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TM
11-5820-919-40-1
chips, and gouges are not
3.
Cracks,
The  repair  of  circuit  cards
3-18.
acceptable  on
the  contact  strip  edge  of
requires  proper  tools  and  careful  work
the  board.
habits.  Excessive  heat  when  soldering,
or  undue  force  applied  to  components  or
4.
Cracks  or  chips  should  not  extend
to  the  circuit  card,  can  seriously  dam-
from
one  conductor  to  another  conductor.
In  general,  the  fol-
age  the  assembly.
lowing  precautions  should  be  observed:
Delamination  of
the
base
material
5.
is  not  acceptable.
Never try to save a component part
1.
CIRCUIT  CARD  ETCH  STANDARDS.
at  the  possible  expense  of  damaging  a
Circuit  card  etch  standards  are  as
circuit  card.  Most  component  parts  can
follows :
be  clipped  from  the  circuit  card.  When
clipping  the  defective  part,  be  careful
Cracks, pits, or voids in the
1.
to  protect  the  printed  circuit  conductor
contact  strip  area  are  not  acceptable.
(etch)  and  other  component  parts.
2.
Scratches  which
expose
the
copper
are  not  acceptable.
3.
Cracks , pits, or voids in any etch
A  vacuum  resoldering  unit  should
2.
which  reduce  the  conductor  by  more  than
be used, if available, to remove the
20  percent  are  not  acceptable.  No
leads  of  a  clipped  part.  The  technical
defect  should  reduce  the  conductor  to
manual  for  the  vacuum  resoldering  unit
less than 0.010 inch.
contains  operating  procedures  for  the
Basically,  the  vacuum  resoldering
unit.
4.
Lifting  of  a  conductor  above  the
a high flow
unit  operates  as  follows:
surface of the board is not acceptable.
hole, across the pads and around the
5.
Reduction in the area of any pad
leads to remove the solder and cool down
in excess of 25 percent is not accept-
these  areas  to  prevent  resweating  of  the
able.  Cracks,  pits,  or  voids  should  not
lead.  At  the  same  time,  the  temperature-
extend  to  a  plated-through  hole.
controlled  resoldering  tip,  which  ini-
tially provided the heat to melt the
STORAGE  AND  HANDLING  OF  CIRCUIT
solder,  is  cooled  rapidly  by  the  air
CARDS .  When  stored,  circuit  cards
flow  to  prevent  further  heat  from  being
Once the air
should  be  wrapped  individually  in  poly-
applied  to  the  workpiece.
flow  is  stopped, the tip heats up rap-
ethylene  bags,  or  equivalent,  and
Other  objects
idly  for  continued  vacuum  resoldering.
stacked  in  storage  pans.
The  coaxial,  in-line  design  of  the  hand-
should not be placed in the storage pans
with  circuit  cards.  Avoid  touching  the
piece  allows  molten  solder  and  clipped
leads  to  be  drawn  into  the  heat-resistant
circuit  card  surface  with  bare  hands  or
fingers.  Handle  the  circuit  card  by  its
chamber  where  solder  is  solidified.
edges.
Exercise  care  when  using  a  sol-
CIRCUIT
CARD
REPAIR
PROCEDURES.
3.
dering iron to remove the leads of a
clipped  part,  to connect a new part, or
WARNING
to  service  the  circuit  card  itself.
Vapors  emitted  during  certain
Circuit  cards  are  easily  damaged  by
Prolonged  application  of  heat
circuit  card  repair  procedures
heat.
may  be  irritating  to  personnel.
will  destroy  the  adhesive  quality  of  the
Always  perform  circuit  card
bonding  agent  that  holds  the  printed
procedures in a well
repair
etch  to  the  circuit  card.  Use  the  recom-
ventilated
area.
mended  soldering  iron,  or  equivalent.


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