Philips BDL4785SL/00, Руководство по обслуживанию

Страница: 133 / 141

BDL4 7 85 S L LCD 133
5HSDLU7LSV
0. W a rnin g
All ICs a nd ma ny other se m i -conductors a re susceptible to
electrost a tic disch a r g es (E S D). C a reless h a ndlin g durin g rep a ir c a n
reduce li f e dr a stic a lly . When rep a irin g , ma ke sure th a t you a re
connected with the s am e potenti a l a s the ma ss o f the unit vi a a wrist
wr a p with resist a nce. Keep co m ponents a nd tools a lso a t the s am e
potenti a l!
1. S ervicin g o f S MDs ( S ur fa ce Mounted Devices)
1.1 Gener a l c a utions on h a ndlin g a nd stor ag e
- Oxid a tion on the ter m in a ls o f S MDs results in poor solderin g .
Do not h a ndle S MDs with b a re h a nds.
- Avoid usin g stor ag e pl a ces th a t a re sensitive to oxid a tion such a s
pl a ces with sulphur or chlorine ga s, direct sunli g ht, hi g h te m per a tures
or a hi g h de g ree o f hu m idity. The c a p a cit a nce or resist a nce v a lue o f
the S MDs ma y be aff ected by this.
- Rou g h h a ndlin g o f circuit bo a rds cont a inin g S MDs ma y c a use
d amag e to the co m ponents a s well a s the circuit bo a rds. Circuit bo a rds
cont a inin g S MDs should never be bent or f lexed. Di ff erent circuit bo a rd
ma teri a ls exp a nd a nd contr a ct a t di ff erent r a tes when he a ted or cooled
a nd the co m ponents a nd/or solder connections ma y be d amag ed due
to the stress. Never rub or scr a pe chip co m ponents a s this ma y c a use
the v a lue o f the co m ponent to ch a n g e.
S i m il a rly, do not slide the circuit bo a rd a cross a ny sur fa ce.
1. 2 Re m ov a l o f S MDs
- He a t the solde r ( f or 2 -3 seconds) a t e a ch ter m in a l o f the chip. By
m e a ns o f litz wire a nd a sli g ht horizont a l f orce, s ma ll co m ponents c a n
be re m oved with the solderin g iron.
They c a n a lso be re m oved with a solder sucker (see Fi g . 1A)
While holdin g the S MD with a p a ir o f tweezers, t a ke it o ff g ently usin g
the solderin g iron's he a t a pplied to e a ch ter m in a l (see Fi g . 1 B).
- Re m ove the excess solder on the solder l a nds by m e a ns o f litz wire or
a solder sucker (see Fi g . 1C).
While holdin g the S MD with a p a ir o f tweezers, t a ke it o ff g ently usin g
the solderin g iron's he a t a pplied to e a ch ter m in a l (see Fi g . 1 B).
- Re m ove the excess solder on the solder l a nds by m e a ns o f litz wire or
a solder sucker (see Fi g . 1C).
1.3 C a ution on re m ov a l
- When h a ndlin g the solderin g .iron. use suit a ble pressur e a nd be
c a re f ul.
- When re m ovin g the chip, do not use undue f orce with the p a ir o f
tweezers.
- The solderin
g iron to be used ( a pprox. 30 W) should pre f er a bly be
equipped with a ther ma l control (solderin g te m per a ture: 22 5 to 2 50 C).
7KHFKLSRQFHUHPRYHGPXVWQHYHUEHUHXVHG
1.4 Att a ch m ent o f S MDs
- Loc a te the S MD on the solder l a nds by m e a ns o f tweezers a nd solder
the co m ponent on one side. Ensure th a t the co m ponent is positioned
correctly on the solder l a nds (see Fi g . 2 A).
- Next co m plete the solderin g o f the ter m in a ls o f the co m ponent (see
Fiq. 2 B).
2 . C a ution when a tt a chin g S MDs
- When solderin g the S MD ter m in a ls, do not touch the m directly with
the solderin g iron. The solderin g should be done a s quickly a s possible,
c a re m ust be t a ken to a void d amag e to the ter m in a ls o f the S MDs
the m selves.
- Keep the S MD's body in cont a ct with the printed bo a rd when
solderin g .
- The solderin g iron to be used ( a pprox. 30 W ) should pre f er a bly be
equipped with a ther ma l control (solderin g te m per a ture: 22 5 to 2 50 C).
- S olderin g should not be done outside the solder l a nd.
- S olderin g f lux (o f rosin) ma y be used, but should not be a cidic.
- A f ter solderin g , let the S MD cool down g r a du a lly a t roo m te m per a ture.
- The qu a ntity o f solder m ust be proportion a l to the size o f the solder
l a nd. I f the qu a ntity is too g re a t, the S MD m i g ht cr a ck or the solder
l a nds m i g ht be torn loose f ro m the printed bo a rd (see Fi g . 3).