Paste in hole (sate of the art)

Hi,

I take it you are refering to intrusive reflow?

It came around as more components became available in surface mount packages leaving mainly connectors left over for a separate insertion operation & wave/selective/hand solder.

Manufacturers improved the thermal properties of their plastics allowing connectors to withstand reflow profiles, and paste was put down via 3D stencil, solder preform, dispensor etc, around & in the holes.

Then the paste down the hole to form a reasonable joint.

Take a look at Bob Willis' website, he always has something useful to say:

http://www.bobwillis.co.uk/5/5_6/5_6_2.htm

It's not "state of the art" though.

Good luck,

Rob.

reply »

You can also take a look at http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=9902&mc=2 /Mika

reply »

We design a broad range of DC/DC power supplies for various telecom, internet, and computor applications and have been succesfully using intrusive reflow for ~7 years now. Our pcbs range from 0.065 to 0.090 in thickness and are moslty dense 4 to 8 layer designs utilizing 1,2,3, and 4 oz. copper-layers plated up 1 oz. Most of theses designs have inter-layer connections to the pins. All of the assemblies are two-sided surface mount and the interface to the customer is generally PTH connectors or PTH pins that are either coined or turned, square or round, and range in diameters from 0.020 to 0.080 - The sqaure pins are friction fit into the walls of the barrels and the round pins have knurl features that provide the initial mechanical fit. The connectors are industry standard SAMTEC/TYCO/AMP with square and retangular shaped pins on 100 ceneters. These are not press-fit. For the paste-volume, we do the math, over-size the apertures and rely on the wicking-effect to from the solder-fill during second-side reflow. For the friction-fit pins, we do the math and ensure only the plating in the barrel comes into play, keeping the FR4 out of the way since we would violate IPC, customer desire, common-sense, and our machine capability. Naturally good mole-profiling and post cross-sectioning practices are a must to ensure you have a working reciepe. Please write if you would like more detail.

reply »