US 10,433,429 B2Granted

Method of enhancing fatigue life of grid arrays

AssigneeMassachusetts Institute of Technology

InventorsJames H. Kelly, Dmitry Tolpin, Roger M. Maurais

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Abstract

A method is presented that improves reliability for the mechanical electrical connection formed between a grid array device, such as a pin grid array device (PGA) or a column grid array device (CGA), and a substrate such as a printed circuit board (PCB). Between adjacent PCB pads, the method increases a spacing pattern toward the periphery of the CGA, creating a misalignment between pads and columns. As part of the method, columns align with the pads, resulting in column tilt that increases from the center to the periphery of the CGA. An advantage of the method is that the column tilt reduces the amount of contractions and expansions of columns during thermal cycling, thereby increasing the projected life of CGA. Another advantage of the method is that it reduces shear stress, further increasing the projected life of the CGA.

Claims12

Dependent claims

A method of assembling an electronic component onto a printed circuit board comprising:

providing the printed circuit board having a printed circuit board coefficient of thermal expansion;
placing an array of pads on the printed circuit board;
applying connective material to the array of pads;
providing the electronic component, having an array of conducting posts and a different coefficient of thermal expansion than the printed circuit board coefficient of thermal expansion;
placing the electronic component on the printed circuit board so that the array of conducting posts of the electronic component is misaligned with the array of pads;
mounting the electronic component to the printed circuit board by heating the connective material and positioning the array of conducting posts against the connective material on the array of pads with ends of conducting posts of the array of conducting posts being drawn into closer alignment with pads of the array of pads wherein the conducting posts of the array of conducting posts have an angular tilt outwardly away from a center of the electronic component to the printed circuit board;
and
maintaining the angular tilt outward of the array of conducting posts outwardly away from a center of the electronic component to the printed circuit board to a sufficient degree due to sufficient misalignment of the conducting posts with the array pads of the printed circuit board at 20 degrees Celsius and over a temperature range of 0 degrees Celsius to 100 degrees Celsius.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/270,940Filed 20 Sep 2016 · division
Priority: 23 May 2012
Published: US 2017/0013725 A112 Jan 2017
Granted: 1 Oct 2019
Term ends: Not estimatedThe source records don’t support an estimate.

Classification20 codes

H05K 3/301
Assembling printed circuits with electric components, e.g. with resistors: by means of a mounting structure
H05K 1/111
Printed elements for providing electric connections to or between printed circuits: pads for surface mounting, e.g. lay-out
H05K 1/18
Printed circuits: structurally associated with non-printed electric components
H05K 1/181
Structurally associated with non-printed electric components: associated with surface mounted components

Family

Application61/650,602Us provisional application · filed 23 May 2012
Application13/901,398Parent of this division · filed 23 May 2013
US 2017/0013725 A1Pre-grant publication · published 12 Jan 2017
US 9,491,859 B2Parent of this division
US 2013/0313007 A1Published application
US 10,433,429 B2This patent

From the US filing history. Foreign family members aren’t listed.