Wave soldering smt components

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Hello Everyone! I have encountered a situation where I hav... - Dec 14, 1999 by

Sure KA, it's done every day. Be sure that the components ... - Dec 14, 1999 by John Thorup

Hello KA, When producing in kind of PCB product you have to... - Dec 15, 1999 by TNT

Hello Guys; I "ll like to add some comment on Mr John mess... - Dec 17, 1999 by cklau

KA, Joshua makes a good point. A wave solder fixture will... - Dec 17, 1999 by

#8187

Wave soldering smt components | 14 December, 1999

Hello Everyone!

I have encountered a situation where I have surface mount components on the backside of the board and I need to wave all the through hole leads on the backside as well. Can this be done? I thought of the possibility of adhering the backside surface mount components in place with epoxy and then running the board through the wave. Am I on the right track?

I would appreciate any comments or suggestions.

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John Thorup

#8188

Re: Wave soldering smt components | 14 December, 1999

Sure KA, it's done every day. Be sure that the components to be used on the bottom can take the maximum heat of the wave and the delta T of entering the wave. Depending how complex the bottom side is you will get better results with attention paid to Design For Manufacture and an appropriate wave machine. Select the correct adhesive for your board and method of application. Loctite is just one supplier. Search this forum's archives for more info and good luck. John Thorup

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TNT

#8189

Re: Wave soldering smt components | 15 December, 1999

Hello KA, When producing in kind of PCB product you have to base much of your decision on cost effectiveness, time, and quality. In order to get the best of all three you have to decide which you want to be your top priority. By adding an epoxy to these parts, you can risk coplanarity issues with the surface mount pads. The time its takes to add this epoxy by machine or by hand can also be burden to your budget. If you want to run these boards through the wave but don't want to waste time on the epoxy you should look into a fixture that shields the components from excessive heat and solder but remains open for the through-hole leads. If you do choose to go with the epoxy invest in a product with minimal heat expansion. You will also need to decide on your torque specifications. Look to have the glue cured in you SMT reflow ovens. The parts can then be examined for compliance before they reach the wave solder.

I hope this helps... Have a good one.

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cklau

#8190

Re: Wave soldering smt components | 17 December, 1999

Hello Guys;

I "ll like to add some comment on Mr John message , see below..

"Be sure that the components to be used on the bottom can take the maximum heat of the wave and the delta T of entering the wave."-John

The required preheat temp , that is delta T depends on the type of flux used during flow soldering.For example the more common low residue fluxes require a preheat temp of 120 degrees (Temp taken from the wave solder side of the PCB's).

Basiclly solder flux can be categorized in to 3 main groups:

1) Non-activated flux (e.g rosin-based fluxes) 2) Mildly activated flux(e.g rosin-based or synthethic fluxes) 3) Highly activated flux(i.e water soluble fluxes)

The choice for a particular flux type depends mainly on the products to be soldered.So choose it wisely. BTW it is quite uncommon for a PWB to be flow solder to be design in such a way (leaded component on both side of the board).All my process engineer will be shock!, if I were to design something like this.

Till then good luck and happy holiday.

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Marty Wetzel

#8191

Re: Wave soldering smt components | 17 December, 1999

KA,

Joshua makes a good point. A wave solder fixture will allow you to process your double-sided boards without having to add the epoxy step. The one time fixed cost of a fixture is quickly offset by the time that you save by not gluing your SMT. A selective solder pallet lets you solder only the through-hole components while protecting all of your solder side SMT. There are plenty of fixture houses out there but I recommend: 1) EMC Global Technologies 2) GSC (Garland) 3) Stone Mountain

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