Breaking the epoxy bond under SMD ?

[Mark Zenier]

....


Belt and braces , to take the mechanical strain off the solder? To scrape
back the epoxy to a clean board , the action of a soldering iron tip on it,
was like the normal reaction of solder-iron heat to epoxy, goes powdery .
Perhaps its bright red as a warning

Red? Sounds like somebody used Loctite Red, (permanent liquid gasket
compund).


Mark Zenier [email protected]
Googleproofaddress(account:mzenier provider:eskimo domain:com)

 

[Uffe Bærentsen]

Den 28-06-2012 16:29, N_Cook skrev:

Transistors , in this case 1-amp-continuous "size" whatever the SO
designation of that is.
If I've not used hot air then a scalpel tip or needle point, as used here,
wedged under , soldering iron melt solder a touch leting the pins relieve
themselves away from the lands , repeat wedging/desolder until fully free.
But this time the epoxy was more structural than just for placement.
I ended up breaking up the transistor body and the epoxy stayed resolute.
Any advice for next time ? if relevant red colour and more than a micro-dot
must have been under it as traces splurged out all around the body.

Have seen thermo curing glue used when SMD and leaded components are
used in a mix on a single sided PCB.
First step in production was to place all glue dots for smd.
Then place all SMD components and cure glue in a reflow oven.
Then place all leaded components and run through the wave solder machine.
In this proces both SMD and leaded components are soldered at the same
time and the glue is to assure that the SMD components do not fall of
during soldering.

BTW the glue was red.

 

[N_Cook]

Den 28-06-2012 16:29, N_Cook skrev:


Have seen thermo curing glue used when SMD and leaded components are
used in a mix on a single sided PCB.
First step in production was to place all glue dots for smd.
Then place all SMD components and cure glue in a reflow oven.
Then place all leaded components and run through the wave solder machine.
In this proces both SMD and leaded components are soldered at the same
time and the glue is to assure that the SMD components do not fall of
during soldering.

BTW the glue was red.

That sounds likely , a mixture of SMD and thru-board componentry on this
pcb. More glue than the dot that would normally be used just for holding SMD
in initial placement.

 

[N_Cook]

Den 28-06-2012 16:29, N_Cook skrev:


Have seen thermo curing glue used when SMD and leaded components are
used in a mix on a single sided PCB.
First step in production was to place all glue dots for smd.
Then place all SMD components and cure glue in a reflow oven.
Then place all leaded components and run through the wave solder machine.
In this proces both SMD and leaded components are soldered at the same
time and the glue is to assure that the SMD components do not fall of
during soldering.

BTW the glue was red.

There was another feature of it I'd noted but dismised ,thinking it was just
due to thin film "dilution" of the colour. The exuding glue blobs around the
SMDs was bright red but the underlying thin material was more beige or peach
in colour - perhaps a side-effect of reflow oven and air exposure while
curing

 

[josephkk]

Thank you. It's just hot & humid in Central FLorida at the
moment. We recently had several days of heavy rain, and a couple
sinkholes in this county from the rain. The problems on the east coast
are north of here. Some areas around Washington DC are without
electricity & running water after recent storms. Luckily, they'll never
run out of hot air.

Yep, that torrent inflicts the whole world. It is a component of the
Santa Ana winds what inflict Lost Angeles from time to time.

?-)