This is continue of part one. Following advises are for how to solder SMD parts with improved technology.

Oven isolation

As isolation material there can glass insulation be used. In this case glass insulation was packed in aluminum foil:

Inspected improvement in heating speed:

• 0.95% without isolation;

• 1.50% with isolation only inside oven;

• 1.72% full isolation.

Preparing the mask for applying solder

Using the mask for applying solder paster may improve solder quality and board may look more professional.

As mask material is plastic plate of 0.2mm used. Mask also can be etched as usual circuit board.

If circuit design is made by using Eagle CAD software, then for making mask go to Tools->DRC->Masks. In the field CREAM choose minimum 0, maximum10mil. In the field % valuescan be corrected.

In order to expose negative of SMD plates in Eagle select layer tCream:

• File->CAM Processor;

• Select layer Dimensions and tCream;

• Select in Devices option PS_INVERTED;

• make sure that Scale is equal to 1;

• File: name.ps

• Process Job;

• File name.ps should be placed in working directory of project;

• Set GSView or other environment for reading .ps files;

• Open name.ps file and print it.

It is most convenient to etch the mask plate as usual circuit board. For this special brass plate may be used which has both sides covered with photo-resistive coating. Peal one protective film other leave asit is. This way you can etch through hole not the all plate.

Next stage is putting cream on

First of all fix the mask to the board so that mask areas matches SMD solder areas:

apply cream smoothly by using a strip:

Hold the strip at the angle of 45 degrees so the paste distributes evenly:

Take the mask off the circuit boar. Try to remove it vertically so that solder nicely stays on the board.

Then put SMD components on the mask by slightly pressing them down. Make sure SMD parts are well centered.

Put board in to the oven as discussed earlier. And you should get nice circuit board:

Soldered SMD board looks more beautiful and smooth

Few problems may occur while soldering with soldering paste in oven. One of them short circuit beween SMD legs. Dont panic, just apply enough flux and use solder remover. Next time make mask holes smaller when designingin Eagle.

Sometimes solder paste may dry out without soldering parts. This means that oven heats too slowly. One os solutions may be to shorten drying time.

Sources: www.radiokot.ru, http://cxem.net, http://wiki.jelectronique.com.

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This entry was posted on Wednesday, May 23rd, 2007 at 2:36 pm and is filed under Electronics Tutorial. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.