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TSSOP and wave soldering

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andyyau

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Hello,

I am going to use a TSSOP-8 IC. The PCB must be used with wave soldering process. The problem is that the pitch of the TSSOP ic is so small and should be 0.65mm. After waver soldering, I think more pins will be shorted together with solder.

Is there any method or any special footprint to make the solder pad better for this problem?

Hope someone can help!
 

kot_b

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Try to make first and last pads on each side almost 3 times bigest, than other pads. May be it helps. This method use for soldering SO packages with wave.
 

andyyau

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Hello, mr_ghz

I had read this file already. But the problem is that at page 2 of it, it states that "Not suitalbe for wave soldering" for TSSOP8!!

This is the problem. Any other help?

Andy
 

BigBoss

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A silkscreen lines ( white color thin lines ) between leads may help you. Namely , drawing very thin silkscreen layer ( component side) lines will prevent shorts I guess..

Rgrds
 

jodokus

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Check moisure sensitivity for your tssop.
The manufacturer can tell you this.
If the component is moisture sensitive it is not suitable for wave soldering at all! This is the case for many plastic smd devices.
Both JEDEC and IPC have literature on this subject.
 

Hero

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Hi,

TSSOP and fine pitch componenets are not suitable for the wave soldering.
If you use wave soldering you will have too many production faults and it will be very expencive to repair every shorted board.

Also you will have problems with IC overheating during wave soldering so in some cases you can expect IC fault caused with overheating.

My recomendation is to mount TSSOP IC on the oposite side of components witch will be wave soldered and use reflow method for TSSOP.

Wave soldering is not suitable for all semiconductor devices and may be used for passive components, PTH connectors and other devices resistant to long heating.

Regards
 

sokala

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I currently solder chips with over 200 pins and very small pitch.The secret is using of right ammount of flux and a tip with concave depression(miniwave).A single pass over the whole line of pins at proper temperature will let them perfect soldered.I recommend you using HAKKO tips as VK50 or VK51 if you use a hakko station.A little bit exercise before will help you enormous.
Good luck
 

flatulent

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metcal web site

The Metcal soldering iron company has many application notes at their site. One is about how to use their special tip to solder these parts. Their tip is similar to the one discussed in the previous post.
 

bbohica

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I agree with HERO. You should paste, place, and reflow the component. Of you must use a single sided board, create a mask for your TSOP and other fine pitched parts and then send it through the wave.
 

Frosty

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If you are preparing such a mixed technology board for wave soldering you should do this.

Never try to wave solder a fine pitch part, if you must make sure it can be suitable for wave solder in first place, see posts above.

Make all fine pitch parts on bottom (solder lead side) reflowed first, then reflow top side second.

If you have large parts, 0805, o603 and you really want to wave solder them , you can glue and place them now.

Before flow (wave) soldering you should make a wave solder pallet or carrier which has been made for this board, the pallet should only have apertures around the leaded parts you wish to solder and mask off the other areas like your TSOP. Most likely you will have to landscape or contour the surface of the pallet so that there are pockets machined out for the bottom side parts like your TSOP to sit into, that way the board will mount flat on the pallet.

To do this your wave solder machine will need to have a pressure wave (2 preffer) as well as a bath as the underside pockets in the pallet will be deep because of the masking of the other parts. If you have gas expansion issues in small pockets you migh need to make a small cut out from the pocket to the outside edge but then you should just use the pressure wave & skip the bath phase.
 

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