers like shown, you don't want much stress on, as the solder joints, or pads themselves (foil-laminate bond), aren't especially strong. SMT connectors are best for low stress, low cycling connectors (e.g. internal, user-inaccessible), and providing vibration damping and strain relief is recommended.
You might consider separating these functions, by using a spring or pogo-pin header, and separate mechanical alignment. The electrical contacts can then be simplified, perhaps permitting a lower profile.
Headers without alignment include spring contact arrays like TE Connectivity AMP Connectors 2199055-2, KYOCERA AVX 009188006020062, or battery connectors like KYOCERA AVX 009155005002016; pogo headers like Preci-Dip 811 (or Mill-Max), and targets like Preci-Dip 800, Mill-Max 319, etc., or plain PCB pads (preferably hard gold plating; ENIG has very little cycle life, let alone against vibration).
There are also single pogo pins and targets such as here: Contacts, Spring Loaded (Pogo Pins), and Pressure | DigiKey; effectively, you might craft your own bespoke connector by arranging pins in ideal locations, rather than having to collect them into headers.
Locating pins and mounting screws/standoffs transmit between-PCB stress and vibration, addressing one of the drawbacks of using headers alone. (See also: board edge guides to maintain orientation, especially for right-angle mounting with headers, edge connectors, in card cages, etc.)
Alignment pins can be a part of the enclosure, sliding or press fit into a PCB (any standard mechanical parts apply: hard pins, roll pins, etc.), or press-in or swaged hardware. For the latter, see PEM locating pins for example. You may find press-in or solder nuts, studs, standoffs, etc. useful for various mechanical assemblies. Examples: Keystone 24939, Würth Elektronik 9774030360R, PEM SMT types, etc.
Are you set on connectors? You could use pogo-pins on one board and plain copper pads on the other, and bolt the boards together so that all pins make contact with the pads. The pogo pins are spring loaded.
Aside from that, first thing I thought was "does he need it to be disassemble-able?" because the simplest would simply be to use a regular header and solder it on the other board (for 2.54mm spacing) or use a custom spacer when bolting the boards down (for higher, up to the contact length and some). But I'm sure you already thought about it long ago, so it's more like a note.
