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Need SMT Expert's Help



Need SMT Expert's Help | 8 March, 2001

Hi, We are encountering a shortage on our parts and our purchasing said that the parts, which is in PLCC packaging, is hard to order from the local and international market and we can only get them in QFP packaging. Now the problem enters here. Our PCB land is designed for PLCC package and QFP won't fit in. As a temporary solution, our Design engineer designed a board that will fit the QFP (the board is in panel of 20 QFP's). The the process will be to machine place the QFP's on the panel and reflow them then depanelise the board then Machine place the Board with the QFP onto the PCB's PLCC land the reflow the board once again. The idea is like a converter board for the QFP to a PLCC land. Has anyone done this before? What possible problems might we encounter during the process? Will the QFP solderability pose a problem due to being reflow twice the it will pass the wave solder process afterwards. Note that we do not have time to change the Land design from QFP100 to PLCC68 as our customer needs the products badly and they are in quantity of 600 per week. Please help !

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Need SMT Expert's Help | 8 March, 2001

So much for the experts you asked for, Dreamer.

Your project is fairly common. As an expample, there was a thread in the past month or two on SMTnet, where someone was looking for suppliers of "adapters".

You should focus on: * Placing the adapter properly. Hit the target. Be gentle, do not splat the paste. And all that. * Soldering with zero voids * Avoiding rework.

Yano, you could search SMTnet, find the names of the suggested suppliers, call 'em, and ask you their suggestions on how best to go about this project, except, maybe buying stuff from them.

I not concerned about the reflow cycles that you are talking about. Umm, er, I assume then you talk about waving this pup, it'll be top side on the wave, right? If not tell me how it goes, never dun thet.

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Need SMT Expert's Help | 13 March, 2001

We had a similar issue with one of our products and ended up redesigning the whole PCB to fit the new parts. It may be little more costly up front than your solution, but should should have a much lower impact on quality and process and cost much less in the long run, depending upon volume of product produced.

This required some commitment on the part of our staff, but we had the whole thing up and running again within a week.

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Mike Naddra


Need SMT Expert's Help | 20 March, 2001

We have had a similar issues with some of our boards , However I took a different approach to the solution that I thought I would mention. There is a company Called Additive Services Inc. 603-889-1999. They have developed a process to screen lands and traces on to existing boards , they do this in accordance with IPC manufacturing standards , they offer an extremly fast turn around on orders of less than 100,000 boards and are very low cost. I had them extend the pads on one of my products as I could only get a narrow body SOIC and my land geometries were that of a wide body.

Hope this helps, Mike

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