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wave/reflow soldering

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kobik

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wave reflow soldering

Hello,

anyone knows:
1. what the difference between reflow and wave soldering.
2. how i design my PCB placements to wave and to reflow.
3. what are the restrictions.

best regards,
kobi 8)
 

penrico

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wave reflow

Hi kobik:

In wave soldering, the SMT components are patches berfore solded with a special glue. Then PCB cross trought a wave hot of tin, then the tin is paste on the empty metal of components and PCB. This method can used only in one side of PCB, and is not temperature controled method, so is more imprecise than reflow.

The components must be place in same directions attempts to not make "shadows" of tin when you are soldering.

In reflow, first it's make a plate (stencil) with holes in the position of pads to be solder, the you put the stencil over the PCB, and put hot tin over the stencil, then the tin will solde over the pads, after it, you remove the stencil and the PCB has tin on the pads. Now you paste the components on the PCB with a glue, and then put the PCB with components inside a temperature controled furnace, so the tin will solder to components.

There's not special attention in placements for reflow method.
 

kobik

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reflow wave

Hi penrico:

Thx for the fast replay.

i have more questions:
1. what are the benefit of using wave soldering method?
its sound like a non safe way.

penrico wrote:
The components must be place in same directions attempts
to not make "shadows" of tin when you are soldering.

2. can i use a BGA or TQFP components in a wave soldering?

there is a link or PDF that describe the difference between the
two methods and how to design the PCB Layout for this methods.

thx again,
kobi
 

tjalps

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reflow wave soldering

Hello!

I see that this is wery interesting thematics, so I'll try to help a litlle.

Vawe soldering we use mostly for THT components soldering. Since now is trend in use of SMD, we have some compoents wich are still THT( conectors mostly...). For them we use wave soldering ( perhapse selectiv soldering with special frames or selective soldering machines ).

I advise you that you should use reflow soldering for aplying SMT fine pitch components, because otherwise you can have problems with short circuits or missing solder on pads. The manufacturing friendly design is with SMD and THT components on top. Technological procedure is folowing:

1 Apply solder paste with stencil
2 Put SMT components
3 Reflow PCB with components
4 Put THT components
5 Solder them on wave soldering machine

You have finished!! Congratulations. Here is one manual for desining SMT PCB's:

http://www.avx.com/techinfo_documen...fect+Design+Check+List&Category=Surface+Mount

For SMT stencil design you need aditional rules. Check on web.

Do not hesitate to contact me for any aditional info!

Regards!
 

kot_b

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wave and reflow soldering

HI kobik,
u can't use BGA and TFQP with wave soldering
OLNY SO-x
 

gabby

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wave solder reflow

Hi kobik.

I want add some info.

First the wave soldering is the old and first method for soldering,
it popular for the PS side of the pcb(downd side) and the most
use is for thru hole componnet(old chips,cap,connectors).
With the the was added the smt tech for smt passive comp and also
some small ic's that can be solder in that way.
You can't use that method for big ic's (smt, and of corse not bga).

penrico mean on :
The components must be place in same directions attempts
to not make "shadows" of tin when you are soldering.

That is a sigle way to put the comp on the board because the
soldering wave can attack the pads olnly from one way.


The Reflow method is the newest it popular in smt sordering,
If you have smt chips on the top and bottom side you must use
the reflow for the bottom side also , and the connectors solderred
manually or with special mask.

They are a lot of rules how to put the comp for exaple you have a min
distance from a bga and other comp. and also you must know
the ability of your pcb soldering manufatuer technology.

You also must have a best known on make gerber files and also
the solder mask for the comp and the assembly descriptions of the pcb.


Best regards.
 

fematon

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wave soldering after reflow

taking advantage of the discusion I have a silly question... I have seen some boards with SMT devices on both sides of the board, how they do that?, I guess they soder first components in one side, but when they soder the second side how they avoid the already soder components to keep in place?... :?:
 

tjalps

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reflow owen

Hello!

In this case I'd like to sample DC. So you think that this MUX 4051 0r 4067 is quite usable? On what should I be careful?
I now this rule fsamp=2 * fact. But is it realy necessary to put anti aliasing filter on front of ADC if you now that all frequencies will not go over that values. Do you have any good proposal for IC?

Regards!
 

tjalps

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pcb reflow stencil explanation

Sorry for mix.

Hello!

For that you have two options:

1 Double reflow with selectiv soldering

You can first apply solder paste on let say top side of PCB, then you place SMT components and reflow that. You shouldn't put any heavy components on this side( 0805, 1206, so8 .. are OK ). After you do same on the other side. That SMT components are not displaced on PCB you can use two different solder pastes with diferent melting points. For that you also have to adjust temperature profile on reflow owen. After you can solder selective THT components.

For more info
Google: double reflow

2 Reflow on Top + Wave on bottom

As in previous post mentioned you apply paste on top of the board and then also place SMT components. After reflow you turn PCB around and then aplly glue points on the PCB at the places, where components will be placed. After that you should place all components on PCB and reflow that. At this step there is still no solder joint on the bottom. After you can place also all THT components and then drive this board thrue vawe solderin machine. You must be careful that on bottom side you don't have any high components, fine pitch.. After that you only should check the board.

Because I'm not so good in english, I hope that you will understand this. In case of any aditional questions please, do not hesitate.

Best regards!
 

Gemini1706

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tht solder problems

Ok..I know exactly how SMT works..
But NEVER saw or used wave-soldering (sorry guys..new engineer. I guess they do not use it alot these days)..

So, How they do wave-soldering?
I did not get it from what is wrote above...

Anybody to explain?

Thanks in advance..
 

tjalps

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wave soldering reflow selective different

Vawe soldering is completed with folowing phases:

1. Flux zone
First you must apply flux on the soldering surface.

2. Air knife
With this you remove waste of flux, so that you get only wery thin surface of flux on the soldering side of PCB.

3. Preheating
With this zone you are prepearing PCB for soldering in bath. That there is no thermal stres of PCB( broken components or tracks ). You also dry the flux on the bottom side.

4. Soldering
In one specila Titanium bath you have heathers and solder heated over melting point. You also have one pump with regulated electrical notor. With speed of this motor you adjust the height of soldering vawe. Usualy xou have two independent vawes:
a Chip wave
It's more used for SMT components soldering in combination with main wave. The direction of solder movement is same as moving of PCB.
b. Main Wave
Main can work alone or with Chip wave as I mentioned before. The direction of solder flow is oposite to direction of movement of PCB.
Now wery important factor in bath is temperature and height of wave.

Then is only cooling on the exit of machine.
Also important parameter is speed of transport conveyer system.


Please, do not hesitate to contact me for any aditional info!

Regards!
 

Gemini1706

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wave vs. reflow soldering

Thanks much for the explanation.

So they actually "spray" the melted solder using the bump into the PCB? i.e. the melted solder is contained in a sepearte container?
In this case, how they garantee that the solder will not spill under some components? Just guarantee of solder rsist?
I beleive that solder shorts..etc. will be a problem..


Or, the solder is tinned into the PCB, kinda like the SMT, then a wave of heat is applied?

Thanks in advance..
 

tjalps

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reflow wafe

Well here you have two diferent things. First is flux( alcohol based or water based ). You can apply that with spray or foam fluxer unit. This is placed at the begining of machine. This can be sprayed and not solder.

Solder is placed in special bath sorunded with powerfull heaters. You can put inside over 200kg of solder bars. They are later melted on temperature around 240 degeres celsius. This one you basicly apply on joints( pads and component pins) with driwing bottom of pcb over this bath. Each part of PCB should me there for cca. 3 secunds.

Regards!
 

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