[TechAssist] Holes gone bad: Soldering a plated via
- From: Wayne Vanaman <Wayne@xxxxxxxxxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Sat, 26 Nov 2005 10:01:02 -0600
A slightly more detailed explanation of holes in the board. Most of
this is taken from memory, it has been a looong time....and I am going
to make up my own definitions, which should be very close to what Pace
USA teaches. I am not trying to write a PCB repair procedure, just an
overview.
DEFINITIONS
Eyelet: A solderable tunnel inserted into a via, longer than the
thickness of the PCB. When the ends are pressed flat onto the PCB they
will tear.
Dual Layer, or Dual sided PCB: A PCB with traces on both sides of the
board.
Eutectic: The lowest temperature at which a mix of two materials will
melt. 63/37 Tin/Lead solder is Eutectic solder.
Fillet: Where the solder forms a curving connection from the trace pad
to the component lead.
Funnelet: A solderable tunnel inserted into a via. Shaped like a
typical funnel with a "spout" on one end. The "spout" part is then
pressed down flat onto the board overlapping and allowing soldering to
the Land.
Land: The part of a Trace including the Eyelet.
Lap: A conductor, usually flat, laid on and soldered to a Trace to
bridge a break.
Multi-Layered PCB: A PCB with traces on both sides of the PCB, and
traces within the PCB substrate material itself.
Pad: the part of a Trace that surrounds the via.
PCB: Printed Circuit Board.
Plastic Range: The temperature spread of a metal alloy between when the
metal is fully melted and fully frozen. Eutectic solder has no plastic
range.
Solder wire: the solder in wire form used for making solder connections.
Substrate: The material the PCB is made of.
Trace: A printed "wire" on the PCB
Via: a hole in a PCB thru which a component lead passes.
Plated Via: a hole in a PCB containing a metal tunnel
The hole in a PCB is called a via.
A via can be a "naked" hole, that is just a hole in the board, or it can
be a "plated via". A plated via is a hole that has metal plating, or a
"tunnel" passing thru the hole.
Work: The component being soldered.
SITUATIONS AND PROCESSES
SINGLE SIDED CIRCUIT BOARD, UNPLATED VIA
On a typical single sided PCB the lead passes thru the unplated via and
is soldered to the trace pad.
SINGLE SIDED CIRCUIT BOARD, PLATED VIA
On some single sided PCBs the vias are plated. The soldered will wick
into the via and form around the pad. If the solder does not wick into
the via there will be air traped, the connection is compromised and will
corrode and fail. Flux is a MUST.
DOUBLE SIDED CIRCUIT BOARD, CONNECTION ON ONE SIDE ONLY
On a double sided circuit board a via may or may not have traces on both
sides of the board. The solder must wickinto the via, as above.
DOUBLE SIDED CIRCUIT BOARD, CONNECTIONS ON BOTH SIDES
While flux is not 100% essential it greatly aids the solderability of
the work. In this case, the solder will flow onto the lead, wick thru
the plated via, and wick up the lead and onto the pad on the other side
of the board. Remember, the time required to complete a solder
connections is NOT LESS than three seconds, and NOT MORE than five seconds.
1. Apply flux. Flux will be on both sides of the PCB, on the lead, and
pad of both sides.
2. Apply a tined soldering iron to the lead on the side of the board
opposite the component.
3. Apply solder wire to the component lead at the solder pencil and as
the solder flows,move the solder wire around the lead to the side
opposite the iron. This creates a uniform temperature thruout the lead
and ensures sufficient heat to fully melt the solder.
4. Maintain heat and solder at the joint.
5. As the component side of the board reaches solder melt temperature
the solder will drop, or wick, thru the via and form a fillet on the
component side of the board, completing the connection.
6. Remove heat and solder wire.
7. Clean and inspect
A POPULAR MYTH
Stay on the solder connection until the air boils out. WRONG! If there
is movement inside the solder connection as the solder passes thru its
plastic state the connection will be plastic, in other words, a cold
solder joint. If a connection is wanting to boil you have one of
several problems:
1. Joint contamination. Clean the connection surfaces. Apply flux and
resolder.
