Tips to reduce engineering questions for your SMT stencil orders

Common situations which cause stencil enigneering questions, and a few tips to reduce them and shorten the time of the whole process.

1. Design a solder paste layer in your Gerber File

It is highly recommended that you design a solder paste layer in your gerber file, and include all needed apertures in the solder paste layer.

If you are certain that the solder paste layer is already processed and ready for production, please remark in advance like 'Please make the stencil as per the solder paste layer, and don't modify the file.' So our engineers will proceed with the solder paste layer directly. (As shown below)

2.Match solder paste layer with solder mask layer

Try to keep consistent of the solder paste layer and solder mask layer, in terms of pad quantity, sizes, and shapes. Please remark in advance how to process the difference if any exists.(As shown below)

3.Update your design and select the correct specifications

Last but not least, please try to update your design and select corresponding specifications correctly, like the 'Fiducials' in the new orders and avoid repetitive engineering questions.

Typical engineering questions and how to avoid them

You may check the following typical situations causing engineering questions, and try to avoid them.

1. There are items on solder mask layer, but not on solder paste layer.

Example：

Tips:

1. If the marked items don't need to open on the stencil, you can remark when ordering. For example, 'Please make the stencil according to the solder paste layer, and ignore the difference on solder mask layer.'

2.If the marked items need to open, please add them on the solder paste layer accordingly to avoid engineering questions.

2. There are different sizes or shapes between solder paste layer, copper layer, and solder mask layer of the same items.

Example：

Tips:

Please try to keep the solder paste layer consistent with solder mask layer and the copper layer. If you want us to follow the solder paste layer and ignore the difference, please remark when ordering. For example, 'Please make the stencil according to the solder paste layer, and ignore the difference on solder mask layer.'

3.There are some items which are on both solder paste layer and solder mask layer, but they might be test points with independent pads. Some of them are supposed to have aperatures on stencil, but some not.

Example:

Tips：If this item needs to open on the stencil, you may leave a note in remark area. For example, 'Please make apertures on the stencil for test point pad XXX'.

4.Select appropriate valid area for the stencil.

The valid area should always be larger than the PCB size. If it is one stencil for both the Top and Bottom sides of the PCB, the valid area should be big enough for two sides.

5.Apertures for through hole pad

If you have apertures deisnged in solder paste layer for the through hole pad, please indicate whether the through hole should be avoided or not. If not, this might be an engineering question to confirm with you.