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Why soldering in SMT called as reflow.

#27598

Why soldering in SMT called as reflow. | 10 March, 2004

Can anyone tell why soldering of paste in reflow machine called as reflow process. Is there any reason or just nomenclature is made.

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#27610

Why soldering in SMT called as reflow. | 10 March, 2004

It's [maybe], because you melt [reflow] the itty, bitty solder pellets [that were formed from a liquid solder] in the solder paste. * Wave solder is melted solder bars [that were formed from a liquid solder], also, but someone named it wave soldering, because of the motion of the liquid solder across the top of the solder pot. * Wire solder is extruded. * Reflow sounds better than remelted.

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Jay

#27613

Why soldering in SMT called as reflow. | 10 March, 2004

You can say "re-flow". It's related with the process.

In order to assemble a PC Board containing lots of components such as PTH (Plated Through Hole) and SMT, usually, PTH type packages and components are soldered first using wave soldering process. And this wave soldering needs the "flow" of liquid soldering (or called wave). After this, SMT components are mounted on the board and heated for soldering. In view of already soldered components, the second soldering can be regarded as another flow. This is why people call it as "re-flow". Actually, flow in reflow does not have any special meaning to rest of packages.

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Primus

#27675

Why soldering in SMT called as reflow. | 19 March, 2004

I'm just getting more involved with SMT, as I've been a through-hole operator for years. But I don't understand how one could reflow SMT components AFTER the through-hole insertion and solder wave are finished. How does one print paste over a board with components in it? We use a stencil printer, what else is there? Besides, isn't it easier to insert through-hole components around the lower-profile SMT components? After all, SMT component placers have a HUGE footprint compared with that of the insertion tooling.

By the way, I've always thought of the term "reflow" to describe the movement of the components inside the oven as they flow across the molten solder on the pads.

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agp

#27687

Why soldering in SMT called as reflow. | 20 March, 2004

I haven't heard of anybody yet who have done smt and reflow after thruhole and solder wave. Thru hole components usually have low resistence to heat and could easily burn when subjected to the 210deg-245deg.C reflow temperature. For pc boards with combined smt and thru hole components,usually smt is done first using printed adhessive on the board before chip mounting but this time the adhessive were placed not on the pcb pad but in between where the body of the components will land. Solder connections of the chip components to the pcb will occur at the wave solder process after thru hole mounting.

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Primus

#27690

Why soldering in SMT called as reflow. | 20 March, 2004

As I said, I'm new, and I've never seen the adhesive dot method. I'm certian our company will stick with paste, though, because we make our own boards (with a vertical plater no less!!!) and contamination is quite an issue. We do a fair amount of rework and paste mounting is much easier to fix. So far there's no need for source-side mounting in our semi-solid-state manufacturing. HA! Source-side-soldering-semi-solid-state sircuits, er, circuits! I slay me.

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pdeuel

#27713

Why soldering in SMT called as reflow. | 22 March, 2004

Looks like most did not help you with your question. REFLOW is to flow and flow again. Flow is when somthing moves. Reflow is when it moves a second time. When solder is applied to the PCB it flows onto the board thru the appatures of the stencle. It then reflows in the oven.

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Primus

#27715

Why soldering in SMT called as reflow. | 23 March, 2004

That one is too obvious. Also shows a twinge of irritation. Somewhat too serious. I like my creative answer better. But in the end does it really matter? I just call it "cooked." We cook boards. 'Nuff said.

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