2. Insuffecient heat. The mass is conducting the heat away from the
work before the work is hot, and therefor even though the solder is hot
the work is not, the solder boils but does not melt into the surface of
the work.
Wayne Vanaman
Omega Electronics
6904 W Fairfield Dr
Pensacola, Fl. 32506-3310
Wayne@xxxxxxxxxxxxxxxxxxxxx
WWW.PensacolaTVRepair.Com
850-456-5995 voice
850-458-6369 fax
tjanphyl@xxxxxxxxxxxxxxx wrote:
> Understood now.
> In the case of many-layered boards, these internal layers only have
> connecting traces,not any components in between I assume.It is to
> allow for more wire density without more surface area boards.
> I see. If they needed 400 traces to wire a PCB, it is more compact
> to ,say, have 8 layers with 50 traces= the 400 needed instead of a
> board many times larger.
> Phil
>
>
> Phil Bader, Pres.
> Jan Phyl TV Inc
> Winter Haven, Fl
> (863) 299-8821
> Confounding the wise since 1976
> personal email: pbader@xxxxxxxxxxxxxxx
>
> ----- Original Message -----
> From: becyn <becyn@xxxxxxxxxx>
> Date: Friday, November 25, 2005 7:32 pm
> Subject: [TechAssist] Re: Toshiba TP50F90 color intermittent
>
>
>>Well, then the question is which one of those very tiny holes
>>is
>>the culpret.
>>In the case of a simple old fashioned double-sided, you might be
>>able to
>>snake some
>>wire wrap gauge wire through the hole and solder both sides. That
>>might
>>be OK if there's just a few.
>>
>>However, on a multi- layer pcb there's no definitve way to "know"
>>you've
>>sufficiently flowed the
>>contacts to the inner layers. Besides the holes on these scan
>>converters
>>are about the diameter of a needle and they have a boat load of them.
>>
>>IMHO it's better to just replace the module than to aggravate
>>myself
>>with something that might or might not get fixed after all that
>>effort.
>>Sorry...NO CAR , just an opinion from "Dr. Jim" ! ;-)
>>
>>Jim McVey
>>McVey Alltronix
>>327 Broadway
>>Newburgh N.Y. 12550
>>
>>"If it doesn't play...
>>CALL MCVEY !!!!!!"
>>Factory authorized
>>service for over 20
>>major brands.
>>845 561 8383
>>(Last of the Mohegans)
>>
>>
>>
>>
>>tjanphyl@xxxxxxxxxxxxxxx wrote:
>>
>>
>>>OK. Now: since I am showing my ignorance here I might as well go
>>
>>for
>>
>>>the car, behind door #2!
>>>How exactly does a hole "go bad"? You mean poor solder flow thru
>>
>>them?
>>
>>>Reflow solder is the fix?
>>>Phil
>>>
>>>Phil Bader, Pres.
>>>Jan Phyl TV Inc
>>>Winter Haven, Fl
>>>(863) 299-8821
>>>Confounding the wise since 1976
>>>personal email: pbader@xxxxxxxxxxxxxxx
>>>
>>>----- Original Message -----
>>>From: becyn <becyn@xxxxxxxxxx>
>>>Date: Friday, November 25, 2005 5:16 pm
>>>Subject: [TechAssist] Re: Toshiba TP50F90 color intermittent
>>>
>>>
>>>
>>>
>>>>You know, 'through holes" to make connections on multi-layered
>>
>>and
>>
>>>>double sided boards?
>>>>"Via" is the pcb industry "politically correct" term for the
>>
>>things.>>
>>
>>>>Jim McVey
>>>>McVey Alltronix
>>>>327 Broadway
>>>>Newburgh N.Y. 12550
>>>>
>>>>"If it doesn't play...
>>>>CALL MCVEY !!!!!!"
>>>>Factory authorized
>>>>service for over 20
>>>>major brands.
>>>>845 561 8383
>>>>(Last of the Mohegans)
>>>>
>>>>tjanphyl@xxxxxxxxxxxxxxx wrote:
>>>>
>>>>
>>>>
>>>>
>>>>>have bad via's ????
