spring clip / low profile fastening method for electronics boards

[kelroy]

I'm looking for a low profile way to fasten a nominally square electronics board to a mating hunk of metal. The smaller the better. It also has to be a positive pressure feature, since the system will be in a high shock and vib environment. I'd like to keep it to COTS stuff if possible. Spring clips or other clever ways of capturing the board are preferred, since I don't have room to put screws in the four corners...

 

[drawoh]

Kelroy,

The inherent nature of spring clips is that they are low force. This is not a good characteristic for a high shock environment.

Could you use an external screw clamp?

JHG

 

[kelroy]

well, that's my baseline -- metal standoffs and M3 screws....but screws are big and take up board space. My boards are only <5 centimeters across. Card guides are deireable in low vib envoronments (transportation, etc.), since they're low space/low cost, but can turn the assembly into a baby-rattle in high shock high cycle environments. I was hoping a hardened Be spring would provide enough force, but don't have the time/money to toy with different designs....was looking for something else people were using.

 

[israelkk]

It is always amase me that there is no time to invest in agood design but, there is always all the tiime in the world to fix bad designs.

 

[sreid]

3M VHB Foam Tapes stick things together with incredable strength. Insulating and some vibration damping.

http://solutions.3m.com/wps/portal/...Mz0vM0Q9KzYsPDdaP0I8yizeId3Qz0C_IcFQEAJBx3Xk!

Small quantities sold at McMaster-Carr.

 

[drawoh]

Kelroy,

I was thinking more along the lines of a strap clamp with an external screw.

Does the board have to be that small?

How about glueing or soldering the board in place? Soldering will give you an excellent ground connection.

JHG

 

[thermcool]

Soldering seems to be good method in this case.

 

[kelroy]

Soldering is out because of the need for re-workability (especially in the prototype phase when boards will be being checked, swapped, repaired, and tweaked).

 

[drawoh]

Kelroy,

I have done very little soldering to PCBs so I am not the expert on this, and I am prepared to be corrected by the people who have done this.

There are desoldering tools out there. Technicians can remove components from PCBs without making a mess, as far as I can tell. Perhaps you should chat with your manufacturing people.

JHG

 

[IRstuff]

The issue is not whether you can rework a board ONCE, but whether you can do that repeatedly. EVERY time you apply heat to a circuit trace, you degrade its ultimate life.

TTFN

 

[Tunalover]

Wedgelocks work quite well in shock and vibration. They also provide good thermal benefits if the boards are designed to work with them.


Tunalover

 

[kelroy]

tunalover (nice call-sign btw), I think I know what your talking about, but can you elaborate? We considered some "V-clamp" configurations, but hadn't seen them used successfully and were worried about stress concentrations at the points of contact.

Thanks