dfm 20-5001-00000030

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DfM Report PCB : 20-5001-00000030 RevP00 Client : Thomas&Betts

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1. In order to properly orient the TH connectors with respect to the wave and to avoid

warpage of the board during wave soldering, the PCB must be oriented in the wave

soldering machine with J5 or J12 in the front. This makes that most SMT components on the

bottom side need to be rotated 90 degrees, just like C12 in order to be properly oriented, to

avoid skips.

2. Still in order to prevent skip solder, the SMT component pads need to be extended 0.010”

each towards the exterior, in order to allow for more wetting surface.

3. To avoid solder bridges on TH components, the annular rings of the TH parts have to be

adjusted so that the Cu to Cu spacing is 0.035”, in the case of RoHS products. J5, J10 -13, J16

and all the JPs, at minimum, need the annular rings to be decreased.

4. Many SMT pads need thermal relieving connections to Cu planes, in order to avoid excessive

heat during soldering and even higher heat, should rework be required. See red boxes in

Image 1 for examples of the mentioned situation. For calculus of thermal reliefs see IPC-

2222 paragraph 9.1.2. They are defined in IPC-2221, paragraph 9.1.3.

Image 1

5. Several polarized components, e.g. D5 and D7 have the polarity mark under the body of the

component, once it is installed, therefore not visible after assembly, see Image 2. Polarity

marks outside of the body is advisable.

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Image 2

6. The central pads of U1 and U2 have 0.013” via holes, see Image 3, that will drain a large

quantity of solder in reflow. This will create large voids in the central joint that may affect

the thermal or grounding properties. To limit draining, the vias should be 0.008” in

diameter.

Image 3

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7. Fab note 5 asks for 0.005” tolerance for the board thickness. As this is hard and costly to

obtain, I recommend a 10% tolerance request.

Disclaimer:

This report is the result of a visual inspection of mainly the top and bottom layers. This

inspection is not in any way exhaustive and points certain design issues that, if resolved, would

reduce the assembly costs or, in certain cases, improve the long term reliability of the product.

The component footprints are not all checked, but only a few of them, known problematic, are

verified according to the experience of the consultant or the IPC-7351B libraries.

The PCB manufacturing issues are, most likely, not all identified and a thorough computerized

analysis by a PCB manufacturer is recommended.

The interpretation and implementation of this document is at customer’s free will and Ioan

Tempea, ing., is not to be held liable to any expenses related to the said implementation.

dfm 20-5001-00000030

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