>>>>>Phil
>>>>>
>>>>>Phil Bader, Pres.
>>>>>Jan Phyl TV Inc
>>>>>Winter Haven, Fl
>>>>>(863) 299-8821
>>>>>Confounding the wise since 1976
>>>>>personal email: pbader@xxxxxxxxxxxxxxx
>>>>>
>>>>>----- Original Message -----
>>>>>From: becyn <becyn@xxxxxxxxxx>
>>>>>Date: Friday, November 25, 2005 1:46 pm
>>>>>Subject: [TechAssist] Re: Toshiba TP50F90 color intermittent
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>Yes, Toshiba's "hyper or scan converter pcb's have been
>>
>>dropping
>>
>>>>>>like
>>>>>>flies lately around here.
>>>>>>Some of them seem to have bad via's which are sensitive to
>>>>>>tapping, or
>>>>>>twisting the can slightly.
>>>>>>
>>>>>>Jim McVey
>>>>>>McVey Alltronix
>>>>>>327 Broadway
>>>>>>Newburgh N.Y. 12550
>>>>>>
>>>>>>"If it doesn't play...
>>>>>>CALL MCVEY !!!!!!"
>>>>>>Factory authorized
>>>>>>service for over 20
>>>>>>major brands.
>>>>>>845 561 8383
>>>>>>(Last of the Mohegans)
>>>>>>
>>>>>>Carol Rundle wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>If your model has standup shielded module( hyper brd.) just
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>behind A/V jack panel, try a little freeze, and heat,
>>
>>inside
>>
>>>>>>module. if it simulates your symtoms, remove brd., ESR
>>
>>lytics
>>
>>>>>>
>>>>>>
>>>>
>>>>,
>>>>
>>>>
>>>>
>>>>>> I've repaired several Toshiba hyper brd's, found
>>>>>>weak,leaky smd lytics, usually find several (8-10)weak,leaky !
>>
>>>>>>Causing symtom's similar to your 's.. hth
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Bill
>>>>>>>Bill'sTV
>>>>>>> Sonora,Calif.
>>>>>>>
>>>>>>>
>>>>>>>Ian Scott <service.depot@xxxxxxxxxxx> wrote:Hello, This set
>>
>>is
>>
>>>>>>>
>>>>>>>
>>>>
>>>>in
>>>>
>>>>
>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>the customer's home and intermittently loses
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>color. When there is no color, the black and white picture
>>
>>has
>>
>>>>>>>
>>>>>>>
>>>>
>>>>a
>>>>
>>>>
>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>noise>in it that appears like you're looking through a screen
>>>>>>door. Both the
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>main picture and PIP will lose color. When I remove the rear
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>cover to
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>work on it, after 10 minutes or so the problem won't occur
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>anymore. I
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>have tried to heat up the pc boards with a hair dryer, but
>>
>>the
>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>symptom>won't return (until I leave). I suspect the comb filter.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>The customer normally watches digital cable and he has had
>>
>>the
>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>cable box
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>replaced. I have asked the customer to try using his DVD to
>>
>>see
>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>if it
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>loses color as well, but so far the results are inconclusive.
>>>>>>>Thanks in advance for any help.
>>>>>>>Ian Scott
>>>>>>>Service Depot
>>>>>>>252 Lasalle Blvd.
>>>>>>>Sudbury, ON
>>>>>>>P3A 1W6
>>>>>>>705-566-3557
>>>>>>>Fax 705-566-3455
>>>>>>>
>>>>>>>
>>>>>>>--------------------------------------------------------------
>>
>>--
>>
>>>>>>>
>>>>>>>
>>>>
>>>>--
>>>>
>>>>
>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>
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>>>>>>>Set Vacation
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>>>>>>>
>>>>>>>Carol Rundle
>>>>>>>brundle@xxxxxxxxxxxxx
>>>>>>>
>>>>>>>
>>>>>>>
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>>
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>>>>>>Version: 7.1.362 / Virus Database: 267.13.7/182 - Release
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>>Date:
>>
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