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SMD: solder or solder paste ??

2014-08-06 by qz9090@...

When soldeing SMD components it seems that one of two approaches can be used.

Note: I'm new to SMD so I may be totally off-base on this one.

It seems to me that some of you prefer to use solder paste and some of you use very small diameter, rosin filled solder. What are the pros and cons of each? Is one approach better than the other? If using solder, what diameter should one use?

Thanks.

FP

Re: [Homebrew_PCBs] SMD: solder or solder paste ??

2014-08-06 by James

Solder paste is usually used only when doing reflow (reflow oven, toaster oven, frying pan, hot air...)

You can use it with a soldering iron (by placing the paste, placing the component, and touching with iron), but there's no real advantage.

A 0.4mm - 0.6mm diameter solder is just fine if you are doing SMD with a soldering iron. My general process is to add solder to one pad, place the component with tweezers while keeping the solder molten with the iron and using the iron tip as a "stop" to help align the part, remove the iron and let the solder harden, then go do the other pad(s). You can do this a lot faster than with through hole, a lot faster. Extra flux is advisable when doing IC's, helps prevent bridges.

On Wed, Aug 6, 2014 at 2:27 PM, qz9090@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

When soldeing SMD components it seems that one of two approaches can be used.

Note: I'm new to SMD so I may be totally off-base on this one.

It seems to me that some of you prefer to use solder paste and some of you use very small diameter, rosin filled solder. What are the pros and cons of each? Is one approach better than the other? If using solder, what diameter should one use?

Thanks.

FP

Re: SMD: solder or solder paste ??

2014-08-08 by qz9090@...

James,
When using a hot air rework station, I would solder paste, right?

Can a rework station be hot enough to use with regular solder (for attaching components or removing components)?

Thanks.

Re: [Homebrew_PCBs] Re: SMD: solder or solder paste ??

2014-08-08 by Stefan Trethan

A hot air station will melt wire solder.
(The solder alloy is the same, or rather the same alloys are available, solder paste is just tiny balls mixed with flux).

However using wire with a hot air station is awkward, as the hot air will melt the wire before you reach the joint.
Typically you would use hot air as a rework tool, to swap parts without adding any fresh solder.
(Left hand holds the hot air, right hand holds the tweezers, for right handed people, thus the hot air station is positioned left on the bench unlike the soldering iron).
You might often touch up with a regular iron and wire solder after the rework, if the solder quantity or quality is not sufficient.

You can also use a hot air rework tool to reflow solder paste, I do that often for small boards.
However as with all paste work the temperature rise timing is important, you need to apply the hot air gently or you will get stray solder balls and stuff.

ST

On Fri, Aug 8, 2014 at 5:26 PM, qz9090@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

James,
When using a hot air rework station, I would solder paste, right?

Can a rework station be hot enough to use with regular solder (for attaching components or removing components)?

Thanks.

Re: [Homebrew_PCBs] Re: SMD: solder or solder paste ??

2014-08-09 by James

On Sat, Aug 9, 2014 at 3:26 AM, qz9090@... [Homebrew_PCBs]
<Homebrew_PCBs@yahoogroups.com> wrote:

> When using a hot air rework station, I would solder paste, right?

Yes

> Can a rework station be hot enough to use with regular solder (for attaching components or removing components)?

For removing, sure, for attaching, errm, it would melt it, solder, but
it would be a pretty tedious way to do it.