E Mac,

I assume that what you mean by what you said below is that you have a keypad that is
mounted on a PCB that additionally has seperate IC's which are either BGA's or
TSOP's, as opposed to a keypad that itself is either in a BGA or TSOP package.

That being said, a keypad of any type should always be firmly mechanically
supported, prefferably directly to the chassis of the device that it is mounted in.
Period.

A PCB should never be allowed to "flex" under this or any other type of directly
applied mechanical pressure, since such "flexing" can indeed cause problems with
solder joints.

Please note that some very small PCB's, such those in a cell phone, may seem to
violate the above statement, but if you look at the amount of pressure, verses the
size of the PCB, and specifically the thicknss of the PCB along with the mechanical
support for the PCB, I think that you will find that they have indeed provided good
mechanical support, and do not allow the PCB to flex under the pressure applied to
the keyboard (keypad).

j


----- Original Message -----
From: "E Mac" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, July 19, 2005 10:47 PM
Subject: [DC] Stress on solder joints on fine pitch components caused by keypad
action


> Investigating a PCB design which implements a keypad design with fine pitch BGAs
and TSOP ICs. My concern is possible  stress and vibrations induced by the keypad
operation could transfer stress to the solder joints of the fine pitch IC causing
the weakening of their solder joints.
>
> Does anyone have experience how to model the stresses on solder joints?
>
>
>
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