[wxsig] hot glue follow-up

[Gerald Creager]

Point taken. And different experiences. With the DC products and the 
right solvent (acetone and mineral spirits) removal doesn't have to be 
too hard. Without the right solvent, it's a pain!

gerry

John Bennett wrote:
> The reader should understand that while there may be some heat stress 
> associated with applying hot glue, it does not approach the heat stress 
> that components and boards are subjected to when traveling through a 
> solder wave machine or just simply using a soldering iron.
> 
> As to physical damage, in the Heath ID5001 weather station assembly of 
> the humidity sensor, they used a conformal coating similar to the 
> Dow-Corning products mentioned. The humidity sensor on that station had 
> a life span of about 3-4 months at best. I routinely had to replaced 
> those sensors (actually still have a handful left). Removing that 
> conformal coating the first time was tedious and far more difficult than 
> the hot-glue. The potential for damage was there as well.
> 
> What I'm trying to say is that you should not be afraid to use hot glue 
> for fear of damaging anything. I feel the low risk involved far 
> outweighs the advantages. That and hot-glue does not give off toxic 
> fumes when applied as some conformal coatings do.
> 
> Gerald Creager wrote:
>> There are several spray-on and paint-on conformal coatings (eg., 
>> Dow-Corning 3140, 3145) that are less likely to thermally stress 
>> components or traces, or provide a mechanical damage potential upon 
>> removal, than hot glue. That said, this is certainly a testimony to 
>> adequately protecting exposed PCB traces and should be taken to heart!
>>
>> gerry
>>
>> John Bennett wrote:
>>> About three years ago I installed a T-238 station with the X1W-1, 
>>> X1W-2 and X1W-4 kits. The rain gauge option had been installed on the 
>>> X1W-2 (outdoor temp/humidity). It has been intermittent for some time 
>>> and finally stopped working.
>>>
>>> I had wrongly assumed that the counter chip had been fried. After 
>>> determining the DS2423 was OK, I checked the opto-isolator to find 
>>> that Vcc was missing on pin one. It did not take long to find the 
>>> problem. Part of a trace had corroded away. The part that had 
>>> vanished was not covered with hot glue. The only protection was the 
>>> solder mask on the PC board itself. Moral of the story here is that 
>>> all traces pads, pins, etc. that are exposed must be somehow sealed. 
>>> Just be certain to follow the guidelines I gave on applying the glue 
>>> in the manual.
>>>
>>> As a point of interest, only the bottom of the board had corrosion 
>>> problems. The board was installed in a Davis radiation shield and 
>>> therefore was facing down. Apparently moisture with some contaminants 
>>> routinely collects on bottom of the board which is facing up. The top 
>>> of the board which faces down showed virtually no signs of corrosion.
>>>
>>> In the process of trouble-shooting, it was necessary to peel away 
>>> some of the hot glue. This was not an easy task, but when I did get 
>>> if off, ICs, board, traces - virtually all components looked as if 
>>> they had just been installed. No mold, dirt, peeled off paint or 
>>> solder mask. Hot glue works. It just doesn't look pretty.
>>>
>>> 73,
>>> John Bennett, N4XI
>>>
>>>
>>> _______________________________________________
>>> wxsig mailing list
>>> wxsig at tapr.org
>>> https://www.tapr.org/cgi-bin/mailman/listinfo/wxsig
>>

-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843